Body weight and mortality in middle aged British men: impact of smoking.

OBJECTIVE--To assess the relation between body mass index and mortality in middle aged British men. DESIGN--Men who were recruited for the British Regional Heart Study were followed up for a mean of nine years. SETTING--General practices in 24 British towns. SUBJECTS--7735 Men aged 40-59 years selected from the age-sex registers of one group practice in each of the 24 towns. MAIN OUTCOME MEASURE--Mortality from cardiovascular and non-cardiovascular causes. RESULTS--660 Of the men died. There was a U-shaped relation between body mass index and total mortality. Very lean men (less than 20 kg/m2) had by far the highest mortality followed by lean men (20-22 kg/m2) and obese men (greater than or equal to 28 kg/m2). The high mortality in lean and very lean men was due largely to non-cardiovascular causes, particularly lung cancer and respiratory disease, which are associated with cigarette smoking. In obese men deaths were more likely to be due to cardiovascular causes. There was a strong inverse association between body weight and cigarette smoking. When the pattern of mortality was examined by age, smoking habits, and pre-existing smoking related disease both very lean men and obese men consistently had an increased mortality. The U-shaped relation was most prominent in men in the oldest age group (55-59). Current smokers had a higher mortality than former smokers at virtually all values of body mass index. An increased mortality in lean men was seen only in current smokers and in men with smoking related disease. Among men who had never smoked, lean men had the lowest total mortality, thereafter mortality increased with increasing body mass index (p less than 0.01). CONCLUSIONS--This study provides strong evidence of the impact of cigarette smoking on body weight and mortality and strongly suggests that the benefits of giving up smoking are far greater than the problems associated with the increase in weight that may occur.