Objective Measures of Physical Activity, Fractures and Falls: The Osteoporotic Fractures in Men Study

OBJECTIVES: To determine the association between objectively measured physical activity (PA), fractures, and falls. DESIGN: Longitudinal cohort study. SETTING: Six U.S. clinical sites. PARTICIPANTS: Two thousand seven hundred thirty-one men with a mean age of 79. MEASUREMENTS: Total and active energy expenditure (EE) and minutes per day spent in sedentary and moderate intensity activities were measured for at least 5 days. Energy expended at a metabolic equivalent of greater than three was termed active EE. Incident nonspine fractures and falls were identified every 4 months. RESULTS: Seven hundred fifty-nine (28.2%) men fell at least once over 12 months of follow-up; 186 (6.8%) experienced one or more fractures over an average follow-up of 3.5 +/- 0.9 years. The association between PA and falling varied according to age (P interaction = .02). Men younger than 80 with the lowest active EE had a lower risk of falling than men with the highest active EE (relative risk (RR) = 0.75; P trend = .08), whereas men aged 80 and older with the lowest active EE had a higher risk of falling than men with the highest active EE (RR = 1.43, P trend = .09). In multivariate models including health status, men in the lowest quintile of active EE had a significantly higher risk of fracture (hazard ratio (HR) = 1.82, 95% confidence interval (CI) = 1.10-3.00, P trend = .04) than men in highest quintile. Men with < 33 min/d of moderate activity had a 70% greater risk of fracture (HR = 1.70, 95% CI = 1.03-2.80). CONCLUSION: Age modifies the association between PA and falling. Interventions aimed at obtaining more than 30 minutes of moderate PA per day may reduce fractures, extending PA guidelines to the oldest old, the fastest-growing proportion of those aged 65 and older.