The new environmental health SIR, - Dr John Ashton's editorial gives an excellent picture of the modern approach to public health.' His list of topics with which it is concernedhousing, sanitation, education, transport, etc illustrates the fields into which health now has an input. But it is also worth while to emphasise the other side of the coin and point out that the professions concerned-architecture, town planning, education, engineering, and agriculture -also have an important input into health. One exemplary multidisciplinary field that needs the cooperation of health professionals with many of these other professionals is accident prevention. This is, by a long way, the most important public health problem affecting children, adolescents, and young adults. It is therefore somewhat ironic that in the same issue of the BMJ there is a note on the establishment of a Trauma Foundation, whose resources will be devoted to research, postgraduate education, and providing hospital facilities for injured people.2 Regrettably, no mention is made of resources devoted to the prevention of such accidents. The irony is further heightened by the accompanying illustration of a cyclist who seems to have a head injury after being struck by a car-but no cycle helmet is in evidence. We urge that all such initiatives, in the spirit of the orientation described by Dr Ashton, recognise fully the proportions of the problem of injuries resulting from accidents, especially as it affects young people. R H JACKSON I B PLESS
Child Accident Prevention Trust, London WIN 4DE 1 Ashton J. Sanitarian becomes ecologist: the new environmental health. BM7 1991;302:189-90. (26 January.) 2 Walker A. Charity for trauma victims. BMJ7 1991;302:200.
(26 January.)
Is housing a public health issue? SIR,-We share the view of Dr Paul Roderick and colleagues that public health doctors should reassess their role in housing issues.' In 1989 we studied 27 consecutive applications for medical priority for rehousing within Wakefield metropolitan district. Applications were scored by the housing department and by two doctors who routinely undertook such work. Applications were rated urgent, fairly urgent, non-urgent, or other action, in accordance with normal practice. Each scorer was blind to the other ratings. The priorities allocated are shown in the table. Normally about half of applications are rated non-urgent, 40% fairly urgent, and 10% urgent, so the results suggested an altered scoring habit by Dr B. In eight cases all three assessors agreed and in 13 two agreed. In six cases none agreed: this included four marked "other action" by the housing department, of which three were suitable for aids and adaptations to their existing home and one required further medical advice. Dr A agreed with Dr B in 10 of the 27 cases. Excluding the four marked other action, Dr A agreed with the housing department in 17 of 23 and Dr B agreed with the housing department in 10 of 23. Because of these results rehousing procedures were revised across Wakefield metropolitan disRating of 27 consecutive applications for rehousing Source of ratings
Housing department DrA DrB
528
Other Non- Fairly urgent urgent Urgent action 12 19 11
8 7 5
3 1 11
trict (covering Pontefract and Wakefield health districts). A common pathway was established for rehousing requests and for aids and adaptations to existing accommodation. The housing department took over routine priority setting of applications. For most elderly, frail applicants it is the degree of handicap within the home and the prospects for amelioration in different housing that determine priority; the medical opinion adds little. The medical sessions were reallocated to other desirable community interventions. Time was freed, however, for more detailed medical consideration of less common cases, such as young people with disabilities and patients with unusual malignancies or HIV disease, in which determining the prognosis or scope for benefit requires a medical input. Housing remains an important health issue, especially in a district like Wakefield with a high proportion of council housing. Medical assessment for rehousing may redistribute the problem but does not contribute to a solution. G C SUTTON R MUTHUKUMAR
Pontefract Health Authority, Pontefract WF7 6HT 1 Roderick P, Victor C, Connelly J. Is housing a public health issue? A survey of directors of public health. BMJ 1991;302: 157-60. (19 January.)
Prospective or retrospective: what's in a name? SIR,-I sympathise with Professor Jan P Vandenbrouke in his desire to abandon the use of the words prospective and retrospective in the description of clinical and epidemiological research and have no quarrel with his recommendation that they should be abandoned.' In describing epidemiological studies they can commonly be replaced by the less ambiguous but clumsier terms "cohort" and "case-control." Whether Professor Vandenbrouke is right in suggesting that the use of prospective and retrospective in the sense we now give to cohort and case-control as a description of epidemiological studies derived from a school "originally centred on epidemiologists at Johns Hopkins" I don't know; but I do know that in this country they were originated by Sir Austin Bradford Hill when he and I came to write our 1954 paper on the mortality of doctors in relation to their smoking habits.2 We wrote then in relation to the previous case-control studies ofthe aetiology oflung cancer that "Further retrospective studies of the same kind would seem unlikely to advance our knowledge materially.... If there were any undetected flaw in the evidence that such studies have produced, it would be exposed only by some entirely new approach. That approach we considered should be 'prospective'*." We then gave as a footnote "*QED. Characterized by looking forward into the future (Leigh Hunt: 'He was a retrospective rather than a prospective man')." Since the Harvard School3 began to use the terms in a different sense it has probably become sensible to abandon them altogether, but unless there exists some earlier reference their use in the sense we gave them in 1954 should be attributed to Sir Austin Bradford Hill. RICHARD DOLL
ICRF Cancer Studies Unit, Oxford OX2 6HE 1 Vandenbrouke JP. Prospective or retrospective: what's in a name? BMJ 1991;302:249-50. (2 February.) 2 Doll R, Hill AB. The mortality of doctors in relation to their smoking habit?L a preliminary report. BMJ 1954;i: 1451-5. 3 MacMahon B, Pugh TF. Epidemiology: principles and methods. Boston: Little, Brown, 1970:43-4.
4
SIR,-As Professor Jan P Vandenbroucke states, the words retrospective and prospective should
be used precisely or not at all when describing research designs.' Those of us who argued over the wording of definitions in the Dictionary of Epidemiology devoted much time and effort to these two words.2 We agreed that at least among epidemiologists their usage ought to be as we described: retrospective study is a synonym for case-control study, prospective study is a synonym for cohort study. We recognised that medical scientists in other specialties might be less careful in choosing how to describe what they had done. We hoped that medical journal editors would keep a copy of this dictionary in their offices and use it if in doubt. Like Professor Vandenbroucke, I have observed frequent inconsistencies, especially in the use of "prospective." I hope this admonition will be heeded by authors and by editorial staff of medical journals. JOHN M LAST
University of Ottawa,
Ottawa,lCanada KIH 8M5 1 Vandenbroucke JP. Prospective or retrospective: what's in a name? BMJ 1991;302:249-50. (2 February.) 2 Last JM, ed. A dictionary of epidemiology. 2nd ed. New York: Oxford University Press, 1987.
SIR,-Dr Jan P Vandenbroucke's suggestion simply to abandon the use of "prospective" and "retrospective" in clinical research is a provocative solution to an important source of confusion.' However, the eradication of these two terms seems neither realistic nor desirable: not realistic because in practice these words are firmly rooted in clinicians' vocabulary and will not be susbstituted by paraphrases; not desirable because a clarification is needed between clinicians and epidemiologists about what they mean by prospective and retrospective. Clinicians usually designate as retrospective a study for which they retrieve historical data recorded before the study began and prospective a study for which they collect concurrent data. Epidemiologists call a study prospective when the suspected cause is measured before the outcome occurs. Conversely, a retrospective study (without other specification) means that the outcome has already occurred at the time the suspected cause is measured. In addition, these two types of study require the presence of a comparison group. Retrospective study is synonymous with casecontrol study. The corresponding synonym for prospective study would be "exposed-nonexposed" study, but the usual term is follow up or cohort study. Whether the analysis relies' on historical or concurrent data recording and whether it is a primary or secondary analysis are important qualifications for the interpretation of the results, but these factors do not constitute specific study categories. For example, both prospective and retrospective studies can use past or present
information. Two simple rules may help. Firstly, the expressions prospective study and retrospective study without other details of the study design should be used exclusively in their epidemiological definitions, prospective study being synonymous with follow up study and retrospective study with casecontrol study. Secondly, if the research is not a case-control or a follow up study, prospective and retrospective may be used only if the study design is explicitly mentioned. For example, a prospective case series would define a study based on information systematically obtained from a series of new cases, without a comparison group, over a given time; in contrast, a retrospective case series would describe a similar design, but with information retrieved from past records. These expressions are a blend of clinicians' and epidemiologists' vocabulary, and they can be understood by both. They have the advantage of being shorter than descriptions and thus easier to adopt.
BMJ
VOLUME 302
2 MARCH 1991
Child Accident Prevention Trust, London WIN 4DE 1 Ashton J. Sanitarian becomes ecologist: the new environmental health. BM7 1991;302:189-90. (26 January.) 2 Walker A. Charity for trauma victims. BMJ7 1991;302:200.
(26 January.)
Is housing a public health issue? SIR,-We share the view of Dr Paul Roderick and colleagues that public health doctors should reassess their role in housing issues.' In 1989 we studied 27 consecutive applications for medical priority for rehousing within Wakefield metropolitan district. Applications were scored by the housing department and by two doctors who routinely undertook such work. Applications were rated urgent, fairly urgent, non-urgent, or other action, in accordance with normal practice. Each scorer was blind to the other ratings. The priorities allocated are shown in the table. Normally about half of applications are rated non-urgent, 40% fairly urgent, and 10% urgent, so the results suggested an altered scoring habit by Dr B. In eight cases all three assessors agreed and in 13 two agreed. In six cases none agreed: this included four marked "other action" by the housing department, of which three were suitable for aids and adaptations to their existing home and one required further medical advice. Dr A agreed with Dr B in 10 of the 27 cases. Excluding the four marked other action, Dr A agreed with the housing department in 17 of 23 and Dr B agreed with the housing department in 10 of 23. Because of these results rehousing procedures were revised across Wakefield metropolitan disRating of 27 consecutive applications for rehousing Source of ratings
Housing department DrA DrB
528
Other Non- Fairly urgent urgent Urgent action 12 19 11
8 7 5
3 1 11
trict (covering Pontefract and Wakefield health districts). A common pathway was established for rehousing requests and for aids and adaptations to existing accommodation. The housing department took over routine priority setting of applications. For most elderly, frail applicants it is the degree of handicap within the home and the prospects for amelioration in different housing that determine priority; the medical opinion adds little. The medical sessions were reallocated to other desirable community interventions. Time was freed, however, for more detailed medical consideration of less common cases, such as young people with disabilities and patients with unusual malignancies or HIV disease, in which determining the prognosis or scope for benefit requires a medical input. Housing remains an important health issue, especially in a district like Wakefield with a high proportion of council housing. Medical assessment for rehousing may redistribute the problem but does not contribute to a solution. G C SUTTON R MUTHUKUMAR
Pontefract Health Authority, Pontefract WF7 6HT 1 Roderick P, Victor C, Connelly J. Is housing a public health issue? A survey of directors of public health. BMJ 1991;302: 157-60. (19 January.)
Prospective or retrospective: what's in a name? SIR,-I sympathise with Professor Jan P Vandenbrouke in his desire to abandon the use of the words prospective and retrospective in the description of clinical and epidemiological research and have no quarrel with his recommendation that they should be abandoned.' In describing epidemiological studies they can commonly be replaced by the less ambiguous but clumsier terms "cohort" and "case-control." Whether Professor Vandenbrouke is right in suggesting that the use of prospective and retrospective in the sense we now give to cohort and case-control as a description of epidemiological studies derived from a school "originally centred on epidemiologists at Johns Hopkins" I don't know; but I do know that in this country they were originated by Sir Austin Bradford Hill when he and I came to write our 1954 paper on the mortality of doctors in relation to their smoking habits.2 We wrote then in relation to the previous case-control studies ofthe aetiology oflung cancer that "Further retrospective studies of the same kind would seem unlikely to advance our knowledge materially.... If there were any undetected flaw in the evidence that such studies have produced, it would be exposed only by some entirely new approach. That approach we considered should be 'prospective'*." We then gave as a footnote "*QED. Characterized by looking forward into the future (Leigh Hunt: 'He was a retrospective rather than a prospective man')." Since the Harvard School3 began to use the terms in a different sense it has probably become sensible to abandon them altogether, but unless there exists some earlier reference their use in the sense we gave them in 1954 should be attributed to Sir Austin Bradford Hill. RICHARD DOLL
ICRF Cancer Studies Unit, Oxford OX2 6HE 1 Vandenbrouke JP. Prospective or retrospective: what's in a name? BMJ 1991;302:249-50. (2 February.) 2 Doll R, Hill AB. The mortality of doctors in relation to their smoking habit?L a preliminary report. BMJ 1954;i: 1451-5. 3 MacMahon B, Pugh TF. Epidemiology: principles and methods. Boston: Little, Brown, 1970:43-4.
4
SIR,-As Professor Jan P Vandenbroucke states, the words retrospective and prospective should
be used precisely or not at all when describing research designs.' Those of us who argued over the wording of definitions in the Dictionary of Epidemiology devoted much time and effort to these two words.2 We agreed that at least among epidemiologists their usage ought to be as we described: retrospective study is a synonym for case-control study, prospective study is a synonym for cohort study. We recognised that medical scientists in other specialties might be less careful in choosing how to describe what they had done. We hoped that medical journal editors would keep a copy of this dictionary in their offices and use it if in doubt. Like Professor Vandenbroucke, I have observed frequent inconsistencies, especially in the use of "prospective." I hope this admonition will be heeded by authors and by editorial staff of medical journals. JOHN M LAST
University of Ottawa,
Ottawa,lCanada KIH 8M5 1 Vandenbroucke JP. Prospective or retrospective: what's in a name? BMJ 1991;302:249-50. (2 February.) 2 Last JM, ed. A dictionary of epidemiology. 2nd ed. New York: Oxford University Press, 1987.
SIR,-Dr Jan P Vandenbroucke's suggestion simply to abandon the use of "prospective" and "retrospective" in clinical research is a provocative solution to an important source of confusion.' However, the eradication of these two terms seems neither realistic nor desirable: not realistic because in practice these words are firmly rooted in clinicians' vocabulary and will not be susbstituted by paraphrases; not desirable because a clarification is needed between clinicians and epidemiologists about what they mean by prospective and retrospective. Clinicians usually designate as retrospective a study for which they retrieve historical data recorded before the study began and prospective a study for which they collect concurrent data. Epidemiologists call a study prospective when the suspected cause is measured before the outcome occurs. Conversely, a retrospective study (without other specification) means that the outcome has already occurred at the time the suspected cause is measured. In addition, these two types of study require the presence of a comparison group. Retrospective study is synonymous with casecontrol study. The corresponding synonym for prospective study would be "exposed-nonexposed" study, but the usual term is follow up or cohort study. Whether the analysis relies' on historical or concurrent data recording and whether it is a primary or secondary analysis are important qualifications for the interpretation of the results, but these factors do not constitute specific study categories. For example, both prospective and retrospective studies can use past or present
information. Two simple rules may help. Firstly, the expressions prospective study and retrospective study without other details of the study design should be used exclusively in their epidemiological definitions, prospective study being synonymous with follow up study and retrospective study with casecontrol study. Secondly, if the research is not a case-control or a follow up study, prospective and retrospective may be used only if the study design is explicitly mentioned. For example, a prospective case series would define a study based on information systematically obtained from a series of new cases, without a comparison group, over a given time; in contrast, a retrospective case series would describe a similar design, but with information retrieved from past records. These expressions are a blend of clinicians' and epidemiologists' vocabulary, and they can be understood by both. They have the advantage of being shorter than descriptions and thus easier to adopt.
BMJ
VOLUME 302
2 MARCH 1991
