Comparison of weight in middle age, weight at 18 years, and weight change between, in predicting subsequent 14 year mortality and coronary events: Caerphilly Prospective Study

Abstract

Objective - The prevalence of obesity is increasing in many European countries and in the United States. This report examines the mortality and morbidity associated with being overweight and obese in the Caerphilly Prospective Study and the relative effects of weight in middle age and self reported weight at 18 years. Design - All men aged 45 to 59 years from the town of Caerphilly, South Wales and outlying villages were identified and 2512 men were examined for the first time between 1979 and 1983. Men were asked to recall their weight at 18 years of age (when the majority had been examined for National Service) so that weight then, weight at screening, and the difference could be related to their 14 year follow up from screening. A total of 2335 men could recall their weight at 18 years. By 14 years of follow up from screening 465 men had died and 382 had had coronary events. Results - Mean body mass index in men who reported their weight at 18 years was 22.3 (SD) 2.8) kg/m2 and only 41 of these men (1.8%) were classified as obese (index ≥ 30 kg/m2). The index did not predict all cause mortality when examined by quintile. For major ischaemic heart disease (non-fatal or fatal ischaemic heart disease) the relative odds was 1.73 (95% CI 1.21, 2.48) in the top fifth of the distribution (body mass index ≥ 24.2 kg/m2) compared with the bottom fifth (body mass index < 20.1 kg/m2). In men with an index ≥ 30 kg/m2 however, the relative odds were 2.03 (95% CI, 1.03, 4.01) for all cause mortality and 2.17 (95% CI, 1.08, 4.34) for major ischaemic heart disease, adjusted for age, smoking habit and social class. When men were recruited to the study, from 1979 to 1983; the mean body mass index had increased to 26.2 (SD 3.6), a mean increase of 3.9 kg/m2 or 11.2 kg; 299 men (12.1%) were classified as obese and showed significantly increased relative odds of both all cause mortality (1.53 (95% CI 1.14, 2.06) and major ischaemic heart disease (1.55 (95% CI 1.13, 2.11)), adjusted for age, smoking habit and social class relative to the non-obese men. The effect of gain in weight from 18 years to recruitment was also examined; all cause mortality showed highest mortality in the fifth of the distribution who experienced weight loss or minimal weight gain. For major ischaemic heart disease an inconsistent, weak trend was shown, the relative odds rising to a maximum of 1.26 (0.89, 1.80) in the top fifth of weight gain compared with the bottom fifth. Weight gain showed strong associations with potential cardiovascular risk factors measured at recruitment; insulin, triglyceride, glucose, diastolic and systolic blood pressure and high density lipoprotein-cholesterol. Conclusions - Body mass at 18 years of age of 30 kg/m2 or more conferred increased risk for all cause mortality and major ischaemic heart disease during 14 years of follow up of men aged 45 to 59 years. By the baseline examination the prevalence of obesity (body mass index ≥ 30) had increased from 1.8% to 12.1%; obese men also showed an excess risk of major ischaemic heart disease and overall mortality, but these risks were lower than those predicted from 18 years of age. Weight gain was strongly associated with smoking habit, the greatest weight gain being among ex-smokers and the least among light smokers. Weight gain from 18 years of age to baseline examination showed little relation with subsequent mortality and risk of major ischaemic heart disease when adjusted for age, smoking habit and social class. The lowest mortality rate occurred in the 'fifth' of men who gained a mean weight of 16.1 kg. Weight gain is closely associated with some adverse cardiovascular risk factors; in particular with insulin, triglyceride, glucose and diastolic blood pressure.