Background/Purpose Declining physical function (PF) is a common consequence of osteoarthritis (OA), and poor PF is associated with death. It is possible that the resulting reduction in physical activity may increase an individual’s risk of development or progression of life-threatening chronic diseases such as CVD and diabetes; however, we previously found that individuals with severe knee and/or hip OA were more likely to die, independent of comorbidities. We therefore sought to explore whether poorer PF among those with OA was associated with death at subsequent follow-up, independent of comorbidities associated with reduced PF.

Methods Data were from 1,525 individuals aged 45 or older with radiographically confirmed (KL grade ≥2) knee and/or hip OA (rOA) who entered the cohort during the original study enrollment (1990-1997) and newly enrolled individuals recruited during the cohort enrichment (2003-2004). Vital status was assessed at first follow up period (1999-2004 for original participants; 2007-2010 for new enrolls). Severe rOA was defined as a KL grade ≥3; symptomatic OA (sxOA) was a subset of those with rOA and symptoms in the same joint. PF assessment was the 8-ft (2.4-m) walk test. Average number of steps needed to complete the walk and average times to the nearest tenth of a second across two trials were computed. Dichotomous variables based on medians were used for walk time (<3.4 sec and ≥3.4 sec) and number of steps (<5.5 steps and ≥5.5 steps). Multilevel logistic regression models controlling for the primary sampling unit (PSU) were used to estimate odds ratios (OR) and 95% confidence intervals (CI) for the associations between each PF measure at baseline and whether death occurred by the first follow-up evaluation. All models were adjusted for age, race, sex, BMI, smoking, depression, stroke, diabetes and CVD.

Results Our sample was mostly women (63%), Caucasian (67%) and had a mean age of 65 years. At first follow-up, 18% of our sample had died. Walking time and number of steps above their medians were associated with about a doubling in the odds of death among those with knee and/or hip rOA (Table 1). Similar associations were observed when restricted to individuals with sxOA, and slightly attenuated ORs among those with severe disease that failed to reach statistical significance, possibly due to a smaller sample size. The highest odds of death with greater walking times were seen among individuals who had hip rOA whether with knee rOA (OR=2.33; 95% CI=1.20-4.51) or without knee rOA (OR=2.40; 95% CI=1.25-4.61).

Conclusion Our findings suggest that poor PF among a cohort of individuals with knee and/or rOA is associated with death, findings which are independent of comorbidities linked to increased mortality. We observed associations with death were particularly strong for individuals with hip rOA, therefore suggesting a potential survival benefit through intervention among those individuals.