[Association between body mass index and calcaneus bone mineral density in adults in a cross-sectional study in Tongxiang, Zhejiang Province].

Objective: To evaluate the association between body mass index (BMI) and bone mineral density of calcaneus in adults. Methods: Data of the second resurvey of China Kadoorie Biobank study from Tongxiang of Zhejiang Province were used. A total of 2 896 participants aged 44-84 years were included in the final analysis. Overweight was defined as 23.0 kg/m2≤BMI<25.0 kg/m2, and obesity was defined as BMI ≥25.0 kg/m2 based on the criteria recommended by WHO/West Pacific Region. Multiple linear regression model was used to evaluate the association between BMI and calcaneus bone mineral density. Restricted cubic splines were used to investigate the dose-response relationship between BMI and calcaneus bone mineral density. Results: The calcaneus bone mineral density in the study subjects were as follow (x±SE): the broadband ultrasound attenuation was (109.4±12.1) dB/MHz, the speed of ultrasound was (1 545.9±33.8) m/s, and the stiffness index was 85.7±15.8. After adjusting for socio-demographic factors, lifestyle, waist circumference, diabetes and hypertension prevalence, BMI was positively associated with calcaneus stiffness index in non-overweight and non-obese adults, with β of 2.30 (95%CI: 1.11-3.49) for men (P<0.001) and 1.08 (95%CI: 0.38-1.78) for women (P=0.003), respectively. In addition, BMI was positively associated with calcaneus stiffness index in overweight and obese women (β=0.90, 95%CI: 0.38-1.42) (P<0.001), and null association was found in overweight and obese men (β=0.06, 95%CI: -0.92-1.04) (P=0.900). Restricted cubic spline model showed a nonlinear dose-response relationship between BMI and calcaneus stiffness index. Conclusion: Non-linear association was found between BMI with calcaneus bone mineral density in adults.