Gender differences in modifiable risk factors for hip fracture: 10-year follow-up of a prospective study of 0.5 million Chinese adults.

BACKGROUND: Little is known about the incidence rates and importance of major modifiable risk factors for hip and major osteoporotic fractures in low- and middle-income countries. We estimated the age- and sex-specific incidence of hip, major osteoporotic, and any fractures and their associated risk factors in Chinese adults. METHODS: This was a prospective study of 512,715 adults, aged 30-79 years, recruited from 10 diverse areas in China from 2004 to 2008 and followed up for 10 years. Age- and sex-specific incidence rates were estimated, and Cox regression was used to yield adjusted hazard ratios (HRs) and population attributable fractions for risk factors. RESULTS: The incidence rates of hip fracture in Chinese adults were 5.1 (95% confidence interval [CI] 5.0-5.3) per 10,000 person-years; they were higher in women than in men and increased by two- to threefold per 10-year older age. Among men, five risk factors for hip fracture, including low education (HR = 1.23; 95% CI 1.04-1.45), regular smoker (1.22, 1.03-1.45), lower weight (1.59, 1.34-1.88), alcohol drinker (1.18, 1.02-1.36), and prior fracture (1.62, 1.33-1.98), accounted for 44.3% of hip fractures. Among women, lower weight (1.30, 1.15-1.46), low physical activity (1.22, 1.10-1.35), diabetes (1.62, 1.41-1.86), prior fracture (1.54, 1.33-1.77), and self-rated poor health (1.29, 1.13-1.47) accounted for 24.9% of hip fractures. Associations of risk factors with major osteoporotic or any fractures were weaker than those with hip fractures. CONCLUSIONS: The age- and sex-specific incidence rates of hip fracture in Chinese adults were comparable with those in Western populations. Five potentially modifiable factors accounted for half of the hip fractures in men and one quarter in women.