Association of physical activity and sitting time with femoral bone health among older cancer survivors.

Introduction: Our primary goal was to investigate the independent and combined associations of physical activity (PA) and sitting time (ST) with femoral bone health among cancer survivors aged 60 or older.

Materials and methods: This cross-sectional study included 1159 cancer survivors aged 60 years or older who underwent femur dual-energy X-ray absorptiometry (DXA) examination from continuous National Health and Nutrition Examination Survey data sets. PA and ST were assessed by self-report, and bone health included bone mineral density (BMD) at all femoral sub-regions, osteopenia/osteoporosis of femoral neck, and total fracture. The independent and combined associations of PA and ST with femoral bone health were determined using multivariable linear or logistic regression analyses.

Results: More than 40% cancer survivors reported engaging in PA < 150 min/week with ST ≥ 6 h/d. PA solely showed no association with bone health at femur sites. Prolonged ST was associated with lower femur's BMD, higher prevalence of osteopenia/osteoporosis, and total fracture. Specifically, the negative association of prolonged ST and femur's BMD was shown in PA ≥ 150 min/week group, but not in PA < 150 min/week group. In combined analysis, prolonged ST with PA ≥ 150 min/week showed the strongest negative associations with femur's BMD.

Conclusion: PA appears not to be directly associated with femoral bone health. Higher ST is associated with lower BMD and a higher incidence of total fractures, regardless of PA level, among cancer survivors aged 60 or older.