Department of Epidemiology and Environmental Health, University at Buffalo, The State University of New York, Buffalo.
Data Coordinating Center, Fred Hutchinson Cancer Research Center, Seattle, Washington.
JAMA Netw Open. 2019 Oct 2;2(10):e1914084. doi: 10.1001/jamanetworkopen.2019.14084.
Physical activity is inversely associated with hip fracture risk in older women. However, the association of physical activity with fracture at other sites and the role of sedentary behavior remain unclear.
To assess the associations of physical activity and sedentary behavior with fracture incidence among postmenopausal women.
DESIGN, SETTING, AND PARTICIPANTS: The Women's Health Initiative prospective cohort study enrolled 77 206 postmenopausal women aged 50 to 79 years between October 1993 and December 1998 at 40 US clinical centers. Participants were observed for outcomes through September 2015, with data analysis conducted from June 2017 to August 2019.
Self-reported physical activity and sedentary time.
Hazard ratios (HRs) and 95% CIs for total and site-specific fracture incidence.
During a mean (SD) follow-up period of 14.0 (5.2) years among 77 206 women (mean [SD] age, 63.4 [7.3] years; 66 072 [85.6%] white), 25 516 (33.1%) reported a first incident fracture. Total physical activity was inversely associated with the multivariable-adjusted risk of hip fracture (>17.7 metabolic equivalent [MET] h/wk vs none: HR, 0.82; 95% CI, 0.72-0.95; P for trend < .001). Inverse associations with hip fracture were also observed for walking (>7.5 MET h/wk vs none: HR, 0.88; 95% CI, 0.78-0.98; P for trend = .01), mild activity (HR, 0.82; 95% CI, 0.73-0.93; P for trend = .003), moderate to vigorous activity (HR, 0.88; 95% CI, 0.81-0.96; P for trend = .002), and yard work (HR, 0.90; 95% CI, 0.82-0.99; P for trend = .04). Total activity was positively associated with knee fracture (>17.7 MET h/wk vs none: HR, 1.26; 95% CI, 1.05-1.50; P for trend = .08). Mild activity was associated with lower risks of clinical vertebral fracture (HR, 0.87; 95% CI, 0.78-0.96; P for trend = .006) and total fractures (HR, 0.91; 95% CI, 0.87-0.94; P for trend < .001). Moderate to vigorous activity was positively associated with wrist or forearm fracture (HR, 1.09; 95% CI, 1.03-1.15; P for trend = .004). After controlling for covariates and total physical activity, sedentary time was positively associated with total fracture risk (>9.5 h/d vs <6.5 h/d: HR, 1.04; 95% CI, 1.01-1.07; P for trend = .01). When analyzed jointly, higher total activity mitigated some of the total fracture risk associated with sedentary behavior. Analysis of time-varying exposures resulted in somewhat stronger associations for total physical activity, whereas those for sedentary time were materially unchanged.
In older ambulatory women, higher total physical activity was associated with lower total and hip fracture risk but higher knee fracture risk. Mild activity and walking were associated with lower hip fracture risk, a finding with important public health implications because these activities are common in older adults. The positive association between sedentary time and total fracture risk requires further investigation.
体力活动与老年女性髋部骨折风险呈负相关。然而，体力活动与其他部位骨折的关系以及久坐行为的作用仍不清楚。
评估绝经后妇女的体力活动和久坐行为与骨折发生率的关系。
设计、地点和参与者：妇女健康倡议前瞻性队列研究纳入了 1993 年 10 月至 1998 年 12 月期间在美国 40 个临床中心的 77206 名 50 至 79 岁的绝经后女性。参与者通过 2015 年 9 月进行结果观察，数据分析于 2017 年 6 月至 2019 年 8 月进行。
自我报告的体力活动和久坐时间。
总部位和特定部位骨折发生率的危害比（HRs）和 95%置信区间（CIs）。
在 77206 名女性（平均年龄[标准差]63.4[7.3]岁；66072 名[85.6%]为白人）的平均（标准差）随访期 14.0（5.2）年中，25516 名（33.1%）报告首次发生骨折。总体体力活动与髋部骨折的多变量调整风险呈负相关（>17.7 代谢当量[MET]小时/周与无：HR，0.82；95%CI，0.72-0.95；趋势 P<.001）。与髋部骨折相关的反比关系也见于步行（>7.5 MET 小时/周与无：HR，0.88；95%CI，0.78-0.98；趋势 P=.01）、轻度活动（HR，0.82；95%CI，0.73-0.93；趋势 P=.003）、中等到剧烈活动（HR，0.88；95%CI，0.81-0.96；趋势 P=.002）和庭院工作（HR，0.90；95%CI，0.82-0.99；趋势 P=.04）。总活动与膝关节骨折呈正相关（>17.7 MET 小时/周与无：HR，1.26；95%CI，1.05-1.50；趋势 P=.08）。轻度活动与临床椎体骨折风险降低相关（HR，0.87；95%CI，0.78-0.96；趋势 P=.006）和总骨折风险（HR，0.91；95%CI，0.87-0.94；趋势 P<.001）。中等到剧烈活动与腕部或前臂骨折呈正相关（HR，1.09；95%CI，1.03-1.15；趋势 P=.004）。在控制协变量和总体力活动后，久坐时间与总骨折风险呈正相关（>9.5 小时/天与<6.5 小时/天：HR，1.04；95%CI，1.01-1.07；趋势 P=.01）。当联合分析时，较高的总活动减轻了与久坐行为相关的部分总骨折风险。对时变暴露的分析导致总体力活动的关联略有增强，而久坐时间的关联基本不变。
在活动能力良好的老年女性中，较高的总体力活动与总骨折和髋部骨折风险降低相关，但与膝关节骨折风险升高相关。轻度活动和步行与髋部骨折风险降低相关，这一发现具有重要的公共卫生意义，因为这些活动在老年人中很常见。久坐时间与总骨折风险的正相关关系需要进一步研究。
