Background/Purpose: A large waist circumference (WC) is associated with walking difficulty in people with or at risk for knee osteoarthritis (OA). To date, it is unclear whether a meaningful increase in WC is also associated with walking difficulty and poor health. This is important to study since minimizing gains in WC may be important to reduce functional limitation and low health-related quality of life (HRQoL), which are common in knee OA. The purpose of this study was to investigate the association of increasing WC with function and HRQoL in people with or at risk for knee OA.

Methods: Data was extracted from the Osteoarthritis Initiative, a large prospective cohort study of people with or at risk for knee OA. Our primary exposures of interest were baseline WC and a meaningful increase in WC. WC was measured around the participant’s mid torso at the largest circumference with a tape measure. Baseline WC was classified into two groups using established thresholds: 1) Large WC (males > 102cm, females > 88cm) and 2) Small WC (males ≤ 102cm, females ≤ 88cm). A meaningful increase in WC over an 8-year timeframe was classified into two groups: 1) Increase (> 5cm) and 2) Maintain (≤ 5cm). Our two outcome measures of interest were function and HRQoL at the 8-year follow up measured by 1) gait speed (m/s) during a 20-meter walk test and 2) Short Form 12 Physical Summary Scale (SF12-P). Gait speed < 1.2 m/s and a SF12-P < 40 indicated functional limitation and poor HRQoL, respectively. We calculated risk ratios and 95% confidence intervals RR(95%CI) to examine the association of increased WC with study outcomes, adjusted for potential confounders.

Results: Of 4796 participants with baseline WC data (58% female, age 61± 9, BMI 28.6 ± 4.8), 2543 and 2238 people were free of the outcome at baseline and had 8-year follow up data for SF12-P and gait speed, respectively. The Large WC-Increase group had the greatest risk of developing functional limitation and poor HRQoL compared with the Small WC-Maintain group (Table 1). Those in the Large WC-Maintain group had a greater risk of developing a functional limitation compared with the Small WC-Maintain group, but were at similar risk for poor HRQoL (Table 1). Participants in the Small WC-Increase group were at similar risk as the Small WC-Maintain group for developing functional limitation and poor HRQoL (Table 1).

Conclusion: People with large WC had greater risk of functional limitation and poor HRQoL 8 years later, irrespective of increasing WC, compared with those with a small WC. Those with a large WC who increase WC had the highest risk compared to those with a small WC who maintained WC. Educating people with knee OA to avoid WC gains, particularly those already with a large WC, may mitigate future functional limitation and poor HRQoL.