Cold and Health

James Goodwin

Head of Research

Hippocrates 400BC

• Whoever wishes to investigate medicine properly, should proceed thus: in the first place to consider the seasons of the year, and what effects each of them produces for they are not at all alike, but differ much from themselves in regard to their changes.

• Secondly he must study the warm and the cold winds, both those which are common to every country and those peculiar to a particular locality …

On airs, waters, and places

Five Vital Questions

• Why does health deteriorate in the winter?

• Does age make a difference?

• What is ‘Excess Winter Mortality’?

• What are its causes?

• Can we do anything about it?

(1) Why does health deteriorate in the winter?

Why does health deteriorate in the winter

• Ill-health is associated with a number of winter factors, notably reducing photo-period and cold temperature

• We have tropical physiology

• Darkness is associated with emotional responses and mental health

• Cold is associated with physical and psychological responses

(2) Does age make a difference?

Does age make a difference?

• Vulnerability to cold increases with age:– Declining immune system– Lower physiological reserve– Slower and less precise bodily responses,

particularly temperature control, respiratory and cardio-vascular systems

• The change is progressive and variable but real decrements start at about 75 years and accelerate thereafter

Cold Exposure and Physiological Responses I

Young subjects

(n=11)

Old subjects(n=11)

Cold Exposure and Physiological Responses II

Young subjects

(n=11) •

Old subjects

(n=11) ◦

Skin Temperature (Finger) in Young (n=9) and Elderly (n=9) Subjects at 6 and 21C

0 20 40 60 80

% VO2 max

12

14

16

18

20

22

24

26

28

30

32

Tem

pe

ratu

re o

C

Y Tf 6oC

Y Tf 21oC

E Tf 21oC

E Tf 6oC

(3) What is ‘Excess Winter Mortality’?

Excess Winter Mortality

• EWM is the number of deaths occurring between 1st December and 31st March less the number of deaths in the rest of the year

• Since 1841 there have been approximately 3 million avoidable deaths in the older population in the winter

• For every 1◦C reduction in the average ambient temperature in the winter, there are 8,000 more deaths (Curwen M 1997)

Ratio

of o

bser

ved

to e

xpec

ted

deat

hs

Maximum daily temperature C0 10 20 30

.75

1

1.25

1.5

Gradient represents

strength of low temperature-

mortality relationship

Frequency distribution of max. temperatures

Mortality and temperature distribution

Excess Winter Deaths

LONDON, 1986-96

D

AIL

Y D

EA

TH

S

01jan1986 01jan1988 01jan1990 01jan1992 01jan1994 01jan1996

0

100

200

300

400

Inside vs Outside Cold

• Few older people live in homes without central heating but many restrict their use of it mainly on grounds of cost (fuel poverty)

• Moving from a cold home to outside cold carriessignificantly more risk to health than moving from a warm home

• Relatively minor cold exposures in daily life are sufficient to induce significant hypertension and haemoconcentration

• Linear inverse relationship between activitylevels and indoor cold with increased outdoorexcursions in older people living in cold homes

Inside ColdR

ela

tive r

isk o

f d

eath

Date1Jan 1Apr 1Jul 1Oct 31Dec

.8

1

1.2

1.4

1.6 Coldest 25% of homes

Warmest 25% of homes

Euro-winter Study

Notable Findings• Percentage increases in all cause mortality per 1C (below

18C) are greater in warm than in cold regions (eg Athens vs south Finland)

• High indices of cold related mortality are associated with– high mean winter temperatures– low living room temperatures– limited bedroom heating– low clothing protection– physical activity

• Lag effects exist between onset of cold and death

(4) What are its causes?

Causes of Winter Death

• Less than 1% due to hypothermia

• Small number of deaths due to influenza, except in epidemic years (eg winter ‘89/90)

• Respiratory illness (eg COPD, bronchitis) 12 day’ lag effect’; deaths declining due to warmer homes

• Thrombotic illness (eg MI, stroke) 3-7 day ‘lag effect’; deaths show little change over time and are related to outdoor cold exposure

(5) Can we do anything about it?

Aderdeen,Scotland

0-8°C in JanuaryYakutsk ,Siberia

-26.6°C

All cause mortality unaffected

Kuwait

8-18°C in January

50 Year Regression DataExcess Winter Mortality 1950 - 2010

0

20,000

40,000

60,000

80,000

100,000

120,000

1950

/195

119

52/195

319

54/195

519

56/195

719

58/195

919

60/196

119

62/196

319

64/196

519

66/196

719

68/196

919

70/197

119

72/197

319

74/197

519

76/197

719

78/197

919

80/198

119

82/198

319

84/198

519

86/198

719

88/198

919

90/199

119

92/199

319

94/199

519

96/199

719

98/199

920

00/200

120

02/200

320

04/200

520

06/200

720

08/200

9

Summary of the Evidence - Cold

• Extremes of cold incur high rates of morbidity and mortality in older people via respiratory and thrombotic illness• Respiratory mortality appears to be falling due to warmer homes •Indoor and outdoor cold are independent risk factors• Predisposing factors appear to be:

– age (frailty, co-morbidity)– home conditions– high-risk behaviour – social isolation– limited access to health and social care– social inequality

Public Health Advice

“We will not be bullied into good health by the likes of Mr Chadwick”

The London Times, 1848