(J Epidemiol Community Health 1998;52:20-26) Despite the large amount of medical literature available on the subject, the relations of body weight, body fatness, and related measures to disease and mortality require further investigation mainly in the search for optimal weight with regard to the best health status and health perspectives. 1-11On the other hand it has taken years for the acceptance of the concept of a J or U shaped relation of body weight and related measures to mortality, 4 8 9 12 and recently the desirable body weight for elderly people seems to be higher than previously claimed.Extensive studies based on population samples with adequate follow up in Italy are limited. For example, the Italian cohorts of the Seven Countries Study could be followed up for 25 years, 13 but they were made only for middle aged men. A larger and more recent analysis, based on the pooling of a few studies, suggested the existence of a parabolic inverse J shaped relation of some parameters of obesity to 10 year mortality, although the step of the left branch of the curve could be reduced by the exclusion of smokers, early deaths, and people carrying serious health conditions at entry. 14The availability of data from the Italian RIFLE (Risk Factors and Life Expectancy) pooling project, 15 including many population samples spread all over the country and large numbers, oVers the possibility to provide more consistent material although based on very simple measures of body fatness.The purpose of this analysis is to describe the relation of body mass index to short-term mortality in a large population sample of men and women in Italy. Methods STUDY POPULATIONThe RIFLE Pooling Project includes epidemiological data from nine diVerent large scale population studies started in Italy between 1978 and 1987 and focused on cardiovascular diseases or other chronic conditions. 15 The nine studies gathered 52 population samples of men and women in the age range of 20 to 69 years. Each sample, except two, were identified by electoral rolls (where all people aged 18 plus are enlisted) in defined geographical areas. Two samples were of occupational origin (large companies with a prevalence of sedentary employees), both located in Rome. The average participation rate was around 70%, while subjects lost to follow up at six years were 2.1%.Only 47 cohorts, however, spread across 13 of the 20 Italian regions, were finally considered because, for the remaining five, a minimum follow up could not be completed.These nine studies proved suitable for pooling because all of them were conducted or coordinated or methodologically advised by the same centre and most of the measurements were made using the same standardisation and quality control procedures.
Three large-scale epidemiological surveys covering some major coronary risk factors were conducted in Italy in population samples of men and women aged 30-59 years. The first survey was carried out in 1978-1979 (RF2 study; nine samples in eight regions; 2561 men and 2912 women); the second in 1983-1984 (OB43 study; nine samples in the same eight regions; 2267 men and 2398 women); and the third one in 1985-1987 (MICOL study; 18 samples in 10 regions; 14,411 men and 12,611 women). Time trends in mean age standardized risk factors levels showed slight but systematic decreases in blood pressure, cigarette smoking (only in men), and body mass index (only in women); whereas no substantial changes were observed in serum cholesterol levels. The combined multiple coronary risk estimated by a model produced in a previous study, showed a decline between 1978-1979 and 1983-1984 of 5.5% in men and 13.4% in women. These changes were compared with the official coronary death rates between 1984 and 1987 in the whole country and in the regions where the samples were located. The expected/observed ratio computed in different ways ranged from 0.54 to 0.88 for men and was over 1 for women. Changes in the levels of major risk factors and changes in coronary mortality seem biologically coherent at least in men.
Two population samples of men aged 46-65 years were examined for the measurement of some cardiovascular risk factors and followed up for 6.5 years. The two groups were: 1) 3338 men belonging to occupational groups examined in Rome (ROG) in 1979-81 and 2) 1543 men belonging to two demographic samples of rural areas located in northern and central Italy (IRA) examined in 1965. In men free from previous myocardial infarction the rate of fatal coronary events was 18.0 in the ROG group and 17.5 per 1000 in the IRA group. Five established risk factors (age, systolic blood pressure, serum cholesterol, cigarette consumption and body mass index) were used in a multivariate model for predicting coronary deaths. The coefficients of the multiple logistic function were similar in the two populations group. However, when the IRA coefficients were applied to the ROG factors, they predicted 43 events instead of 58 (under-estimation of 26%; p < 0.05), whereas the ROG coefficients predicted 31 events instead of 26 in the IRA sample (over-estimation of 19%; p = n.s.). A model which included the pool of the two populations and a dummy-variable for the identification of each of them, suggested that being a member of the ROG group is accompained, everything else being equal, by an extra risk of 26%.
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