Association between change in body weight after midlife and risk of hip fracture-the Singapore Chinese Health Study

The relationship between change in body weight and risk of fractures is inconsistent in epidemiologic studies. In this cohort of middle-aged to elderly Chinese in Singapore, compared to stable weight, weight loss >= 10 % over an average of 6 years is associated with nearly 40 % increase in risk of hip fracture. Introduction Findings on the relationship between change in body weight and risk of hip fracture are inconsistent. In this study, we examined this association among middle-aged and elderly Chinese in Singapore. Methods We used prospective data from the Singapore Chinese Health Study, a population-based cohort of 63,257 Chinese men and women aged 45-74 years at recruitment in 1993-1998. Body weight and height were self-reported at recruitment and reassessed during follow-up interview in 1999-2004. Percent in weight change was computed based on the weight difference over an average of 6 years, and categorized as loss >= 10 %, loss 5 to < 10 %, loss or gain < 5 % (stable weight), gain 5 to < 10 %, and gain >= 10 %. Multivariable Cox proportional hazards regression model was applied with adjustment for risk factors for hip fracture and body mass index (BMI) reported at follow-up interview. Results About 12 % experienced weight loss >= 10 %, and another 12 % had weight gain >= 10 %. After a mean follow-up of 9.0 years, we identified 775 incident hip fractures among 42,149 eligible participants. Compared to stable weight, weight loss >= 10 % was associated with 39 % increased risk (hazard ratio 1.39; 95 % confidence interval 1.14, 1.69). Such elevated risk with weight loss >= 10 % was observed in both genders and age groups at follow-up (<= 65 and > 65 years) and in those with baseline BMI >= 20 kg/m(2). There was no significant association with weight gain. Conclusions Our findings provide evidence that substantial weight loss is an important risk factor for osteoporotic hip fractures among the middle-aged to elderly Chinese.