Background/Purpose:

Regular physical activity has been demonstrated to improve quality of life for adults with chronic disease including osteoarthritis. Despite these benefits, half of adults with arthritis are inactive. An inactive lifestyle is associated with disability, loss of motion, pain, and stiffness. We analyzed longitudinal data from the Osteoarthritis Initiative (OAI) to evaluate the effect of transitioning from inactivity to activity on changes in function over a 2-year follow-up to assess the benefit of increasing physical activity in persons at high risk for disability.

Methods:

The Osteoarthritis Initiative enrolled adults who had or were at risk of developing knee osteoarthritis. Longitudinal physical activity accelerometer monitoring was conducted on a subgroup at baseline (48 month OAI visit) and at 2 years (72 month OAI visit). We evaluated two-year activity transitions on 565 individuals identified as being inactive at baseline (zero 10 minute bouts of moderate-to-vigorous [MV] intensity physical activity during a week). We examined the relationship of becoming active (that is, a transition from inactive to insufficient activity or inactive to meeting guideline levels [meeting DHHS Guidelines of at least 150 minutes/week MV activity]) versus remaining inactive in relationship to change in function as measured by gait speed, chair stand rate, and WOMAC function. Analyses used multiple regression analysis controlling for baseline modifiable factors (smoking, knee pain, depressive symptoms, and overweight/obesity), and descriptive factors (age, gender, race/ethnicity, education, income, arthritis severity as measured by K-L grade, knee injury, medical comorbidities, hip pain, foot or ankle pain, and chronic knee symptoms).

Results:

Of the 565 adults who were inactive at baseline, 141 (25%) became active (but insufficient to meet guidelines) while 15 (2.7%) became active enough to meet activity guidelines. Over two years, this group of adults characterized by baseline inactivity on average had worse function compared to baseline levels. However, people who became more active over two years compared to those who remained inactive lost less gait speed (2.6 versus 6.1 loss in feet/second), had improved chair stand (0.6 gain versus 1.0 loss repetitions/minute) and had less decrease in WOMAC function (0.7 versus 1.0 loss). This functional benefit remained after accounting for other modifiable and descriptive covariates. (See Table.)

Conclusion:

While this inactive group of individuals on average lost function over two years, those who increased their activity lost less function compared to those who remained inactive. Promoting increased physical activity, even to levels not meeting DHHS guidelines, may help inactive persons with arthritis minimize loss of function.