Association between body composition components and bone mineral density in older adults

To investigate the correlation between body composition and bone mineral density (BMD) in middle-aged and older adults of different sex and body mass index (BMI) groups. A total of 1623 middle-aged and elderly people (aged 50 years and above) who underwent physical examination at the Health Management Center of the International Medical Service of Peking Union Medical College Hospital (Xidan Branch) from January 2020 to June 2024 were selected as the study objects. Demographic characteristics, laboratory examination, body composition and BMD measured by dual-energy X-ray absorptiometry (DXA) were collected. According to sex and BMI, the subjects were divided into normal weight group (18.5kg/m2 ≤ BMI < 24 kg/m²), overweight group (24kg/m2 ≤ BMI < 28 kg/m²) and obese group (BMI ≥ 28 kg/m²). One-way analysis of variance was used to compare the differences among the three groups. Multiple regression model was used to analyze the correlation between BMI, body composition and BMD. There were 874 males (267 normal weight group, 430 overweight group and 177 obesity group) and 749 females (415 normal weight group, 258 overweight group and 76 obese group). There were significant differences in laboratory results, body composition and BMD in male and female groups (all P < 0.05). After adjusting for age, smoking and drinking history, hypertension and diabetes history, multiple regression analysis showed that BMI was significantly positively correlated with lumbar spine, left femoral neck and total hip joint BMD in male obese group and overweight group compared with normal body weight group (all P < 0.05). With the increase of BMI, BMD in all parts also increased, total hip BMD in the obese group was most significant increased (β = 0.08, 95%CI 0.05-0.10, p < 0.0001);The correlation between BMI and BMD of female subjects was similar to that of male subjects, in which the BMD of lumbar spine and total hip joint in increased the most in obese group (β = 0.09, 95%CI 0.05-0.13, p < 0.0001) and (β = 0.09, 95%CI 0.06-0.12, p < 0.0001). The correlation between body composition and BMD was further analyzed. Regardless of BMI group, skeletal muscle mass (SMM), skeletal muscle index and fat-free body mass (FFM) of male and female were significantly positively correlated with BMD of all parts (P < 0.05). Body fat percentage (PBF) in male obesity group was negatively correlated with BMD in all parts (P < 0.05), while female body fat percentage (PBF) was negatively correlated with BMD in lumbar spine and hip joint in overweight group (P < 0.05). Increases in BMI, SMM and FFM are beneficial to bone health, but high PBF may be harmful to bone health.