BACKGROUND AND PURPOSE:

• Physical activity is associated with reduced hip fracture risk but data unclear regarding other fracture sites
• LaMonte et al. (JAMA Netw Open., 2019) analyzed the associations of physical activity vs sedentary behavior with fracture incidence among postmenopausal women

METHODS:

• Prospective cohort study
  • Women’s Health Initiative
• Participants
  • Postmenopausal women, 50 to 79 years of age
• Exposures
  • Self-reported physical activity and sedentary time
• Study design
  • Enrollment between October 1993 and December 1998 at 40 US clinical centers
  • Observed outcomes through September 2015
• Definitions of ‘activity’
  • Strenuous: Exercise resulting in sweating and a fast heartbeat (e.g., aerobics, jogging, tennis, or swimming laps)
  • Moderate: Less exhausting activities (e.g., biking outdoors, exercise machines, calisthenics, easy swimming, or popular or folk dancing)
  • Mild: Examples included slow dancing, bowling, or golf
  • Walking: Following questions were used
    • “How often do you walk outside the home for more than 10 minutes without stopping”
    • “When you walk outside the home for more than 10 minutes without stopping, for how many minutes do you usually walk”
• Primary outcome
  • Hazard ratio (HRs) and 95% CIs for total and site-specific fracture incidence

RESULTS:

• A total of 77,206 women were enrolled
  • Mean age, 63.4 years | 85.6% of women were white
  • Mean follow-up: 14.0 years | 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 to 0.95; P for trend < 0.001)
• Inverse associations with hip fracture were also observed for
  • Walking
    • >7.5 MET h/wk vs none
    • HR 0.88 (95% CI, 0.78 to 0.98; P for trend = 0.01)
  • Mild activity
    • HR 0.82 (95% CI, 0.73 to 0.93; P for trend = 0.003)
  • Moderate to vigorous activity
    • HR 0.88 (95% CI, 0.81 to 0.96; P for trend = 0.002)
  • Yard work
    • HR 0.90 (95% CI, 0.82 to 0.99; P for trend = 0.04)
• Total activity was positively associated with knee fracture
  • >17.7 MET h/wk vs none
  • HR, 1.26 (95% CI, 1.05 to 1.50; P for trend = 0.08)
• Mild activity was inversely associated with
  • Clinical vertebral fracture
    • HR 0.87 (95% CI, 0.78 to 0.96; P for trend =0 .006)
  • Total fractures
    • HR 0.91 (95% CI, 0.87 to 0.94; P for trend < 0.001)
• Moderate to vigorous activity was positively associated with wrist or forearm fracture
  • HR 1.09 (95% CI, 1.03 to 1.15; P for trend =0 .004)
• Sedentary time was positively associated with total fracture risk (adjusted for covariates and total physical activity)
  • >9.5 h/d vs <6.5 h/d
  • HR 1.04 (95% CI, 1.01 to 1.07; P for trend = 0.01)
• Higher total activity lessened some of the total fracture risk associated with sedentary behavior

CONCLUSION:

• For older women, higher total physical activity was associated with a lower risk of total and hip fractures
  • However, it was also associated with a higher risk of knee fractures
  • Moderate to vigorous activity was also associated with wrist and forearm fractures
• Even mild activity and walking were potentially beneficial and associated with lower hip fracture risk
  • Prior to this study, data has been inconclusive as to the benefit of mild activity to reduce hip fractures
• The authors conclude

If confirmed, future recommendations on fracture prevention in postmenopausal women should promote light PA, especially in those who are frail and unable to safely engage in more intense activities. Sedentary behavior as an independent factor predisposing individuals to fracture requires further investigation

Learn More – Primary Sources:

Association of Physical Activity and Fracture Risk Among Postmenopausal Women

Related ObG Topics:

Osteoporosis Treatment for Postmenopausal Women at High Risk for Fracture

ACP Releases Guidance Update on Osteoporosis Treatment

Hip Fractures in Older Women: Who is at Risk and Would Benefit Most from Treatment?

Is There an Optimal Time-to-Surgery Threshold for Hip Fracture Surgery?

How Does Exercise Affect Health Postmenopause?