• Dorothy D Dunlop, Jing Song, Jennifer M Hootman, Michael C Nevitt, Pamela A Semanik, Jungwha Lee, Leena Sharma, Charles B Eaton, Marc C Hochberg, Rebecca D Jackson, C Kent Kwoh, and Rowland W Chang.
• Department of Medicine, Northwestern University, Feinberg School of Medicine, Chicago, Illinois; Department of Preventive Medicine, Northwestern University, Feinberg School of Medicine, Chicago, Illinois. Electronic address: ddunlop@northwestern.edu.
• Am J Prev Med. 2019 May 1; 56 (5): 664672664-672.

IntroductionPhysical activity guidelines recommend minimum thresholds. This study sought to identify evidence-based thresholds to maintain disability-free status over 4years among adults with lower extremity joint symptoms.MethodsProspective multisite Osteoarthritis Initiative accelerometer monitoring cohort data from September 2008 through December 2014 were analyzed. Adults (n=1,564) aged ≥49years at elevated disability risk because of lower extremity joint symptoms were analyzed for biennial assessments of disability-free status from gait speed ≥1meter/second (mobility disability-free) and self-report of no limitations in activities of daily living (activities of daily living disability-free). Classification tree analyses conducted in 2017-2018 identified optimal thresholds across candidate activity intensities (sedentary, light, moderate-vigorous, total light and moderate-vigorous activity, and moderate-vigorous accrued in bouts lasting ≥10 minutes).ResultsMinimal thresholds of 56 and 55 moderate-vigorous minutes/week best predicted disability-free status over 4years from mobility and activities of daily living disabilities, respectively, across the candidate measures. Thresholds were consistent across sex, BMI, age, and knee osteoarthritis presence. Mobility disability onset was one eighth as frequent (3% vs 24%, RR=0.14, 95% CI=0.09, 0.20) and activities of daily living disability onset was almost half (12% vs 23%, RR=0.55, 95% CI=0.44, 0.70) among people above versus below the minimum threshold.ConclusionsAttaining an evidence-based threshold of approximately 1-hour moderate-vigorous activity/week significantly increased the likelihood of maintaining disability-free status over 4years. This minimum threshold tied to maintaining independent living abilities has value as an intermediate goal to motivate adults to take action towards the many health benefits of a physically active lifestyle.Copyright © 2019 American Journal of Preventive Medicine. All rights reserved.

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