The association between body mass index and incident hypertension in rural women in China

Background/Objectives: To evaluate the association between body mass index (BMI) and incident hypertension in a cohort of rural women in the Chinese population. Subjects/Methods: A population-based sample of 11 468 rural Chinese women aged >= 35 years and free from hypertension at baseline were followed-up from 2004-2006 to 2008. We calculated BMI from measured weight and height. Incident hypertension was defined as systolic blood pressure (BP) >= 140 mm Hg, diastolic BP >= 90 mm Hg or current use of antihypertensive medications. Results: During a median follow-up of 28 months, 2666 participants developed hypertension. Higher baseline BMI, even within the 'normal' range, was consistently associated with an increased risk of hypertension. Compared with participants in the lowest BMI quintile (18.5-21.1 kg/m(2)), the multivariable-adjusted relative risks (95% confidence interval) of developing hypertension for women with a BMI of 21.2 to 22.4, 22.5 to 23.7, 23.8 to 25.4 and >= 25.4 kg/m(2) were 1.200 (1.058-1.361), 1.250 (1.100-1.419), 1.466 (1.291-1.666) and 1.785 (1.584-2.012), respectively (P for trend, <0.001). Further adjustment for baseline BP did not substantially alter these results. We found similar associations using other BMI categories and after excluding women with smoking history at baseline. The pattern of association also existed among old women (age >= 55 years). Conclusions: In this large cohort, we found a strong gradient association between higher BMI and increased risk of hypertension, even among older women within the normal BMI range. Clinicians should emphasize the importance of weight management for the primary prevention of hypertension in rural women in the Chinese population. European Journal of Clinical Nutrition (2010) 64, 769-775; doi: 10.1038/ejcn.2010.97; published online 9 June 2010