Relationships Between Sedentary Behavior, Physical Activity And Body Composition With Bone Mineral Density In Postmenopausal Women

PURPOSE: Several studies have shown that sedentary behavior and lack of physical activity (PA) are risk factors for bone mineral density (BMD), however, the results of studies about the relationships between physical activity, body composition and BMD have varied. Therefore, the main purpose of this study is to explore the relationship between accelerometer-determined PA and body composition, BMD in aged 50-80 postmenopausal women. METHODS: A total of 135 eligible postmenopausal women (age = 64.0 ± 5.4 years; height = 157.1 ± 5.3 cm; weight = 60.7 ± 9.3 kg) were recruited in this study. Body composition and BMD were measured by dual-energy X-ray absorptiometry (GE Lunar Prodigy, USA), and 7-day physical activity data were collected by triaxial accelerometer (Actigraph GT3X-BT, USA). According to the World Health Organization, T-score > -1.0 is defined as normal BMD, while a -1.0 > T-score > -2.5 is defined as osteopenia, and T-score < -2.5 indicates osteoporosis; subjects was divided into two groups: normal group (n = 73, BMI = 25.5 ± 3.5) and osteopenia group (n = 62, BMI = 23.5 ± 3.1). RESULTS: 1) The body weight, fat content, fat-free mass of normal group were significantly higher than those of osteopenia group (63.1 ± 9.2 kg VS 57.9 ± 8.6 kg; 23.5 ± 6.4 kg VS 20.3 ± 5.8 kg; 39.5 ± 4.1 kg VS 37.6 ± 3.7 kg; all p < 0.01). 2) There were no significant differences between normal group and osteopenia group in sedentary behavior and duration of physical activity at all levels (all p > 0.05). 3) There was no significant correlation between sedentary behavior, physical activity and regions BMD and whole-body BMD. LPA, MVPA time are negatively correlated with fat content and body fat percentage in a very low degree (r = -0.172, p = 0.046, r = -0.233, p = 0.006; r = -0.258, p = 0.003, r = -0.270, p = 0.002). Body weight, fat content and fat free mass are positively correlated with regions of the femur (femoral neck, Ward’s triangle, greater trochanter) BMD, the lumbar spine BMD (r = 0.492, r = 0.385, r = 0.531, all p < 0.001) and whole-body BMD (r = 0.355, r = 0.306, r = 0.332, all p < 0.001) in different degrees. CONCLUSION: Body composition, especially body weight and fat free mass, are factors affecting BMD of postmenopausal women, while sedentary behavior and physical activities at all levels are not directly related to BMD. SM202110051003