The Association of Waist Circumference With Functional Mobility Among Adults With Obesity and Knee Osteoarthritis

PURPOSE: Knee osteoarthritis (OA) is the most common cause of functional limitation (Himes, 2000) such as difficulty with functional mobility (White, Niu, & Zhang, 2013). Obesity is a well-known risk factor for both knee OA (Himes, 2000) and functional mobility difficulties (Forhan & Gill, 2013; Gill & Narain, 2012). The presence of obesity in adults with knee OA engenders a vicious cycle wherein the development of difficulties with functional mobility restricts participation in activities of daily living, leading to reduced physical activity, increased weight gain, and potential worsening of knee OA. The distribution of body mass (i.e., waist circumference) may be linked with functional mobility difficulty above and beyond effects imposed by overall mass (i.e., obesity).

At present, the extent to which waist circumference is associated with decreased functional mobility independent of obesity is not known. The purpose of this study was to examine to what extent high waist circumference was linked with developing difficulty with walking speed and distance over 4 yr in adults with knee OA. We were particularly interested in walking speed and distance because these functional abilities may be the first to change noticeably if patients develop difficulty with functional mobility.

Both walking speed and endurance are important elements contributing to the ability to walk in the community. For instance, a speed of >1.2 meters per second (m/s) is the minimum speed necessary to cross a timed crosswalk (Langlois et al., 1997). Moreover, the ability to walk at least 400 m is associated with independence with walking in the community. Therefore, it may be beneficial for clinicians to monitor changes in speed and distance prior to clients with obesity and knee OA developing further difficulties.

DESIGN: This was a longitudinal study in which we examined a cohort of people ages 45–79 yr from the Osteoarthritis Initiative who have been followed annually for the development or progression of OA since the initial enrollment period in 2004.

METHOD: Using data from the Osteoarthritis Initiative, we employed World Health Organization categories for body mass index (BMI) and waist circumference (small–medium and large). Adults contributed baseline data on walking at a community distance (n = 3,460) and speed (n = 2,646) and were tested 4 yr later. Difficulty with speed was defined by slow gait: <1.2 m/s during a 20-m walk, and difficulty with distance was defined by an inability to walk 400 m. We calculated risk ratios (RRs) to examine the likelihood of developing difficulty with distance and speed using obesity and waist circumference as predictors, with RRs adjusted for potential confounders (i.e., age, sex, race, education, physical activity, and OA status).

RESULTS: Participants with obesity and large waist circumference were 2.2 times more likely to have difficulty with speed at 4 yr compared with participants with healthy weight and small–medium waist circumference (adjusted RR = 2.2, 95% confidence interval [CI] [1.6, 3.1], p < .0001). Those with obesity and small–medium waist circumference had no additional risk of developing speed difficulty at 4 yr compared to those with healthy weight and small–medium waist circumference (adjusted RR = 0.9, 95% CI [0.2, 3.7], p = .93). Participants with obesity and large waist circumference had 2.4 times the risk of developing the inability to walk 400 m compared with those with a healthy BMI and small–medium waist circumference (adjusted RR = 0.9, 95% CI [1.6, 3.7], p < .0001).

CONCLUSION: Waist circumference may be a main risk factor for developing difficulty with speed in adults with obesity and knee OA. These findings may suggest that measuring waist circumference in research and in clinical practice may be important to better stratify the risk of decreased functional mobility among adults with or at risk of knee OA.

References

Forhan, M., & Gill, S. V. (2013). Obesity, functional mobility, and quality of life. Best Practice and Research: Clinical Endocrinology and Metabolism, 27, 129–137. https://doi.org/10.1016/j.beem.2013.01.003

Gill, S. V., & Narain, A. (2012). Quantifying the effects of body mass index on safety: Reliability of a video coding procedure and utility of a rhythmic walking task. Archives of Physical Medicine and Rehabilitation, 93, 728–730. https://doi.org/10.1016/j.apmr.2011.09.012

Himes, C. L. (2000). Obesity, disease, and functional limitation in later life. Demography, 37, 73–82.

Langlois, J. A., Keyl, P. M., Guralnik, J. M., Foley, D. J., Marottoli, R. A., & Wallace, R. B. (1997). Characteristics of older pedestrians who have difficulty crossing the street. American Journal of Public Health, 87, 393–397.

White, D. K., Niu, J., & Zhang, Y. (2013). Is symptomatic knee osteoarthritis a risk factor for a trajectory of fast decline in gait speed? Results from a longitudinal cohort study. Arthritis Care and Research, 65, 187–194. https://doi.org/10.1002/acr.21816