Body mass index and mortality from ischaemic heart disease in China: a 15-year prospective study on 220 000 adult men

Abstract

To assess the relationship between body mass index (BMI) and ischaemic heart disease (IHD) mortality, especially in populations with low mean BMI levels. We examined the data from a population-based, prospective cohort study of 220 000 Chinese men aged 40 - 79, who were enrolled in 1990 - 1991, and followed up ever since to 1/1/2006. Relative risks of the deaths from IHD by the baseline BMI were calculated, after controlling age, smoking, and the other potential confounding factors. The mean baseline BMI was 21.7 kg/m(2), and 2763 IHD deaths were recorded during the 15-year follow-up (6.8% of all deaths) program. Among men without prior vascular diseases at baseline, there was a J-shaped association between BMI and IHD mortality. When baseline BMI was above 20 kg/m(2), there was a strongly positive association of BMI with IHD risk, with each 5 kg/m(2) higher in BMI associated with 21% (95%CI: 9% - 35%, P = 0.0004) higher IHD mortality. Below this BMI range, the association appeared to be reverse, with the risk ratios as 1.00, 1.11, and 1.14, respectively, for men with BMI 20 - 21.9, 18 - 19.9, and < 18 kg/m(2). The excess IHD risk observed at low BMI levels persisted after restricting analysis to never smokers or excluding the first 3 years of follow-up. Lower BMI was associated with lower IHD risk among people in the so-called 'normal range' of BMI values (20 - 25 kg/m(2)). However, below that range, the association might well be reversed.