Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Physical Activity Assessed by Accelerometry in Persons with Knee OA Compared to National Guidelines: The Osteoarthritis Initiative (OAI).

Dunlop6,  Dorothy D., Song5,  Jing, Semanik8,  Pamela, Sharma5,  Leena, Chang4,  Rowland W., Bathon3,  Joan M., Eaton1,  Charles

Brown University
Univ of Pittsburgh, Pittsburgh, PA
University of Maryland, Baltimore, MD
Centers for Disease Control, Kennesaw, GA
Johns Hopkins Univ Ste, Baltimore, MD
Northwestern Univ, Chicago, IL
Northwestern University, Chicago, IL
Northwestern University Medical School, Chicago, IL
Ohio State University
Rehabilitation Institute of Chicago, Chicago, IL
UCSF, San Francisco, CA

Purpose:

Knee osteoarthritis (OA) is the most prevalent form of arthritis in the US. OA clinical practice guidelines identify a substantial therapeutic role for physical activity. However, we lack objective evidence on the physical activity experience of this population. Reports of physical activity in OA populations are largely based on self-report, which can overestimate activity time and intensity. This study uses accelerometers to objectively assess physical activity intensity and duration from a national knee OA cohort.

Methods:

Physical activity was measured via accelerometers at the year 4 clinic visit on 1056 participants in the OAI with baseline radiographic knee OA (KL grade >=2), Of these, 1021 (97%) had 4–7 valid days of accelerometer monitoring. Activity intensity was determined from accelerometer count cutpoints: light (<=2019), moderate (2020– 5998), vigorous (>=5999). Time spent in bouts lasting>=10 minutes of moderate-to-vigorous physical activity (MVPA) was determined. Gender differences in median intensity times were compared using quantile regression. Attainment of Centers for Disease Control and Prevention (CDC) guidelines for arthritis populations (>=150 bouted MVPA minutes/week) was assessed.

Results:

Persons with knee OA primarily engaged in light intensity activity and no measurable activity during a large portion of the day (Table). Overall, a median of only 9.9 minutes/day was spent in moderate-to-vigorous (MVPA) activity; less than 20% (1.4 minutes) of this time was done in bouts lasting more than 10 minutes. Men with knee OA had more minutes of no activity than women. However, men also had more MVPA minutes than women. These differences persisted after controlling for age and BMI. Recommended CDC physical activity guidelines were attained by only 18% of men and 10% of women.

Table. Median daily minutes of physical activity intensity among n=1021 persons with radiographic knee OA

Unadjusted ResultsnMinutes No activity (0 counts) MedianMinutes Light PA (1-2019 counts) MedianMinutes MVPA(>=2020 counts) MedianMinutes Any activity (>0 counts) Median
Men469429.6433.915.9458.0
Women552395.0478.07.3490.3
Men vs WomenDifference (95% CI)34.6(22.0, 47.2)-44.1(-58.2, -30.1)8.6(6.1, 11.1)-32.3(-46.5, -18.1)
Adjusted for Age, BMI, Race     
Men469432.1438.914.7457.0
Women552402.4490.76.9499.4
Men vs. WomenDifference (95% CI)32.9(17.3, 48.5)-42.7(-55.3, -30.1)5.4(3.3, 7.5)-36.9(-51.6, -22.1)

Conclusion:

Despite substantial health benefits from physical activity, persons with knee OA were particularly inactive. Physical activity guideline attainment among persons with knee OA based on accelerometry was under half the proportion previously reported based on self-reported activity, underscoring the importance of objective measures for accurate assessments. Although men were more likely than women to meet recommended physical activity guidelines they were also more likely to be inactive. These findings point to the importance of public health efforts to increase physical activity among persons with knee OA.

To cite this abstract, please use the following information:
Dunlop, Dorothy D., Song, Jing, Semanik, Pamela, Sharma, Leena, Chang, Rowland W., Bathon, Joan M., et al; Physical Activity Assessed by Accelerometry in Persons with Knee OA Compared to National Guidelines: The Osteoarthritis Initiative (OAI). [abstract]. Arthritis Rheum 2010;62 Suppl 10 :2096
DOI: 10.1002/art.29861

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