Some Remarks on Contemporary British Medical StatisticsAuthor(s): E. D. AchesonSource: Journal of the Royal Statistical Society. Series A (General), Vol. 131, No. 1 (1968), pp.9-12Published by: Wiley for the Royal Statistical SocietyStable URL: http://www.jstor.org/stable/2344081 .

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1968] 9

Social and Medical Statistics

Some Remarks on Contemporary British Medical Statistics

By E. D. ACHESON Oxford Record Linkage Study, Nuffield Department of Clinical Medicine,

University of Oxford

THE year in which the Journal of this learned Society was first published, 1838, was also the year for which statistics of a medical nature were first published on a national scale by a government department-I refer of course to the first report on mortality published by the Registrar General. It would be difficult to exaggerate the influence of the regular annual analyses of the three events, birth, death, and marriage, which have appeared over the succeeding 130 years. The death tabulations, with which medical men are most familiar, have been invaluable, providing almost the only data about the long-term fluctuations in the frequency of the more brief and fatal diseases, assisting in the formulating of hypotheses, and influencing and compelling public health legislation. In their current fully developed form, together with the decennial supplements, they are, I believe, unsurpassed in any country.

But times have changed. Table 1, in which material taken from William Farr's report of 1838 is compared with that from a recent year, provides a glimpse of the problems of a different age. At that time one-sixth of all deaths in England and Wales were ascribed to five diseases: typhus, scarlet fever, smallpox, measles, and whooping cough: if tuberculosis were added the figure became one-third. The brevity of the dominant diseases was such, their concentration in space and time was such, that one doctor could observe and one piece of paper report not only the circumstances of death but the circumstances of exposure to the causative factor. My theme this evening will be to examine whether British official medical statistics have changed with the times.

Of all the changes which have occurred since our current system of national medical statistics was developed, there are, I think, four which are particularly relevant to this topic. These are, first, the radical difference between now and then in the time scale of evolution of the dominant diseases; in bronchitis, coronary disease, many cancers, and peptic ulcer we are concerned with years or decades, not days or weeks; second, the increased appreciation of the importance of familial factors in health and disease, and here I refer not only to genetics but to the family in the sociological sense; third, the increased complexity of the organization of medicine and of the preventive and therapeutic measures which can be taken; and fourth, the increase in population movement.

These trends are large and are likely to continue. They bring with them important new needs. I have selected four of these. The first need is for data about the incidence of illness which is neither rapidly fatal nor the subject of statutory notification. In England the first official attempt to meet this need came with the setting up of the Hospital Inpatient Enquiry in 1949 (MacKay, 1951). This obtains, on a country-wide scale, basic data about every tenth discharge from hospital. Many criticisms can be levelled at this Enquiry. As the abstracts are not identified it is impossible to

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10 ACHESON-Medical Statistics [Part 1,

distinguish between a person discharged and readmitted several times in a year and several different persons discharged once. This inflates morbidity rates, reduces fatality rates, and biases in an unpredictable manner distributions of duration of stay. There is a further important deficiency. As the sample is of discharges and not persons, it is impossible to follow or even to define cohorts of persons for longitudinal study.

The Hospital Activity Analysis which is to replace the Enquiry calls for abstraction of data concerning 100 per cent of the hospital inpatient spells of treatment (Benjamin, 1965). Unfortunately, it has many of the deficiencies of its predecessor. The identi- fication data recorded will be meaningless outside the individual hospital and it will be impossible, therefore, to collate the material with the subsequent or previous experience of the person concerned.

This leads me on to the second need, which is the facility to follow samples of persons in spite of movement through the country; for example, to collate information about the successive hospital admissions of a person with data about his subsequent death; or to collate information about exposure to occupational hazards or drugs with information about subsequent illnesses. It is not generally recognized to what extent medical statistical research is impeded by the difficulties in obtaining the most elementary follow-up data.

But there is a further need under this heading-the need for an entirely new type of statistical table; new, that is, in the sense that it would be published regularly on a national scale. For want of a better term I shall call these "personal longitudinal statistics"; by this term I mean statistics in which the unit is the person, not the event, and which involve the correlation of two or more events separated in time. I envisage, for example, the regular publication of survival rates, re-operation rates, re-admission rates, which are not limited to the experience of patients within a particular hospital but trace their course wherever they are re-admitted or wherever they should die in a defined period of time: the publication also of rates of return to work according to condition and type of treatment; also classifications of persons in terms of the total costs they have attracted in a period of time not only within the health service, but within the wider context of the whole welfare service.

The statistical needs that I have discussed, and the need for regular information about families which I have no time to discuss, require a fundamental change in the organization of the material used in British medical statistics. In a nutshell, the change must be from the statistics of events (whether the event be a birth, death, admission, attendance or a claim for benefit) to the statistics of persons and of families.

Ideas, like diseases, have latent periods during which they appear to lie dormant. The first explicit statement I have found of the advantages of "personal longitudinal statistics" is in the Report of the Committee on the Preparation of Army Medical Statistics published in 1861 of which Farr was the principal author. We have it again in the Dawson Report of 1920 and from Dr Percy Stocks in 1944. The term "record linkage" was coined 21 years ago by H. L. Dunn, the American demographer, to denote the bringing together of birth, marriage and death records in a series of personal cumulative files. The idea of a national file of families as an effective means of studying fertility over the complete reproductive cycle was proposed by the Statistics Committee of the Royal Commission on Population-a committee which included members of this Society. None of these ideas has been turned into practice, principally because the technical means have only recently become available.

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1968] AcHEsoN-Medical Statistics 11

This year record linkage has come of age. Three international scientific gatherings have discussed this topic in as many months. The Medical Research Council (1967) has published an official endorsement of the notion of a national system of medical record linkage involving the assembly of the vital records and hospital inpatient data into a series of personal cumulative files. Further, it has stated that such a system could be founded on existing practices and has expressed the view that "the advantages of such a scheme are so manifold as to outweigh the difficulties of its implementation".

What then are the difficulties? Most people working in this field would agree that neither the lack of equipment nor of techniques are any longer critical. Nor, in my view, is the basic difficulty one of expense. The largest item of cost, that of data preparation, is already met (or shortly will be) as the data preparation for a useful first-stage system (i.e. on the scale indicated above) is already provided for on a national basis in connection with the Hospital Activity Analysis and the registration of vital events.

The real difficulty is a political one and is a result of a fundamental aspect of record linkage. Record linkage is concerned with bringing together data about persons across departmental boundaries. It is interested in the whole cake, not the departmental slice. As Bothwell has said, "the person is the unit not the branch of the health service"; nor, I would add, is the Health Service itself necessarily the unit; we may wish to accumulate with health data information about welfare and education. Unfortunately, the departments and authorities concerned with health matters con- sider it no part of their business to modify their procedures to assist the collation of data with those of another department; each sees fit to take a departmental view, which in the nature of the problem means a defensive negative view against change even when this may be in the general interest.

Although opinion in different countries varies on this point, in Britain we may feel it prudent to limit what data we collate with those bearing on medical matters. Perhaps information about judicial and tax matters should be accumulated separately. For my own part I hope to see a single system of personal information from which statistics could be derived embracing the closely related topics of health, sickness, education, and welfare, regularly enriched by data collected in the field on population samples.

In practice, the most important single prerequisite is the adoption of one personal filing number by all those concerned. At the moment, alas, the departmental barri- cades are up and the trenches are manned. Someone must reconcile their views-or, to put it less politely, knock their heads together in the general interest! Undoubtedly such changes will need capital expenditure; but, as in the case of the standardization of the railway gauges between the states of Australia, not to spend this money may be a false economy. Recently, the United States armed services and the hospital system of the Veterans' Administration have sacrificed their own filing and identity numbers and adopted the social security number for all personal records.

I have a final point to make. There is a view that a system of linked medical records must await the millennium when each hospital and clinic has its computer installation, and data flicker from a thousand terminals "on line". This is not true. The objectives that have been discussed this evening can be met in stages, and the first stage, the planning for a cumulative national index of hospital morbidity and mortality data on a quarterly batch-processing basis, could begin without delay. To have such an index in two sequences-by name and by diagnosis, carrying simply date, hospital file reference, and elementary social data-would be a considerable

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12 AcBEsoN-Medical Statistics [Part 1,

advance and the same material could be used to provide some unique statistical tables. In Scotland, plans are in motion for such a system.

To conclude, British official medical statistics have not changed with the times and are still based on a system devised 130 years ago. Two fundamental changes are needed; first, the unit of study should be altered from the event to the person and family; second, the scope should be enlarged to embrace not only medicine but education and possibly welfare as well.

TABLE 1 Numbers of deaths from selected causes in 1838 (England) and 1963

(England and Wales)

Cause of death 1838 1963

Fever Typhus . 24,577 37 Scarletina J Smallpox 16,268 Measles 6,514 127 Whooping cough 9,107 36 Consumption 59,025 5,026

All the above 115,491 5,226 All causes 342,529 572,868

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(Reprinted 1950.) DuNN, H. L. (1946). Record linkage. Amer. J. Publ. Health, 36, 1412. FARR, W. (1861). In Report on Army Medical Statistics (by Lord Herbert, Sir A. Tulloch and

Dr Farr). (Parliamentary Paper No. 366.) MACKAY, D. (1951). General Register Office Studies on Medical and Population Subjects. No. 4:

Hospital Morbidity Statistics. London: H.M.S.O. REGISTRAR GENERAL (1839). Annual Report of the Registrar General of Births, Deaths and

Marriages. London. (1965). Registrar General's Statistical Review of England and Wales for 1963. Part L

London: H.M.S.O. RoYAL COMMISSION ON POPULATION (1950). Papers. Vol. II: Reports and Selected Papers of the

Statistics Committee. London: H.M.S.O. STOCKS, P. (1944). Measurement of morbidity. Proc. Roy. Soc. Med., 37, 593.

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