摘要：Objectives. We examined whether objectively measured sedentary behavior is related to subsequent functional loss among community-dwelling adults with or at high risk for knee osteoarthritis. Methods. We analyzed longitudinal data (2008–2012) from 1659 Osteoarthritis Initiative participants aged 49 to 83 years in 4 cities. Baseline sedentary time was assessed by accelerometer monitoring. Functional loss (gait speed and chair stand testing) was regressed on baseline sedentary time and covariates (baseline function; socioeconomics [age, gender, race/ethnicity, income, education], health factors [obesity, depression, comorbidities, knee symptoms, knee osteoarthritis severity, prior knee injury, other lower extremity pain, smoking], and moderate-to-vigorous activity). Results. This cohort spent almost two thirds of their waking hours (average = 9.8 h) in sedentary behaviors. Sedentary time was significantly positively associated with subsequent functional loss in both gait speed (−1.66 ft/min decrease per 10% increment sedentary percentage waking hours) and chair stand rate (−0.75 repetitions/min decrease), controlling for covariates. Conclusions. Being less sedentary was related to less future decline in function, independent of time spent in moderate-to-vigorous activity. Both limiting sedentary activities and promoting physical activity in adults with knee osteoarthritis may be important in maintaining function. Knee osteoarthritis is a major cause of arthritis-related functional loss and disability. 1 The number of total knee replacement surgeries has soared 161.5% among Medicare participants over the past 20 years, a $5 billion annual tab that will continue to grow as baby boomers age 2 because an increasing number of adults will be at high risk for developing obesity-related knee osteoarthritis. 3,4 Nearly two thirds of obese adults are expected to develop knee osteoarthritis at some point in their lives. 5 Preservation of function in community-dwelling adults with and at high risk for knee osteoarthritis is critical to maintaining independence, quality of life, and contained medical costs in a population segment experiencing tremendous growth. 6 Osteoarthritis treatment options focus on exercise, self-efficacy, and analgesics. 7 However, the number of people with osteoarthritis meeting 2008 National Physical Activity Guidelines is exceedingly low. 8 Sedentary behaviors are defined as seated or reclining postures that require low levels of energy expenditure (e.g., < 1.5 metabolic equivalent units). 9 Inactivity physiology, emerging as an area of interest distinctly different from exercise physiology, has major implications for knee osteoarthritis development and treatment. Typically, adults spend one half of their waking time watching TV or in other sedentary activities. 10,11 Adults with knee osteoarthritis may spend even more time in sedentary behaviors. 8 These findings motivate the intriguing hypothesis that sedentary behaviors affect physical function independent of time spent in recommended moderate-to-vigorous activity among adults with or at risk for knee osteoarthritis. To our knowledge, only 1 longitudinal study has examined the relationship of sedentary behaviors to changes in physical function. 12 However, that study was limited to women; used self-reported measures of physical activity, which are subject to known bias 13 ; and did not investigate whether the relationship was independent of moderate- to vigorous-intensity physical activity. This study is a longitudinal cohort study that adds to the literature by evaluating the relationship of sedentary time objectively assessed from accelerometer monitoring to objectively measured changes in physical performance in community-dwelling adults with knee osteoarthritis or the presence of knee osteoarthritis risk factors, which elevates their risk for functional loss.
