Osteoarthritis and risk of mortality in the USA: a population-based cohort study

BACKGROUND: Osteoarthritis (OA) is the most common joint disease, but its association with mortality is unclear. METHODS: We analysed data on adult participants in the 1988–94 and 1999–2010 National Health and Nutrition Examination Surveys, followed for mortality through 2011. OA was defined by self-report, and in a subset of participants 60 years or older with knee X-rays, radiographic knee OA (RKOA) was defined as Kellgren–Lawrence score ≥2. Cox proportional hazards were used to determine the mortality hazard ratio (HR) associated with self-reported OA and RKOA, adjusting for covariates. RESULTS: The sample included 51 938 participants followed for a median 8.9 years; 2589 of them had knee X-rays and were followed for a median of 13.6 years. Self-reported OA and RKOA prevalences were 6.6% and 40.6%, respectively. Self-reported OA was not associated with mortality. RKOA was associated with an increased risk of mortality from cardiovascular diseases (CVD) {HR 1.43 [95% confidence interval (CI): 1.32, 1.64]}, diabetes [HR 2.04 (1.87, 2.23)] and renal diseases [HR 1.14 (1.04, 1.25)], but with a reduced risk of cancer mortality [HR 0.88 (0.80, 0.96)]. Participants with early RKOA onset (diagnosed before age 40) had a higher risk of mortality from all causes [HR 1.53 (1.43, 1.65)] and from diabetes [HR 7.18 (5.45, 9.45)]. Obese participants with RKOA were at increased risk of mortality from CVD [HR 1.89 (1.56, 2.29)] and from diabetes [HR: 3.42 (3.01, 3.88)]. CONCLUSIONS: Self-reported OA was not associated with mortality. RKOA was associated with higher CVD, diabetes and renal mortality, especially in people with early onset of the disease or with obesity.