Author Affiliations: Rush Alzheimer's Disease Center (Drs Buchman, Yu, Boyle, Shah, and Bennett) and Departments of Neurological Sciences (Drs Buchman, Yu, and Bennett), Behavioral Sciences (Dr Boyle), and Family Medicine (Dr Shah), Rush University Medical Center, Chicago, Illinois.
Increased levels of exercise are currently recommended to improve health and increase longevity, but gaps in our knowledge impede the formulation of evidence-based recommendations, particularly in older individuals.1 Most studies of physical activity in old age have focused on self-reported physical activity measures, which are affected by recall bias. Moreover, few studies have examined the contribution of nonexercise physical activity to survival in old age.2- 4 We tested the hypothesis that an objective measure of total daily activity, including both exercise and nonexercise physical activity, is associated with longevity in community-dwelling older persons.
We used clinical data from participants of the Memory and Aging Project, a longitudinal cohort study of aging.5 The study was approved by Rush University Medical Center institutional review board. Total daily physical activity (exercise and nonexercise physical activity) was measured at baseline for up to 10 days with actigraphs (Actical; Philips Healthcare) worn on the wrist 24 h/d.6 All participants underwent structured annual clinical examination as previously described.5
There were 893 participants, with a mean (SD) age of 82.0 (7.30) years and mean (SD) education of 14.8 (2.97) years; 76.3% were women; and 11.8% had clinical dementia. Total daily physical activity was measured for a mean (SD) of 9.3 (1.2) days. Total daily physical activity ranged from 0.06 × 105 counts/d to 13.56 × 105 counts/d (mean [SD]: 2.88 × 105 [1.57 × 105] counts/d).
During a mean follow-up of 4 years, there were 212 deaths (23.7% of cohort). In a Cox proportional hazards model adjusting for age, sex, and education, a higher level of total daily physical activity was associated with a decreased risk of death (hazard ratio [HR], 0.71; 95% CI, 0.63-0.79). Thus, an individual with high total daily physical activity (90th percentile) had approximately one-fourth the risk of death compared with an individual with low total daily physical activity (10th percentile).
In further sensitivity analyses, the association of total daily activity and death remained significant even after excluding (1) individuals with clinical dementia (HR, 0.77; 95% CI, 0.68-0.88); (2) cases with a history of stroke or Parkinson disease (HR, 0.73; 95% CI, 0.64-0.83); or (3) cases dying during the first 3 years of follow-up, leaving 79 incident cases of death (HR, 0.81; 95% CI, 0.68-0.97). Total daily physical activity was associated with death even after adjusting for several possible confounders including traditional self-reported physical activity and the frequency of other late-life social and cognitive activities, level of motor and cognitive function, chronic health conditions, and depressive symptoms alone (Table). The association between total daily activity and risk of death did not vary by age, sex, or education (results not shown). Although total daily activity was lower in persons with clinical dementia, the association of total daily activity and death did not vary by dementia status (total daily activity × dementia, HR, 0.89; 95% CI, 0.67-1.19).
A higher level of total daily physical activity, measured by actigraphy, in nearly 900 older community-dwelling individuals was associated with a reduced risk of death. Total daily physical activity captures aspects of physical activity not assessed by traditional physical activity measures and remained associated with risk of death even after adjusting for a wide range of late-life physical, cognitive, and social activities. Furthermore, the association between total daily physical activity and risk of death persisted after adjustment for possible confounders including motor and cognitive function and chronic health conditions did not vary with age, sex, education, or dementia status and persisted even after excluding persons dying during the first 3 years of follow-up. These data support the link between total daily physical activity and risk of death in very old persons and suggest that an active lifestyle including not only physical exercise but also nonexercise physical activities may augment health and longevity in old age.
Delineating the role of physical activity in older individuals is especially challenging, since older individuals are commonly affected by chronic health conditions, low fitness levels, and functional limitations that occur concomitantly with age-related loss of cognitive and motor function. Until recently, objective measures of physical activity could only be obtained in the laboratory setting, thereby excluding older, more debilitated individuals unable to participate in testing.1 Moreover, recent studies suggest that laboratory testing may not reflect the level and patterns of physical activity in the community setting.7 Furthermore, energy expenditure from nonexercise physical activities may have a substantial role when considering the benefits that accrue from physical activity.2,4 Thus, it may be particularly important to use techniques that measure both exercise and nonexercise activities to explicate the role of physical activity in older persons.8 The present study took advantage of recent technology that makes it feasible to collect quantitative measures of total daily physical activity for prolonged periods in the community setting with devices that are minimally intrusive and do not rely on participant recall. Findings from the present study underscore the potential benefits of higher levels of nonexercise physical activity as well as exercise and leisure activity.2- 4 Because older persons who have underlying health problems may not be able to engage in formal exercise, the option of increasing nonexercise physical activities may have important translational consequences for the design of physical activity intervention studies and public policy goals. Finally, these results lend support for efforts to encourage a more active lifestyle for all older adults even those with chronic health conditions and functional impairments.
This study has some limitations. While the findings were robust to potential confounding variables and sensitivity analyses, the potential for reverse causality cannot be excluded. Other limitations include the selected nature of the cohort, the self-reporting of chronic diseases, and the fact that certain types of activities may not have been measured owing to placement of the actigraphs on the wrist. Furthermore, the device used in the present study does not differentiate the types of activities that were performed.9 Additional studies are needed to determine the relative contributions of exercise and nonexercise physical activity in older individuals and the degree to which they can be independently modified to augment survival.8
Correspondence: Dr Buchman, Rush Alzheimer's Disease Center, Rush University Medical Center, Armour Academic Facility, 600 S Paulina St, Ste 1022, Chicago, IL 60612 (Aron_S_Buchman@rush.edu).
Author Contributions: Dr Buchman had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Buchman and Bennett. Acquisition of data: Buchman and Bennett. Analysis and interpretation of data: Buchman, Yu, Boyle, Shah, and Bennett. Drafting of the manuscript: Buchman. Critical revision of the manuscript for important intellectual content: Buchman, Yu, Boyle, Shah, and Bennett. Statistical analysis: Yu and Boyle. Obtained funding: Buchman and Bennett. Administrative, technical, and material support: Buchman and Bennett. Study supervision: Buchman and Bennett.
Financial Disclosure: None reported.
Funding/Support: The study was supported by National Institute on Aging grants R01AG17917, R01AG24480, and R01AG34374.
Additional Contributions: We are indebted to the participants and the staff of the Rush Memory and Aging Project and the Rush Alzheimer's Disease Center for this work.
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