All models adjusted for baseline sedentary measure, age, sex, clinical site, and accelerometer wear time. Error bars indicate 95% CIs of the predicted mean.
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Wanigatunga AA, Ambrosius WT, Rejeski WJ, et al. Association Between Structured Physical Activity and Sedentary Time in Older Adults. JAMA. 2017;318(3):297–299. doi:10.1001/jama.2017.7203
Excessive sedentary time is associated with myriad negative health consequences, regardless of exercise participation,1 especially in older adults who accumulate the most sedentary volumes and have the highest risk of comorbidities.2,3 Furthermore, accumulating sedentary time in prolonged bouts (eg, binge television watching) exacerbates these deleterious effects.4 Although behavioral interventions can increase moderate-intensity activity, the transfer to sedentary behaviors remains unclear.
Institutional review boards at all sites approved the study protocol. Written informed consent was obtained from all participants. This study was a post hoc exploratory analysis of the Lifestyle Interventions and Independence for Elders (LIFE) study, a blinded randomized clinical trial conducted in 8 US centers between February 2010 and December 2013 (protocol for exploratory analysis is available in the Supplement). A moderate-intensity physical activity intervention (PA group) with a goal of 150 minutes per week of walking, in addition to strength, flexibility, and balance training, compared with a health education program (HE group) focused on elderly health, reduced the risk of major mobility disability in adults aged 70 to 89 years with mobility impairments.5 The PA group primarily focused on increasing overall activity levels; it did not specifically target reducing sedentary behaviors such as television viewing.
Participants were instructed to wear an accelerometer on the hip for 7 consecutive days during waking hours at baseline and 6, 12, and 24 months after randomization.6 Total sedentary time was defined as minutes registering fewer than 100 activity counts per minute per waking day. Total sedentary time was divided into bout lengths of 10 minutes or more, 30 minutes or more, and 60 minutes or more—each overlapping bout length represents a consecutively smaller segment of total sedentary time because longer bouts are less frequently observed. Mean differences in sedentary outcomes were estimated using linear mixed-effects modeling using the intention-to-treat approach in which participants were grouped according to randomization assignment. An α of .05 and 2-tailed alternative hypothesis testing was used for models adjusted for baseline sedentary value, age, sex, clinical site, and accelerometer wear time. Missing values were treated as missing completely at random. Accelerometer data were processed using R (R Foundation), version 3.4.0, and statistical analyses were performed using STATA (StataCorp), version 13.
Of the 1635 participants, 1341 had valid accelerometer data at baseline (≥10 hours/d for ≥3 days), 669 in the PA group and 672 in the HE group. Over 24 months, 1271 had at least 1 follow-up assessment and 1164 participants had data collected at the 24-month visit. Mean age was 79 years, 67% were women, 76% were non-Hispanic white, mean body mass index (calculated as weight in kilograms divided by height in meters squared) was 30, and 42% had a walking speed less than 0.8 m/s.
At baseline, participants wore the accelerometer for a mean of 870 minutes per day, spending 647 minutes per day in total daily sedentary time (Figure). At 6 months, the PA group accrued 630 total sedentary minutes per day and the HE group accrued 639 total sedentary minutes per day (group difference, −9 minutes [95% CI, −14 to −3]; P = .002). This difference persisted over the following 18 months (intervention × time interaction P = .61), although both groups became increasingly sedentary.
At baseline, participants spent a mean of 488 minutes per day in sedentary bouts of 10 minutes or more; 296 minutes per day in sedentary bouts of 30 minutes or more, and 145 minutes per day in sedentary bouts of 60 minutes or more (Figure). At 6 months, the PA group accumulated less sedentary time than the HE group in bouts of 10 minutes or more (475 minutes in the PA group vs 487 minutes in the HE group; group difference, −12 minutes [95% CI, −19 to −4]; P = .003) and bouts of 30 minutes or more (290 minutes in the PA group vs 299 minutes in the HE group; group difference, −9 minutes [95% CI, −17 to −1]; P = .02). Intervention differences were maintained over 24 months (intervention × time interaction P > .37 for both). No intervention differences were detected for bouts of 60 minutes or more. Both groups became increasingly sedentary across all bouts.
In older adults with mobility impairments, long-term, moderate-intensity physical activity was associated with a small reduction in total sedentary time, reflected in shorter bout lengths. Limitations include the inability to detect posture, napping, behavior types (eg, television watching), and whether changes in sedentary time were clinically meaningful. Overall, traditional approaches to increasing moderate-intensity physical activity have little transfer to reductions in total sedentary time and no transfer to prolonged bouts lasting an hour or longer. Additional behavioral approaches are needed to target and reduce sedentary behaviors.
Accepted for Publication: May 19, 2017.
Corresponding Author: Todd M. Manini, PhD, Department of Aging and Geriatric Research, University of Florida, 2004 Mowry Rd, Gainesville, FL 32610 (firstname.lastname@example.org).
Author Contributions: Drs Wanigatunga and Manini had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Wanigatunga, Rejeski, Gill, Glynn, Manini.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Wanigatunga, Ambrosius, Manini.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Wanigatunga, Ambrosius, Manini.
Obtained funding: Rejeski.
Administrative, technical, or material support: Wanigatunga, Glynn, Manini.
Supervision: Rejeski, Tudor-Locke, Manini.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Funding/Support: This research was supported by grant U01AG22376 from the National Institutes of Health (NIH) and the National Institute on Aging (NIA); supplement 3U01AG022376-05A2S from the National Heart, Lung, and Blood Institute (NHLBI); sponsored in part by the Intramural Research Program; and supported by grants T32AG000247, T32AG020499, P30AG028740 from the NIH and NIA (Dr Wanigatunga), and grants R01AG042525 and R01HL121023 (Dr Manini) and P30AG21342 and K07AG043587 (Dr Gill) all from the NIH.
Role of the Funder/Sponsor: The NIH, NIA, NHLBI, and the Claude D. Pepper Older Americans Independence Center had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and the decision to submit the manuscript for publication.
Additional Contributions: We thank Abby C. King, PhD (Stanford University), Jack M. Guralnik, MD, PhD, MPH (University of Maryland), Mary M. McDermott, MD (Northwestern University), Roger A. Fielding, PhD (Tufts University), and Marco Pahor, MD (University of Florida), for their important contributions toward the interpretation of the data and revisions to the article. All were funded as part of the LIFE trial.
Additional Information: The LIFE research group is listed in the references.5
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