Knee osteoarthritis and time-to all-cause mortality in six community-based cohorts: an international meta-analysis of individual participant-level data.

BACKGROUND: Osteoarthritis (OA) is a chronic joint disease, with increasing global burden of disability and healthcare utilisation. Recent meta-analyses have shown a range of effects of OA on mortality, reflecting different OA definitions and study methods. We seek to overcome limitations introduced when using aggregate results by gathering individual participant-level data (IPD) from international observational studies and standardising methods to determine the association of knee OA with mortality in the general population. METHODS: Seven community-based cohorts were identified containing knee OA-related pain, radiographs, and time-to-mortality, six of which were available for analysis. A two-stage IPD meta-analysis framework was applied: (1) Cox proportional hazard models assessed time-to-mortality of participants with radiographic OA (ROA), OA-related pain (POA), and a combination of pain and ROA (PROA) against pain and ROA-free participants; (2) hazard ratios (HR) were then pooled using the Hartung-Knapp modification for random-effects meta-analysis. FINDINGS: 10,723 participants in six cohorts from four countries were included in the analyses. Multivariable models (adjusting for age, sex, race, BMI, smoking, alcohol consumption, cardiovascular disease, and diabetes) showed a pooled HR, compared to pain and ROA-free participants, of 1.03 (0.83, 1.28) for ROA, 1.35 (1.12, 1.63) for POA, and 1.37 (1.22, 1.54) for PROA. DISCUSSION: Participants with POA or PROA had a 35-37% increased association with reduced time-to-mortality, independent of confounders. ROA showed no association with mortality, suggesting that OA-related knee pain may be driving the association with time-to-mortality. FUNDING: Versus Arthritis Centre for Sport, Exercise and Osteoarthritis and Osteoarthritis Research Society International.

Obesity and the Relative Risk of Knee Replacement Surgery in Patients With Knee Osteoarthritis: A Prospective Cohort Study.

OBJECTIVE: It is unclear what impact obesity has on the progression of knee osteoarthritis (OA) from diagnosis to knee replacement surgery. This study was undertaken to examine the relative risk of knee replacement surgery in overweight and obese patients who were newly diagnosed as having knee OA in a community setting. METHODS: Subjects were selected from the Information System for Development of Primary Care Research database, which compiles comprehensive clinical information collected by health care professionals for >5.5 million people in Catalonia, Spain (80% of the population). Patients newly diagnosed as having knee OA in primary care between 2006 and 2011 were included. Knee replacement was ascertained using International Classification of Diseases, Ninth Revision, Clinical Modification codes from linked hospital admissions data. Multivariable Cox regression models were fitted for knee replacement according to body mass index (BMI), and were adjusted for relevant confounders. Population proportional attributable risk was calculated. RESULTS: A total of 105,189 participants were followed up for a median of 2.6 years (interquartile range 1.3-4.2). Of these patients, 7,512 (7.1%) underwent knee replacement. Adjusted hazard ratios and 95% confidence intervals (95% CIs) for knee replacement for the World Health Organization BMI categories were 1.41 (95% CI 1.27-1.57) for overweight, 1.97 (95% CI 1.78-2.18) for obese I, 2.39 (95% CI 2.15-2.67) for obese II, and 2.67 (95% CI 2.34-3.04) for obese III compared to normal weight. The effect of BMI on risk of knee replacement was stronger among younger participants. The population attributable risk of obesity for knee OA-related knee replacement was 31.0%. CONCLUSION: Overweight and obese patients are at >40% and 100% increased risk of knee replacement surgery, respectively, compared to patients with normal weight. This association is even stronger in younger patients. Weight reduction strategies could potentially reduce the need for knee replacement surgery by 31% among patients with knee OA.