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Fertility history and health in later life: a record linkage study in England and Wales

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Page 1: Fertility history and health in later life: a record linkage study in England and Wales

ARTICLE IN PRESS

0277-9536/$ - se

doi:10.1016/j.so

�Correspondfax: +4420 729

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Social Science & Medicine 61 (2005) 217–228

www.elsevier.com/locate/socscimed

Fertility history and health in later life: a record linkage studyin England and Wales

Emily Grundy�, Cecilia Tomassini

Centre for Population Studies, London School of Hygiene and Tropical Medicine, 49-51 Bedford Square, London WC1B 3DP, UK

Available online 4 February 2005

Abstract

Women born at different periods within the 20th century in England and Wales have followed varying fertility

pathways with large changes in, for example, proportions having no children or only one child. Among the

consequences of these changes may be effects on women’s health later in life. Links between fertility histories and later

health and mortality have been investigated in several studies, but in many of these socio-economic characteristics have

not been allowed for, even though there are socio-economic differences in both fertility and mortality patterns and

results are conflicting. Here we analyse associations between the fertility histories of women born 1911–1940 in England

and Wales and their mortality and health status after age 50. We used data from the Office for National Statistics

Longitudinal Study; a record linkage study of approximately 1% of the population initially based on those enumerated

in the 1971 Census of England and Wales. We used survival analysis to investigate the effects of parity, short birth

intervals, and timing of fertility on mortality from age 50 to the end of 2000, controlling for a range of relevant socio-

demographic characteristics. For survivors to 1991, we additionally used logistic regression to model probability of

having a limiting long-term illness in 1991. We found that nulliparous women and women with five or more children

had significantly higher mortality than other women, and that in the oldest groups women with just one child also had

raised mortality. Women who had been teenage mothers had higher mortality and higher odds of poor health than

other parous women. Mothers with short birth intervals, including mothers of twins, also had elevated risks in some

cohorts. Late childbearing (after age 39) was associated with lower mortality.

Personal demographic history is an important factor to consider in analyses of health and mortality variations in later

life. More research is needed to further elucidate causal pathways.

r 2005 Elsevier Ltd. All rights reserved.

Keywords: Women’s health; Reproductive history; Life course; Parity; Birth intervals; England and wales

Introduction

The importance of life course influences on health and

mortality differentials in later life is increasingly

recognised, both because past experiences exert strong

influences on current circumstances and because accu-

e front matter r 2005 Elsevier Ltd. All rights reserve

cscimed.2004.11.046

ing author. Tel.: +4420 7299 4668;

9 4637.

ess: [email protected] (E. Grundy).

mulated stresses may have long-term influences (Wads-

worth, 1997; Blane, 1999; Kuh & Hardy, 2002).

Parenthood represents a major domain of most people’s

lives with substantial short and long-term implications.

Apart from the physiological and psychological effects

of pregnancy and childbirth, the health of both women

and men may be influenced by stresses, role changes and

changes in allocation of personal and family resources

associated with childrearing and by the emotional and

social support benefits of parenthood. Whether the

d.

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ARTICLE IN PRESSE. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228218

long-term balance of these influences has negative or

positive effects on health in later life is likely to depend

both on the fertility pathways followed and on the

context in which these take place. In this paper we

analyse associations between the fertility histories of

women in England and Wales born between 1911 and

1940 and their mortality and health status after the age

of 50.

Hypothesised links between fertility histories and health

There are a number of mechanisms which may

underlie associations between fertility histories and

health in later life. These include direct biological

effects, selection effects, and indirect effects such as the

relative costs and benefits of childrearing.

The direct effects of fertility on the later life health of

women include the physiological consequences of

pregnancy and childbirth. Apart from the risks of

childbirth itself, childbearing in historical populations

and contemporary less developed countries, has been

associated with risks of both short and long term

morbidity (Riley, 2003; Menken, Duffy, & Kuhn, 2003).

Additionally, there are well-established linkages between

some aspects of fertility patterns and certain diseases,

most notably breast cancer (associated with nulliparity

and delayed motherhood, Madigan, Ziegler, Benichou,

Byrne, & Hoover, 1995). More recently reproductive

histories have been linked with a range of later life

chronic diseases, although it is unclear whether repro-

ductive characteristics are risk factors for chronic

diseases in their own right or whether they ‘merely

reflect earlier exposures in childhood and adolescence

that are the direct determinants of chronic disease’(Rich-

Edwards, 2002).

Selection effects are undoubtedly important as socio-

economic characteristics are strongly associated with

nuptiality and fertility patterns on the one hand and

with health and mortality on the other, although both

the strength and the direction of these associations have

varied over time (Ni Bhrolchain, 1993; Donkin, Gold-

blatt, & Lynch, 2002). Possible ‘reverse causation’ effects

on fertility, including timing of motherhood, need

consideration as well. Poor health may restrict oppor-

tunities for marriage and parenthood and decisions

about subsequent childbearing (Kiernan, 1988, 1989).

Ability to conceive and deliver a child after the age of 40

may be an indicator of ‘slower’ ageing and overall better

health (Snowdon et al., 1989) and in some populations

variations in teenage fecundity, influenced by childhood

nutritional status, may also be relevant. The effect of

these selective processes will certainly have varied over

time and between social groups. For example, a

comparative study of teenage motherhood based on

analyses of the 1946 and 1958 British birth cohort

studies showed that teenage mothers in the later cohort,

when teen childbearing was rarer, had more unfavour-

able antecedent characteristics than in the 1946 cohort

(Maughan & Lindelow, 1997). Availability of medical

care and access to modern methods of birth control are

also likely to have resulted in important differences in

the operation of these selective processes.

Parenting experiences more generally may have

consequences for health. Parenting has many benefits,

but also costs. On the positive side parenthood may

enhance social networks, provide a positive social role

and a potential important source of social support,

especially in the longer term (Grundy & Shelton, 2001).

The costs of parenthood include reduced opportunities

for fulfilment of other roles, the stresses associated with

rearing children, and substantial economic costs (Gra-

ham, 1984; Joshi, 2002). The impact of these stresses is

likely to vary with socio-economic circumstances. For

example, research has shown high rates of depression

and stress in lone mothers but not in married mothers

whose mental and general health is better than that of

non-mothers (Harrison, Barrow, Gask, & Creed, 1999).

Certain fertility pathways, particularly early childbear-

ing and closely spaced births, may increase both

physiological and social and psychological stresses and

are known to increase risks of partnership disruption

which itself may have negative consequences for health

(Murphy, 1984).

Finally some evolutionary theories of ageing posit a

negative relationship between fertility and longevity

reflecting ‘trade offs’ in investment in younger-age

reproductive ‘fitness’ and somatic maintenance in the

post-reproductive period (Kirkwood & Rose, 1991).

Previous research on fertility patterns and health

Given the complexity of these hypothesised links

between fertility and health, it is perhaps not surprising

that results from empirical studies are in some respects

confusing or conflicting. These ambiguities may also

reflect the range of methods and populations studied

and inability in many of them to control for important

interactions with socio-economic and socio-demo-

graphic characteristics. Several studies of historical

populations have reported links between parity, espe-

cially high parity, and later life mortality. Westendorp

and Kirkwood (1998) reported a negative association

between number of children borne and mortality after

the age of 60 for both female and male members of the

English aristocracy, although concerns about the quality

of the data used in this analysis have been raised

(Gavrilov & Gavrilova, 2002). An analysis of the

mortality of Southern Californians born 1880–1929 also

showed a negative relationship between parity and

survival among women, but not men (Friedlander,

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ARTICLE IN PRESSE. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228 219

1996). A study of Danish twins born 1893–1923 used

dentition at age 73 or over as the outcome measure

(tooth loss being a well established indicator of

cumulative nutritional strain) and found a positive

association between parity and tooth loss—those with

more children had fewer remaining teeth—and an

interaction with socio-economic status (Christensen,

Gaist, Jeune, & Vaupel, 1998). Other historical studies,

however, have found multiparous women had better

post menopausal survival than women with no or only

one child or that the direction of the association

depended on whether duration of marriage was taken

into account (Lycett, Dunbar, & Voland, 2000; Muller,

Chiou, Carey, & Wang, 2002).

Results from studies of more recent populations are

also sometimes conflicting. Some report higher mortality

among parous than nulliparous women; others the

reverse (Beral, 1985; Green, Beral, & Moser, 1988).

Several studies suggest nulliparity and high parity are

associated with higher risk (Kvale, Heuch, & Nilssen,

1994). These, include research by Doblhammer (2000),

whose analysis was based on Office for National

Statistics (ONS) Longitudinal Study data for England

and Wales and the 1981 Austrian census with linked 1

year follow up of deaths. However, this study was

restricted to ever-married women (as were several of the

others cited above) and the only socio-economic

indicator allowed for was presence/absence of higher-

level educational qualifications which is a poor dis-

criminator of socio-economic status in the current older

female population (Grundy and Holt, 2000). Moreover

only three parity groups were contrasted; the nullipar-

ous, those with one or two children, and mothers of

three or more children. Kington, Lillard, and Rogowski

(1997) in a study of a contemporary US population,

which they reported was the first in which associations

between reproductive history and health, rather than

mortality, were examined found that higher parity

women aged 50 and over had worse health compared

with nulliparous or low parity (1–2) women but

emphasised that their findings needed verification using

other data. Grundy and Holt (2000) using data from the

British ONS Retirement Surveys, found that parity was

associated with health and disability in early old age, but

sample size was relatively small and findings were

suggestive rather than conclusive.

Timing of childbearing, as well as number of children,

has been associated with health in later life in some

studies. Very early childbearing has been linked with a

range of negative outcomes, including poorer health

(Maughan & Lindelow, 1997) and, in poorer countries,

impaired growth (Riley, 1994). Few studies have looked

beyond health in early or mid life, although Grundy and

Holt (2000) found that self reported health among

women aged 55–74 was negatively associated with birth

before age 23 (taking account of socio-economic

circumstances) and in Doblhammer’s analysis ever

married women who gave birth before 20 had a higher

mortality risk at ages 50–85 than other parous women.

The possible effects of late childbearing on health and

mortality at older ages are more controversial. In the

study of English aristocrats referred to above, women

who gave birth after the age of 40 had better survival

after age 60 (Westendorp & Kirkwood, 1998); a number

of other studies have reported similar findings (Perls,

Alpert, & Fretts, 1997). This includes a recent study of

very old women and men in China in which childbearing

after age 35 or 40, particularly having several children

after these ages, was positively associated with both

good health and survival from ages 80–85 to very old

age (Yi & Vaupel, 2004). In contrast, a recent study

from the US reported associations between late child-

bearing (first birth after age 35) and a range of adverse

health indicators after the age of 50 including diabetes,

hypertension, congestive heart failure, poor dental

health, vision difficulties and impaired physical mobility

(Alonso, 2002). Consistent with this, a long-term follow

up of college women in the US found that women who

gave birth after the age of 40 had the highest mortality

risk (Cooper, Baird, Weinberg, Ephross, & Sandler,

2000).

One further aspect of fertility history which may be

associated with health in later life is birth spacing. In the

developing country context, it has been hypothesised

that closely spaced births may be associated with a risk

of maternal depletion and consequent poorer health,

although evidence on this is inconclusive (Menken et al.,

2003). Longer term implications of short birth intervals

have not, however, been examined.

Changes in fertility patterns in England and Wales

Improving our knowledge and understanding of

associations between fertility histories and health and

mortality in mid and later life is particularly important

in the current context of population ageing and

substantial changes in partnership and parenting his-

tories over the course of the 20th century in England and

Wales and elsewhere. Period total fertility rates (TFRs)

in England and Wales fell to a low point of 1.8 in the

second half of the 1930s before rising to a peak of 2.9 in

1964 and then falling again to a second low point in the

second half of the 1970s (OPCS, 1987). A slight

‘recovery’ in fertility in the early 1980s was followed

by a further fall and in 2001 the TFR fell to the lowest

level ever recorded (1.64). Viewed from a cohort

perspective, there have been large changes in the

proportions never-marrying, remaining childless and,

among parous women, in distribution by family size and

in timing of fertility. Thus some 15% of women born in

1900 were never-married by age 50 and results from the

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1951 census suggest that as many as a third of women in

these very early twentieth century cohorts remained

childless (Werner, 1987; Grundy, 1996). Among those

born in 1935, by contrast, fewer than 5% were never-

married by age 50 and only 11% remained childless.

Changes in the timing of fertility have also been

substantial. Age specific fertility rates for women aged

40 and over exceeded those of teenagers, often

substantially, until the 1940s. By 1971, however, teenage

age specific fertility rates (51 births per 1000) were five

times higher than those of the 40 and over group (9 per

1000) (Werner, 1987). More recent cohorts show a

‘return’ both to later ages of childbearing and a high

prevalence of childlessness, but in the context of more

diverse, and disrupted, partnership arrangements.

Research questions

These historical changes mean that there are con-

siderable differences in the fertility histories of women

who are now of advanced age, in early old age or mid

life. The consequences of these variations for support in

old age are recognised to be important. In this paper we

investigate whether there are also consequences for

health status in later life, which is a major influence on

needs for support. We use data from a nationally

representative record linkage study from England and

Wales, the Office for National Statistics Longitudinal

Study (ONS LS) to analyse associations between fertility

history and an indicator of health status in mid or later

life and mortality after age 50 among women born

between 1911 and 1940. As reported above, this data set

was used by Doblhammer (2000) to investigate the

mortality of 56,000 ever-married women aged 40–59 in

1971 during the period 1971–1996. Our analysis extends

this work in several important ways. Firstly, we include

more adequate control for socio-economic characteris-

tics by using measures of housing tenure, car access and

occupationally based social class, as well as the

educational qualification indicator used in Doblham-

mer’s analysis (which is of very limited use as 92% of the

women in the cohorts considered in Doblhammer’s

analysis fell into the ‘basic’ qualification group); we also

control both for baseline marital status and for

subsequent widowhood. Secondly we include all women,

not just those who were ever-married in 1971 and so our

analysis of associations between nulliparity and later

health compares all nulliparous women with all parous

women, rather than just nulliparous ever-married

women with parous ever-married women. Thirdly, by

making use of linked birth data we extend the analysis to

all women born between 1911 and 1940 and alive in

1971; use of linked birth data also improves capture of

births after 40 among the earlier cohorts. Fourthly, we

examine the possible effect of short birth intervals on

later life mortality and health and analyse associations

between parity and mortality in greater detail, rather

than using aggregated categories. Thus we compare

women with 0, 1, 2, 3, 4, and 5 or more births, rather

than collapsing parous women into those with one or

two births and those with three or more. Fifthly, as well

as analysing associations between teenage and late

(439) childbearing, we also examine variations accord-

ing to age at first and last birth across the distribution.

Finally, we include presence of limiting long-standing

illness in 1991 as an outcome measure, as well as

mortality 1971–2000.

The specific research questions addressed are whether

early childbearing and closely spaced births are asso-

ciated with worse health outcomes in mid and later life,

even after control for socio-economic characteristics;

whether overall parity is associated with later life health

outcomes (again allowing for socio-economic character-

istics); whether late childbearing has positive or negative

associations with later health and mortality and whether

these effects vary between cohorts.

Data and methods

The ONS LS is a record linkage study of approxi-

mately 1% of the population initially based on those

enumerated in the 1971 Census of England and Wales

(approximately 500,000 people). Sample members were

traced in the National Health Services Central Register

(NHSCR) and record linkage used to add information

from subsequent censuses and from vital registration,

including births to sample mothers, death of spouse, and

death. The LS has been maintained through the addition

of 1% of new births and immigrants, but our analyses

here are based on follow up of women from the initial

1971 sample. We selected all women present in the 1971

census sample and then aged 31–59 (birth cohorts

1911–1940). In most of the analysis we have divided

these women into three groups born in 1911–1920,

1921–1930 and 1931–1940 respectively. These cohorts

were chosen as our interest is in possible associations

between fertility history and health and mortality in the

post reproductive period. We therefore wanted to

include only those we could observe for a reasonable

period after the age of 50. Women who were aged 60 or

over in 1971 (born before 1911) could not be included as

no fertility data were available for them.

The fertility history data come from a combination of

1971 Census and subsequent vital registration informa-

tion. The 1971 Census included questions on the marital

and fertility histories of ever-married women; subse-

quent linkage of births to sample mothers (of all marital

statuses) is currently complete to the end of 2000, as is

linkage of deaths of sample members and their spouses.

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ARTICLE IN PRESS

Table 1

Parity distribution of women born in 1920 and women born in

1940: comparison of results from the LS sample and from

official statistics

Parity Birth cohort 1920 Birth cohort 1940

LS Official

statistics

LS Official

statistics

0 22 21 13 11

1 24 22 13 13

2 26 27 36 36

3 16 16 22 22

4+ 12 14 16 18

Sources: Official statistics from ONS (2002); ONS Longitudinal

Study, authors’ analysis.

E. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228 221

For the women included in this analysis we therefore

have near complete fertility histories to the end of the

reproductive period. There are, however, some sources

of potential omission. The first arises because in 1971

only ever-married women were asked to provide fertility

history data and they were only asked to record births

within marriage. We therefore have no data on non-

marital births prior to 1971. For cohorts born between

1920 and 1940, non-marital fertility generally accounted

for only 4–6% of all births in England and Wales, so the

effect of this omission is relatively slight (OPCS, 1987).

A second minor problem relating to the census data is

that a small proportion of ever-married women neither

entered dates of birth of children nor wrote ‘none’ on the

fertility section of the census form, as women without

children were instructed to do. We have assumed here

that these women were childless, an assumption

supported by post-enumeration quality checks on the

1971 Census which found that a quarter of childless

women left the fertility history section of the form blank

(Hattersley & Creeser, 1995). We additionally checked

the household data for these women to ensure they had

no children living with them and analysed their

characteristics and subsequent mortality, which we

found to be very similar to that of women definitely

known to be childless. The effect of this may be that we

slightly overestimate childlessness, but the proportions

involved are relatively small (2–4% of women in the

three birth cohorts we examine). Post 1971 fertility

information comes from linkage of births, both marital

and non-marital, and some births may have been missed

due to linkage failure, estimated to be around 8–9%

(Hattersley & Creeser, 1995). As a check on the validity

of the fertility history data, we compared the parity

distributions we derived for LS members born in 1920

and 1940 with official ONS figures derived from vital

registration for the whole population. As can be seen

(Table 1) this suggests a slight overestimation of

childlessness and underestimation of high parity in the

LS but an overall close correspondence. The slight

differences in proportions childless, especially for the

1940 cohort, probably reflects the fact that the LS data

do not capture non-marital births prior to 1971.

Linkage rates of deaths in the LS are better than for

births and it is estimated that only 1% of deaths are

missed (this difference partly reflects the fact that there

are two independent methods for linking deaths). In

addition to mortality, we use presence of limiting long-

standing illness, as reported in the 1991 Census, as an

outcome measure.

We excluded from the study women who were

identified as potential members of the LS from the

1971 Census but not traced in the NHSCR; known

emigrants; and those lost to follow up (not found in

subsequent censuses and with no event records—many

of these are thought to be emigrants). A few other cases

with discrepancies in dates or implausible ages at giving

birth (o11 or 454) were also excluded leaving a final

sample of 87,246 women. These exclusions amounted to

5.5% of the initial sample. We also had to exclude from

the mortality analyses the small proportions of women

resident in institutions in 1971 (o2%), as information

on relevant co-variates was not available for them. For

the same reason we excluded from the analysis of

variations in longstanding illness in 1991, 1.4% of

women who were then in institutions.

We used survival analysis to investigate the effects of

parity and spacing and timing of fertility on late-adult

mortality controlling for a range of relevant socio-

demographic and socio-economic characteristics in

1971. These co-variates were marital status (at 1971

but adjusted for subsequent widowhood); social class

based on own current or past occupation (manual, non-

manual, no occupation); housing tenure (owner occupier

versus tenant) and car access (household has use of car/

no use of car). We also included an indicator of

educational status. However, the 1971 Census only

collected information about qualifications equivalent to

or higher than ‘A’level’ (a school qualification gained at

around age 18) so this variable only distinguishes a small

minority of the population from the rest. The distribu-

tion of the three cohorts by these characteristics is

shown in Table 2 (the table also shows the proportion

excluded because of institutional residence). Those born

in 1911–1920 were aged 51–60 in 1971 whereas the

1931–1940 cohorts were only aged 31–40: variations in

the distributions reflect both these age differences (for

example, differences in the proportions who were

widows) and cohort differences (for example, the higher

proportion of women with an educational qualification

in later born cohorts).

Our analyses are restricted to women who survived to

age 50. Estimates from the Government Actuary’s

Department indicate that of girls born in 1911 who

survived to age 15, 9% died between their 15 and 50

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ARTICLE IN PRESS

Table 2

Distribution of the sample by grouped birth cohort and 1971

characteristics included in the analysis

Characteristics in

1971

Birth cohort

1911–1920

(%)

1921–1930

(%)

1931–1940

(%)

Marital status

Single 9.1 7.2 6.9

Married 78.0 87.1 90.0

Divorced 2.1 2.2 2.3

Widow 10.8 3.5 0.9

‘A’level’+a,b 7.3 9.1 12.7

Non manual social

classb25.1 31.6 26.6

Manual social classb 33.3 30.7 23.8

Not workingb 41.5 37.7 49.5

Household has

access to carb55.5 66.2 69.2

Owner occupierb 50.1 51.7 58.3

In institution 1.7 1.0 1.1

N 30 599 30 442 26 436

Source: ONS Longitudinal Study, authors’ analysis.a‘A’level’; A’level equivalent, or higher qualification (quali-

fications gained at 18+).bNo information on these characteristics available for those

in institutions in 1971.

E. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228222

birthdays; equivalent proportions for the 1921 and 1941

cohorts were 7% and 4%. This means that if, for

example, high parity women had greater risks of dying

before 50 (which may particularly apply in the oldest

cohort) we may slightly underestimate risks associated

with high parity.

We firstly examined the risk of dying from age 50 until

the end of 2000 for the 1911–1920, 1921–1930 and

1931–1940 birth cohorts, separately. The length of

observation for each cohort varied, thus we observed

the earliest from age 50 to age 80–89 and the last only

from age 50 to age 60–69. Secondly we ran the analysis

with a pooled sample, with censorship at 31st December

2000 or at age 70 and an additional control for cohort

(as the three cohorts were aged 50–69 during different

periods in which mortality risks varied considerably).

The model specified is shown below

logit ðlitÞ ¼ aðtÞ þ b1X i1 þ b2X i2ðtÞ;

where t is survival time, measured in years, starting from

age 50, lit is the probability of death of a woman i in

year t, given that she was alive at year t�1, Xi1 are the

time constant covariates (socio-economic indicators at

1971 census, fertility measures) of the woman i, and b1their coefficients to be estimated, and Xi2 are the time-

varying covariates (widowhood) of the woman i, and b2their coefficients to be estimated.

We use discrete-time event-history models where the

year is the time unit because for confidentiality reasons

only year of birth, not day and month, is available for

analysis.

We additionally used logistic regression to model

probability of having a limiting long-term illness in

1991, for those who survived to 1991, controlling for

characteristics in 1991, and for changes in marital status,

car ownership and housing tenure between 1971 and

1991.

Results

Fertility characteristics and differentials in survival

In this section, we consider the fertility characteristics

of the cohorts of interest and, in order to assess any bias

arising from linkage failure and the other problems

referred to above, make some comparisons with results

from other sources. We then present the results of

survival analysis undertaken for each cohort separately

and then for a pooled cohort observed from ages 50–69.

Table 3 shows indicators of the fertility histories of the

three cohorts considered and also the odds ratios for

mortality by the fertility indicators for the three grouped

cohorts studied.

Looking first at the fertility characteristics of the three

cohorts considered, it can be seen that these vary very

considerably. The oldest cohort, born 1911–1920,

included a relatively high proportion who never married

or married but had no children (26%), and a high

proportion with only one child (23%) while only 15% of

the women born in 1931–1940 remained childless and

14% had one child only. Mean age at birth of the first

child decreased consistently across the three cohorts

from 26.8 to 24.7, as did mean age at birth of the last

child, from 32.1 to 30.1. The latest born cohort included

a much larger proportion of teenage mothers compared

with the earliest cohort, but only 3% of parous women

who had a child at age 40 or older, compared with 10%

of mothers born 1911–1920. Overall fertility increased in

successive cohorts as did the proportion who had at least

one intergenesic interval (interval between births) of 18

months or less. The proportion of women who had had

twins showed no cohort variation, which is reassuring as

we would not expect variation in this.

Our estimates of cohort TFR for the 1921–1930

cohorts combined is 1.9 and that for 1931–1940 is 2.2

whereas official estimates are 2.1 and 2.4 respectively

(Office for Population, Censuses & Surveys, 1987; ONS,

2002). It is harder to test the validity of results for

women born before 1920 as information on prior births

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Table 3

Distribution of women by fertility characteristics (at the end of the reproductive period) by grouped birth cohort, and results from the event history model for mortality after age 50

Birth cohort

1911–1920 1921–1930 1931–1940

Parity Sample (%) Adjusted OR (95% CI) Sample (%) Adjusted OR (95% CI) Sample % Adjusted OR (95% CI)

All women

0 26.0 1.13** (1.08–1.18) 20.7 1.22** (1.14–1.31) 15.0 1.28** (1.10–1.49)

1 23.0 1.06** (1.02–1.11) 19.8 1.04 (0.98–1.11) 13.7 1.10 (0.96–1.27)

2 (ref) 26.0 1.00 28.8 1.00 33.4 1.00

3 13.5 1.01 (0.96–1.06) 16.0 0.99 (0.93–1.07) 21.1 1.01 (0.89–1.15)

4 5.8 1.05 (0.98–1.12) 7.6 1.01 (0.92–1.11) 9.6 1.11 (0.95–1.30)

5+ 5.7 1.14** (1.06–1.22) 7.0 1.12* (1.02–1.22) 7.2 1.25** (1.06–1.46)

TFR 1.70 1.94 2.20

Number of deaths 18 495 8622 2212

Percentage of cohort dead

between age 50 and end 2000

60.4 28.3 8.4

N 30 599 30 442 26 436

Parous women

Had a child agedo20 4.4 1.15** (1.06–1.25) 4.7 1.16* (1.04–1.29) 7.5 1.30** (1.11–1.53)

Had a child aged439 10.2 0.93* (0.87–0.99) 7.9 0.89* (0.81–0.98) 3.1 0.94 (0.72–1.22)

Had an intergenesic intervalo18

months

11.6 1.19** (1.12–1.26) 15.2 1.01 (0.93–1.09) 19.2 1.08 (0.94–1.23)

Had twins 2.4 1.13* (1.01–1.27) 2.5 1.12 (0.97–1.31) 2.4 1.19 (0.90–1.56)

Mean age at first birth 26.8 (SD 5.0) 25.7 (SD 4.6) 24.7 (SD 4.3)

Mean age at last birth 32.1 (SD 5.5) 31.3 (SD 5.6) 30.1 (SD 4.7)

N 22 642 24 138 22 477

Results from fully adjusted models controlling for age, marital status, social class, education, car access and housing tenure (all in 1971) and widowhood post 1971, excluding women

in institutions in 1971 (but including those who later moved to an institution).

*Po0:05; **Po0:01:Source: ONS Longitudinal Study, authors’ analysis.

E.

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223

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ARTICLE IN PRESSE. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228224

was not collected via the birth registration system

until 1938 and retrospective data for these cohorts

have not been collected in the national survey used to

produce official estimates (the General Household

Survey). However the results found here are consistent

with earlier estimates made by Grundy (1996) on the

basis of the 1951 Census, although the proportion

childless appears slightly higher than expected and the

overall level of fertility, as in the later cohorts, slightly

too low. These slight differences probably reflect

exclusion of a few pre 1971 non-marital births and the

known slight incompleteness of linkage of births after

1971.

In the analysis of associations between fertility

characteristics and mortality risk, we present odds ratios

of death by the characteristics of interest from models

including the socio-demographic control variables

discussed earlier. Odds ratios for these control variables

are not shown, in the interests of simplifying the

presentation, but are available from the authors on

request.

The upper section of Table 3 shows the results

obtained in the model run on all women, while the

lower presents results from analyses of the mortality of

parous women. In all three cohorts childless women and

women with five or more children have consistently

higher risks of mortality than women with two children,

even after controlling for other demographic and socio-

economic factors. Risks for mothers of three children

were identical to those of mothers of two and risks for

mothers of four children were only raised in the

youngest cohort (and not significantly so). In the

1911–1920 cohort there is additionally a significant

excess risk for those who had only one child (odds ratios

for mothers of one child only were also raised in the later

cohorts, but did not reach conventional levels of

statistical significance).

The lower part of Table 3 includes the results of the

survival analysis run on parous women. Having a child

before age 20 was consistently associated with a higher

mortality risk and having a child after age 40 was

significantly associated with lower mortality for the

cohorts born between 1911 and 1930. The reference

category in both these cases is a wide one—women aged

20–39. We investigated effects of age at childbearing in

more detail by analyzing variations in mortality risks by

age group at first and age group at last birth, using 10

year age groups. These results, not shown here but

available from the authors, showed that those who

became mothers before 20 had a higher mortality risk

than women who had their first birth in their 30s, but

there was no difference between 20 and 29 year old first

time mothers and those aged 30–39 or 40 or more.

Results for age at last birth showed, again consistent

with results for all births, an advantage for mothers

whose last birth was at age 40 or over. Additionally,

among women born between 1911 and 1930, those who

had their last child in their 30s had a slightly lower

mortality risk than those who completed their child-

bearing before the age of 30.

Among women born 1911–1920, having a multiple

birth or other short birth interval was also associated

with higher mortality. The smaller number of deaths

among later born women means that fewer results are

likely to be statistically significant.

Fig. 1 shows the results from the pooled model of

mortality between age 50 and 69 for all three cohorts. As

in the cohort specific analysis, nulliparity, high parity

and early childbearing were associated with increased

risks, as were having one child only, having a multiple

birth or having a short birth interval. There were of

course also large differences between the cohorts in

mortality risk in the age groups considered reflecting the

substantial improvements in mortality over the period.

We had hypothesised that the effects of the fertility

parameters considered might vary between the cohorts

as a result of, for example, differences in selective

factors, such as differences in chances of getting married,

and period differences in antenatal and obstetric care.

We accordingly fitted various interaction terms, but as

none were statistically significant these were not

included in the final model.

Health status in 1991

The 1991 Census included a question on presence of

limiting longstanding illness and in the final part of our

analysis we used a logistic regression model to examine

associations between fertility characteristics and this

outcome. Women included in this model had to have

survived to 1991 and of course different birth cohorts

were at different ages, ranging from 51 to 80, at this

date. We also had to exclude those in institutions in 1991

as information on co-variates was lacking for this group.

Those excluded because of institutional residence

accounted for 4.2% of those born 1911–1920, 3.1% of

those born 1921–1930 and 2.4% of those born

1931–1940. In addition to the socio-economic variables

in 1971 Census, we also controlled for changes in the

period 1971–1991 in marital status, in tenure type and

car access (e.g. if a woman changed from being married

to unmarried or from being a owner to being a renter).

Results, presented in Table 4, show that in all three

cohorts, having had five or more children was associated

with a higher risk of long term illness in 1991, as was

having had a teenage birth. In the youngest cohort born

1931–1940 and aged 51–60 in 1991, nulliparity was also

a risk factor. Among parous women, having had a short

birth interval was positively associated with long term

illness, and having had a child at age 40 or later was

associated with reduced risk.

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ARTICLE IN PRESS

Spacing < 18 months

Child after 40

Had twin

Child before 20

Parity 5

Parity 4

Parity 3

Parity 2

Parity 1

Parity 0

OD

DS

RA

TIO

S an

d 95

% C

I

1.4

1.2

1.0

0.8

Fig. 1. Odds ratios and 95% confidence intervals, from the event history model for mortality between ages 50 and 70, pooled cohorts.

Controlling for age, marital status, cohort, social class, education, car access, housing tenure (all in 1971), and period, excluding

women in institutions in 1971 (but including those who moved to an institution subsequently).

E. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228 225

Discussion

This analysis of data from a large nationally

representative study of women in England and Wales

lends support to hypotheses of links between fertility

histories and health in mid and later life. In analyses

including controls for indicators of socio-economic

position and socio-demographic status, we found higher

risks of adverse outcomes among nulliparous than

parous women; higher risks associated with high parity

and closely spaced births; and associations between

teenage childbearing and childbearing at age 40 or more

with health and mortality in later life.

In all the cohorts we considered, nulliparity was

associated with higher risks of mortality. This is

consistent with results from a number of studies, but

not with those of some historical studies which have

suggested lower mortality among the nulliparous. It is

possible that we have slightly overestimated the effect of

nulliparity, as some women who had a non-marital birth

prior to 1971, a group likely to have ‘risky’ lifestyles,

may have been misclassified as nulliparous. However,

this bias should be relatively small, because as, noted

earlier, non-marital childbearing was low in the period

considered, and because to be misclassified as nullipar-

ous, such mothers would have had to have had no

subsequent children in marriage (or outside of marriage

post 1971). The greatest excess risk was observed in the

youngest cohort, which included the lowest proportion

of nulliparous women, and it was only in this group that

nulliparity was associated with higher odds of reporting

limiting long-term illness. This is consistent with the idea

that selection effects may partly account for the higher

risk, as the nulliparous will include those with health

problems which make marriage or motherhood less

likely and women with these characteristics may account

for more of the nulliparous group in cohorts in which

nulliparity is rarer. However, other factors are likely to

be important as well. These include higher risks of

specific diseases, notably breast cancer; an effect we will

examine in later cause-specific analyses, and lack of

social support from children.

Poorer outcomes were also observed for women with

one child only, although in the case of mortality this was

only significant in the oldest cohort and in the case of

long-standing illness, only in the middle cohort. Again

selection effects may be important, as those with one

child only will include women with health problems,

including problems related to first pregnancy, which

prevented or discouraged them from having more

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ARTICLE IN PRESS

Table 4

Odds ratios from logistic regression model of presence of limiting long term illness in 1991

Birth cohort

1911–1920 (aged 71–80 in 1991) 1921–1930 (aged 61–70 in 1991) 1931–1940 (aged 51–60 in 1991)

OR 95% Wald CI OR 95% Wald CI OR 95% Wald CI

All women

0 0.96 (0.88–1.05) 1.04 (0.95–1.14) 1.18** (1.04–1.33)

1 1.04 (0.96–1.13) 1.10* (1.01–1.20) 1.04 (0.92–1.17)

2 (ref) 1.00 — 1.00 — 1.00 —

3 1.04 (0.94–1.15) 1.04 (0.95–1.13) 0.99 (0.89–1.10)

4 1.12 (0.98–1.29) 1.00 (0.88–1.12) 1.10 (0.97–1.25)

5+ 1.26** (1.10–1.44) 1.22** (1.08–1.37) 1.33 (1.16–1.52)

Percentage with

long-term illness

39.1 25.6 16.3

N 19 095 24 977 24 233

Parous women

Had a birth

agedo20

1.30** (1.10–1.55) 1.37** (1.18–1.59) 1.41** (1.23–1.61)

Had a birth

aged439

0.93 (0.83–1.05) 1.02 (0.91–1.16) 0.65** (0.51–0.82)

Had an

intergenesic

interval o18

months

1.04 (0.92–1.18) 1.08 (0.98–1.20) 1.15** (1.03–1.29)

Had twins 0.90 (0.71–1.13) 1.14 (0.93–1.40) 0.92 (0.71–1.19)

Controlling for age, marital status, social class, education, car access and housing tenure (in 1991) and changes in marital status, car

and home ownership in the period 1971–1991.

*Po0:05; **Po0:01:Source: ONS Longitudinal Study, authors’ analysis.

E. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228226

children. Lower levels of social support may also be a

factor for those with one child only, as well as the

childless. Mothers who have only one child, for example,

are less likely to see a child at least once a week than

mothers with two or more children (Tomassini et al., in

press).

We found that women with three births had no

greater risk of mortality or longstanding illness than

mothers of two children, and there was no statistically

significant difference between mothers of four children

compared with mothers of two. However women with

parities of five or more had consistently elevated

mortality risks and higher odds of reporting limiting

long term illness in 1991. This suggests a ‘threshold’

rather than an additive effect and demonstrates the

importance of disaggregating parity as far as possible.

We also found risks of higher mortality, and in the

earliest cohort, of poor health, associated with having

twins and short birth intervals. A large literature on

links between fertility and maternal health in less

developed countries has considered adverse conse-

quences of short birth intervals for mothers as well as

children, but not definitively shown it for the former,

and this issue has been rarely examined in developed

countries. The associations between high parity and

closely spaced births (including twins) and later health is

consistent with the hypothesis of maternal strain, both

physical and psychological, arising from the stresses of

pregnancy and childrearing, especially rearing of more

than one young child at once.

Our results also indicate long-term health effects of

teenage childbearing. Odds ratios for mortality after age

50 among teenage mothers were 1.15 (1.06–1.25) in the

1911–1920 birth cohort, 1.16 (1.04–1.29) in the

1921–1930 cohort and 1.30 (1.11–1.53) in the youngest

cohort born 1931–1940. Excess risk of mortality for the

two earlier cohorts is less marked than in Doblhammer’s

analysis (1.26 for those born 1911–1920) because we

include greater control for confounding socio-economic

factors. Women who had a child before twenty and who

survived to 1991 also had 30–40% higher odds of then

reporting limiting long-standing illness. It is interesting

that in our analysis the effects of teenage childbearing

appear as great, or indeed greater, in the youngest

cohort as in the earlier ones even though teenage

mothers were relatively most numerous, and therefore

less ‘selected’ in this later cohort. We also would have

expected to find larger effects in the earlier cohorts

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ARTICLE IN PRESSE. Grundy, C. Tomassini / Social Science & Medicine 61 (2005) 217–228 227

because one pathway from teenage childbearing to

poorer later health may be through physiological effects

particularly affecting poorly nourished young women or

women who had not completed their own physical

growth. We would have expected such influences to be

most important in the oldest cohort who, as a group,

would have experienced more hardship in childhood and

young adulthood and later physical maturation than

later born women.

Our results generally support those studies which have

reported a negative association between late child-

bearing and both mortality and poor health—most of

which have been undertaken on either historical

populations or in contemporary less developed popula-

tions—in contrast to the results reported from con-

temporary US populations. Selection effects are likely to

be an important explanation for this association. A

precondition of late childbearing is continuing physio-

logical ability to become pregnant and carry a baby to

term. Although permanent cessation of menses generally

occurs in the late 40 s or early 50 s, fecundity (ability to

bear a child) starts to decrease well before actual

menopause (Rahman & Menken, 1993). Smoking is a

risk factor for earlier menopause and earlier menopause

is associated with higher subsequent mortality (McKin-

ley, Bifano, & McKinley, 1985). However, feeling

physically well and ‘young’ enough for motherhood at

40 plus is probably a more important influence than the

constraining one of continuing fecundity, especially in

the youngest cohort considered who would have had

access to modern contraceptive methods and legal

abortion. Differentials in social support may also be

important. The late born children of mothers in the

youngest cohort would for the most part still have been

at home in 1991 and for at least part of the mortality

follow-up period. As having multiple roles appears to be

positively associated with health in mid life women, this

in itself may have had a positive influence on health

(Hibbard & Pope, 1991; Adelman, 1994). Interestingly

we again found little evidence of differences between the

cohorts we considered in the direction of these associa-

tions, even allowing for interactions, despite large

differences in the fertility characteristics of these

cohorts. Overall the consistency of associations in all

the cohorts considered suggests that biological factors

may play an important part in associations between

childbearing histories and health in mid and later life.

As already noted, there are some limitations to our

analysis. Firstly it is probable that between 5% and 10%

of births were not captured either through omission of

pre 1971 non-marital births or linkage failures in the

post 1971 period. Secondly, we have no information on

childhood characteristics and indeed only socio-eco-

nomic and socio-demographic information for points of

time well into adulthood. Additionally, we have no data

on physical measures of health or on psychological

characteristics which may be associated with both

fertility and health trajectories. In particular early

motherhood, which here appears to have long lasting

negative effects on health, may be associated with

characteristics and behaviours, including smoking,

which we have been unable to control for. This points

to the need for analyses including detailed information

on antecedent characteristics and we are now engaged in

collaborative work using data from the British 1946

birth cohort study in order to investigate this further.

Despite these caveats, we believe our results lend

powerful support to arguments that personal demo-

graphic history is an important factor to be considered

in analyses of health and mortality variations in later life

and, more particularly, that differing fertility histories

may have long reaching consequences.

Acknowledgements

The work reported here was supported by the

Economic and Social Research Council, UK, Grant

Reference Res-000-0394. We are grateful to the Office

for National Statistics for access to data from the ONS

Longitudinal Study; the project was approved by the

Longitudinal Study Research Board.

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