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Manini TM, Everhart JE, Patel KV, et al. Daily Activity Energy Expenditure and Mortality Among Older Adults. JAMA. 2006;296(2):171–179. doi:10.1001/jama.296.2.171
Author Affiliations: National Institute on Aging, Laboratory of Epidemiology, Demography and Biometry (Drs Manini, Patel, and Harris) and National Institute of Diabetes and Digestive and Kidney Diseases (Dr Everhart), Bethesda, Md; Departments of Nutritional Sciences (Dr Schoeller) and Kinesiology (Dr Colbert), University of Wisconsin, Madison; Institute of Health Sciences, Faculty of Earth and Life Sciences, VU University and Institute for Research in Extramural Medicine, VU University Medical Center, Amsterdam, the Netherlands (Dr Visser); Department of Biostatistics and Epidemiology, University of Tennessee, Memphis (Dr Tylavsky); Department of Medicine, University of California, San Francisco (Dr Bauer); and Division of Endocrinology and Metabolism, University of Pittsburgh Medical Center, Pittsburgh, Pa (Dr Goodpaster).
Context Exercise is associated with mortality benefits but simply expending energy through any activity in an individual's free-living environment may confer survival advantages.
Objective To determine whether free-living activity energy expenditure is associated with all-cause mortality among older adults.
Design, Setting, and Participants Free-living activity energy expenditure was assessed in 302 high-functioning, community-dwelling older adults (aged 70-82 years). Total energy expenditure was assessed over 2 weeks using doubly labeled water. Resting metabolic rate was measured using indirect calorimetry and the thermic effect of meals was estimated at 10% of total energy expenditure. Free-living activity energy expenditure was calculated as: (total energy expenditure × 0.90) − resting metabolic rate. Participants were followed up over a mean of 6.15 years (1998-2006).
Main Outcome Measures Free-living activity energy expenditure (3 tertiles: low, <521 kcal/d; middle, 521-770 kcal/d; high, >770 kcal/d) and all-cause mortality.
Results Fifty-five participants (18.2%) died during follow-up. As a continuous risk factor, an SD increase in free-living activity energy expenditure (287 kcal/d) was associated with a 32% lower risk of mortality after adjusting for age, sex, race, study site, weight, height, percentage of body fat, and sleep duration (hazard ratio, 0.68; 95% confidence interval, 0.48-0.96). Using the same adjustments, individuals in the highest tertile of free-living activity energy expenditure were at a significantly lower mortality risk compared with the lowest tertile (hazard ratio, 0.31; 95% confidence interval, 0.14-0.69). Absolute risk of death was 12.1% in the highest tertile of activity energy expenditure vs 24.7% in the lowest tertile; absolute risks were similar to these for tertiles of physical activity level. The effect of free-living activity energy expenditure changed little after further adjustment for self-rated health, education, prevalent health conditions, and smoking behavior. According to self-reports, individuals expending higher levels of free-living activity energy were more likely to work for pay (P = .004) and climb stairs (P = .01) but self-reported high-intensity exercise, walking for exercise, walking other than for exercise, volunteering, and caregiving did not differ significantly across the activity energy expenditure tertiles.
Conclusions Objectively measured free-living activity energy expenditure was strongly associated with lower risk of mortality in healthy older adults. Simply expending energy through any activity may influence survival in older adults.
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