eliminating the "high tail" but share his concern that this may be difficult to achieve. Though normal distributions of physiological and behavioural variables have been moved to the left or right, we are unaware of an intervention that has altered the shape of a distribution. Before a population strategy is adopted the costs and benefits must be weighed. Consideration should be given to the evidence that light drinkers (1-15 units a week) have a lower mortality than abstainers and occasional drinkers and that this is not entirely due to sick people stopping drinking.: Therefore the possibility of a population strategy causing harm by pushing light drinkers up the left hand side of the U shaped curve must be considered. A prospective trial might establish the value of a population strategy, but, given the difficulties of evaluating studies of dietary advice, the verdict would probably be "not proven." So apart from deploring the current lack of evidence what should the pragmatist do? We think that the association between light drinking and reduced mortality should be regarded as causal. Strategies to reduce alcohol consumption should be examined, perhaps by mathematical modelling, and only those whose benefits outweigh the costs should be adopted. For the present we agree with Michael Marmot and Eric Brunner that it would be inappropriate to urge people to drink more.' None the less, to introduce a population strategy without further analysis risks a humiliating change of policy at some future date with a subsequent loss of public confidence in advice on public health. MICHAEL R BRADDICK
Highland Health Board, Hilton Hospital, Inverness IV2 3PH CHRISTOPHER A BIRT
Highland Health Board, Royal Northern Infirmary, Inverness IV3 5SF 1 Anderson P. Alcohol as a key area. BMJ 1991;303:766-9.
(28 September.) 2 Shaper AG, Wannamathee G, Walker M. Alcohol and mortality in British men: explaining the U shaped curve. Lancet 1988;ii: 1267-73. 3 Marmot M, Brunner E. Alcohol and cardiovascular disease: the status of the U shaped curve. B,J 1991;303:565-8.
(7 September.)
Strategies for preventing osteoporosis SIR, -M R Law and colleagues discuss the role of calcium supplements in preventing osteoporosis,' as others have done.24 Though this debate continues, it is clear that dietary deficiency of calcium is a risk factor for osteoporosis. To assess general practitioners' knowledge of calcium requirements and sources of calcium in the diet 53 principals attending a seminar on the menopause completed a questionnaire. The overall knowledge was low, and many commented that they had received no information on calcium in the diet; the commonest response to each question was "don't know" (range eight to 23 responses). In addition, 13 of the doctors underestimated the recommended daily intake of calcium for children (600 mg) and during the third trimester of pregnancy (1200 mg) and 21 overestimated the percentage absorption of calcium (20-40%). Dairy products account for over half of dietary calcium-a quarter of the general practitioners underestimated the role of dairy products (and a fifth didn't know). Only eight knew that skimmed milk contains more calcium than full cream milk, and 48 underestimated milk's calcium content (700 mg per pint). This questionnaire clearly showed that while the debate on the role of calcium supplements continues, information about the sources of dietary calcium, various recommended daily allowances,
1060
and the importance of dairy products is clearly needed. The average intake of milk has fallen by a fifth over the past 10 years, partly in response to "medical pressures" to reduce fat intake. Unfortunately, the messages that milk is the main source of dietary calcium and that the calcium is in the milk rather than the cream have not been emphasised, and many people in the commnunity may now have diets potentially deficient in calcium. D CLEMENTS K HARDING Department of Postgraduate Studies, University Hospital of Wales, Cardiff CF4 4XW
1 Law MR, Wald NJ, Meade TW. Strategies for prevention of osteoporosis and hip fracture. BMJ7 1991;303:453-9. (24 August.) 2 Kanis JA, Passmore R. Calcium supplementation of the diet. BMJ7 1989;298:137-40, 205-8. 3 Nordin BEC, Heaney RP. Calcium supplementation of the diet: justified by present evidence. BMJ 1990;300:1056-60. 4 Misra R, Anderson DC. Providing the fetus with calcium. BMJ 1990;300: 1220-1.
Action plan for preventing coronary heart disease SIR, -We believe that the action plan for preventing coronary heart disease based on assessment of multiple risk, proposed by a working group of the Coronary Prevention Group and British Heart Foundation, merits further discussion.' Carrying out the action plan is easier said than done. The practical example assumes that a practice with five doctors and two nurses will allocate a nurse to 10 health promotion clinics a week-in other words, a full time job. The experience of OXCHECK2 and the family heart study (unpublished data) confirms that the nurse needs to spend at least 45 minutes with each person who attends for a health check if high quality intervention is the aim. The action plan allows only 20 minutes per appointment, which is insufficient to establish the health needs of a person and offer tailored advice. Even with a full time nurse offering only 20 minute appointments, after 3000 health checks required by the general practice contract have been done only 1500 follow up appointments are left. The working group expects each practice to have 1000 "clinical risk patients," or 333 each year for three years, and simply to record a mean of three cholesterol or blood pressure readings for each of these would require another 1000 appointments a year. This leaves 500 appointments for following up the multiple risk group-that is, one appointment for 500 of the 3000 screened, two appointments for 250 of the 3000, or three appointments for only 125 of the 3000. During this screening and follow up programme, of course, the nurse has been removed from other duties, so the practice's usual treatment room services are halved. The cost of this screening and follow up can be measured in dressings not done, opportunities for family planning missed, diabetes and asthma clinics curtailed, and all the other clinical practices in which the nurse would otherwise be engaged. If coronary heart disease can be reduced by this type of health promotion clinic-and the answer to that question is still not clear-a huge commitment in nursing and administrative time is needed. This must come either from present resources, in which case our disease treatment service must be reduced, or from new investment in primary care. Unless this is forthcoming, coronary heart disease prevention clinics will touch only the tip of the iceberg. ANN-LOUISE KINMONTH GERAINT DAVIES Faculty of Medicine, Aldermoor Health Centre, Southampton SO I 6ST
1 Working Group of the Coronary Prevention Group and the British Heart Foundation. An action plan for preventing coronary heart disease in primary care. BMJ 1991;303:748-50. (28 September.) 2 Imperial Cancer Research Fund OXCHECK Study Group. Prevalence of risk factors for heart disease in OXCHECK trial: implications for screening in primary care. BM 1991;302: 1057-60. (4 May.)
Coronary risk-disk SIR,-Hugh Tunstall-Pedoe proposes that the acid test of his coronary risk-disk should be its usefulness.' It is certainly impressive that good predictions are obtained in a population different from the parent population, but it is in the application to individuals that we are concerned. One of us (GHH) estimated his five year absolute risk of coronary event as' 18% with the logistic formula. This compares with a 13% risk if he was normotensive, had a normal cholesterol concentration, and had never smoked. The 5% reduction attainable by changing his lifestyle implies that 20 people like him will have to change their habitsassuming this is effective-to save one coronary event. Would he be the lucky one? Moreover, the high standard error of the coefficient of the group of ex-smokers provides a range for his risk of 12-26%. This uncertainty suggests that it may be better to use the equation; an ordinary pocket scientific calculator with a memory and logarithmic functions will give the result in less than 30 seconds-it is cheaper than a risk disk and more versatile. Actually doing the calculations reminds one ofthe basis of interpreting risk-a regression equation with the problems of interdependence between variables which are usually ignored but may be very important. The main use of the risk disk would be in targeting health promotion on those most in need. We believe that a statement of absolute risk is far more likely to be effective than identifying the tenth of the population in which the patient belongs, particularly if the middle tenths are to be ignored in favour of the top 20%, who are likely to suffer 40% of coronary events. There is the potential for promoting a false sense of security, which would not occur with the absolute risk, as in the example ofWTH, whose risk is still 2% despite him being in one of the lower tenths. The test of usefulness must be a measure of the effect of using the disk on coronary morbidity and mortality over five years. Perhaps it is premature to engage in fortune telling until we have the result of such a study. G H HALL Exeter EX2 4NT W T HAMILTON Exeter EXI 1 SR I Tunstall-Pedoe H. The Dundee coronary risk-disk for management of change in risk factors. BMJ 1991;303:744-7. (28
September.)
Imported HIV infection acquired heterosexually SIR,-In view of the increasing workload at our clinic and nationally resulting from HIV infection acquired heterosexually we reviewed the epidemiological data on our female patients infected with HIV. To date 75 women infected with HIV have been under the care of the departments of genitourinary medicine of St Mary's Hospital and Central Middlesex Hospitals in central London. Four of these patients have had an AIDS defining illness. The table shows the risk factors for acquisition of HIV infection among these patients. Forty of the women acquired their infections abroad through heterosexual intercourse. Of these 40, 34 were African nationals who had recently
BMJ VOLUME 303
26 OCTOBER 1991
Highland Health Board, Hilton Hospital, Inverness IV2 3PH CHRISTOPHER A BIRT
Highland Health Board, Royal Northern Infirmary, Inverness IV3 5SF 1 Anderson P. Alcohol as a key area. BMJ 1991;303:766-9.
(28 September.) 2 Shaper AG, Wannamathee G, Walker M. Alcohol and mortality in British men: explaining the U shaped curve. Lancet 1988;ii: 1267-73. 3 Marmot M, Brunner E. Alcohol and cardiovascular disease: the status of the U shaped curve. B,J 1991;303:565-8.
(7 September.)
Strategies for preventing osteoporosis SIR, -M R Law and colleagues discuss the role of calcium supplements in preventing osteoporosis,' as others have done.24 Though this debate continues, it is clear that dietary deficiency of calcium is a risk factor for osteoporosis. To assess general practitioners' knowledge of calcium requirements and sources of calcium in the diet 53 principals attending a seminar on the menopause completed a questionnaire. The overall knowledge was low, and many commented that they had received no information on calcium in the diet; the commonest response to each question was "don't know" (range eight to 23 responses). In addition, 13 of the doctors underestimated the recommended daily intake of calcium for children (600 mg) and during the third trimester of pregnancy (1200 mg) and 21 overestimated the percentage absorption of calcium (20-40%). Dairy products account for over half of dietary calcium-a quarter of the general practitioners underestimated the role of dairy products (and a fifth didn't know). Only eight knew that skimmed milk contains more calcium than full cream milk, and 48 underestimated milk's calcium content (700 mg per pint). This questionnaire clearly showed that while the debate on the role of calcium supplements continues, information about the sources of dietary calcium, various recommended daily allowances,
1060
and the importance of dairy products is clearly needed. The average intake of milk has fallen by a fifth over the past 10 years, partly in response to "medical pressures" to reduce fat intake. Unfortunately, the messages that milk is the main source of dietary calcium and that the calcium is in the milk rather than the cream have not been emphasised, and many people in the commnunity may now have diets potentially deficient in calcium. D CLEMENTS K HARDING Department of Postgraduate Studies, University Hospital of Wales, Cardiff CF4 4XW
1 Law MR, Wald NJ, Meade TW. Strategies for prevention of osteoporosis and hip fracture. BMJ7 1991;303:453-9. (24 August.) 2 Kanis JA, Passmore R. Calcium supplementation of the diet. BMJ7 1989;298:137-40, 205-8. 3 Nordin BEC, Heaney RP. Calcium supplementation of the diet: justified by present evidence. BMJ 1990;300:1056-60. 4 Misra R, Anderson DC. Providing the fetus with calcium. BMJ 1990;300: 1220-1.
Action plan for preventing coronary heart disease SIR, -We believe that the action plan for preventing coronary heart disease based on assessment of multiple risk, proposed by a working group of the Coronary Prevention Group and British Heart Foundation, merits further discussion.' Carrying out the action plan is easier said than done. The practical example assumes that a practice with five doctors and two nurses will allocate a nurse to 10 health promotion clinics a week-in other words, a full time job. The experience of OXCHECK2 and the family heart study (unpublished data) confirms that the nurse needs to spend at least 45 minutes with each person who attends for a health check if high quality intervention is the aim. The action plan allows only 20 minutes per appointment, which is insufficient to establish the health needs of a person and offer tailored advice. Even with a full time nurse offering only 20 minute appointments, after 3000 health checks required by the general practice contract have been done only 1500 follow up appointments are left. The working group expects each practice to have 1000 "clinical risk patients," or 333 each year for three years, and simply to record a mean of three cholesterol or blood pressure readings for each of these would require another 1000 appointments a year. This leaves 500 appointments for following up the multiple risk group-that is, one appointment for 500 of the 3000 screened, two appointments for 250 of the 3000, or three appointments for only 125 of the 3000. During this screening and follow up programme, of course, the nurse has been removed from other duties, so the practice's usual treatment room services are halved. The cost of this screening and follow up can be measured in dressings not done, opportunities for family planning missed, diabetes and asthma clinics curtailed, and all the other clinical practices in which the nurse would otherwise be engaged. If coronary heart disease can be reduced by this type of health promotion clinic-and the answer to that question is still not clear-a huge commitment in nursing and administrative time is needed. This must come either from present resources, in which case our disease treatment service must be reduced, or from new investment in primary care. Unless this is forthcoming, coronary heart disease prevention clinics will touch only the tip of the iceberg. ANN-LOUISE KINMONTH GERAINT DAVIES Faculty of Medicine, Aldermoor Health Centre, Southampton SO I 6ST
1 Working Group of the Coronary Prevention Group and the British Heart Foundation. An action plan for preventing coronary heart disease in primary care. BMJ 1991;303:748-50. (28 September.) 2 Imperial Cancer Research Fund OXCHECK Study Group. Prevalence of risk factors for heart disease in OXCHECK trial: implications for screening in primary care. BM 1991;302: 1057-60. (4 May.)
Coronary risk-disk SIR,-Hugh Tunstall-Pedoe proposes that the acid test of his coronary risk-disk should be its usefulness.' It is certainly impressive that good predictions are obtained in a population different from the parent population, but it is in the application to individuals that we are concerned. One of us (GHH) estimated his five year absolute risk of coronary event as' 18% with the logistic formula. This compares with a 13% risk if he was normotensive, had a normal cholesterol concentration, and had never smoked. The 5% reduction attainable by changing his lifestyle implies that 20 people like him will have to change their habitsassuming this is effective-to save one coronary event. Would he be the lucky one? Moreover, the high standard error of the coefficient of the group of ex-smokers provides a range for his risk of 12-26%. This uncertainty suggests that it may be better to use the equation; an ordinary pocket scientific calculator with a memory and logarithmic functions will give the result in less than 30 seconds-it is cheaper than a risk disk and more versatile. Actually doing the calculations reminds one ofthe basis of interpreting risk-a regression equation with the problems of interdependence between variables which are usually ignored but may be very important. The main use of the risk disk would be in targeting health promotion on those most in need. We believe that a statement of absolute risk is far more likely to be effective than identifying the tenth of the population in which the patient belongs, particularly if the middle tenths are to be ignored in favour of the top 20%, who are likely to suffer 40% of coronary events. There is the potential for promoting a false sense of security, which would not occur with the absolute risk, as in the example ofWTH, whose risk is still 2% despite him being in one of the lower tenths. The test of usefulness must be a measure of the effect of using the disk on coronary morbidity and mortality over five years. Perhaps it is premature to engage in fortune telling until we have the result of such a study. G H HALL Exeter EX2 4NT W T HAMILTON Exeter EXI 1 SR I Tunstall-Pedoe H. The Dundee coronary risk-disk for management of change in risk factors. BMJ 1991;303:744-7. (28
September.)
Imported HIV infection acquired heterosexually SIR,-In view of the increasing workload at our clinic and nationally resulting from HIV infection acquired heterosexually we reviewed the epidemiological data on our female patients infected with HIV. To date 75 women infected with HIV have been under the care of the departments of genitourinary medicine of St Mary's Hospital and Central Middlesex Hospitals in central London. Four of these patients have had an AIDS defining illness. The table shows the risk factors for acquisition of HIV infection among these patients. Forty of the women acquired their infections abroad through heterosexual intercourse. Of these 40, 34 were African nationals who had recently
BMJ VOLUME 303
26 OCTOBER 1991
