The Association of an Increasing Waist Circumference and Risk of Incident Low Physical Function in Adults with Knee Osteoarthritis

Objective. To investigate an 8-year change in waist circumference (WC) with the risk of incident low physical function over 1 year in adults with, or at risk of, knee osteoarthritis (OA). Methods. Data from the Osteoarthritis Initiative were used. Change in WC was measured from study enrollment (0 month) to the 96-month visit and classified as Increase (>= 5cm gain) or Maintain (< 5cm gain). We identified World Health Organization ( WHO) risk category based on WC at study enrollment as Large WC (males >= 102 cm, females >= 88 cm) or Small WC (males < 102 cm, females < 88 cm). The outcome was incident low physical function (>= 28 Western Ontario and McMaster Universities Osteoarthritis Index physical function subscale) at the 108-month visit. To investigate the association of the 8-year change in WC with the risk of low physical function, we calculated risk ratios (95% CI) and adjusted for potential confounders. We repeated the analyses stratified by the WHO disease risk category. Results. The Increase WC group had 1.43 (95% CI 1.04-1.96) times the risk of incident low physical function compared to adults in the Maintain WC group. Adults with a Large WC at baseline who increased WC had 1.55 (95% CI 1.00-2.37) times the risk of incident low physical function compared to those who maintained WC. Adults with a Small WC at baseline who increased WC had 1.97 (95% CI 0.84-4.63) times the risk compared to those who maintained WC. Conclusion. Increasing WC increases the risk of incident low physical function in the following year. Maintaining WC may mitigate developing low physical function.