Temporal relationship between osteoarthritis and comorbidities: a combined case control and cohort study in the UK primary care setting.

OBJECTIVE: To determine the burden of comorbidities in osteoarthritis (OA) and their temporal relationships in the UK. METHODS: The Clinical Practice Research Datalink (CPRD) GOLD was used to identify people with incident OA and age, gender and practice matched non-OA controls from UK primary care. Controls were assigned the same index date as matched cases (date of OA diagnosis). Associations between OA and 49 individual comorbidities and multimorbidity (≥2 comorbidities excluding OA) both before and after OA diagnosis were estimated, adjusting for covariates, using odds ratios (aOR) and hazard ratios (aHR) respectively. RESULTS: During 1997-2017, we identified 221 807 incident OA cases and 221 807 matched controls. Of 49 comorbidities examined, 38 were associated with OA both prior to, and following, the diagnosis of OA, and 2 (dementia and SLE) were associated with OA only following the diagnosis of OA. People with OA had higher risk of developing heart failure (aHR 1.63; 95% CI 1.56-1.71), dementia (aHR 1.62; 95% CI 1.56-1.68), liver diseases (aHR 1.51; 95% CI 1.37-1.67), irritable bowel syndrome (aHR 1.51; 95% CI 1.45-1.58), gastrointestinal bleeding (aHR 1.49; 95% CI 1.39-1.59), 10 musculoskeletal conditions and 25 other conditions following OA diagnosis. The aOR for multimorbidity prior to the index date was 1.71 (95% CI 1.69-1.74), whereas the aHR for multimorbidity after the index date was 1.29 (95% CI 1.28-1.30). CONCLUSIONS: People with OA are more likely to have other chronic conditions both before and after the OA diagnosis. Further study on shared aetiology and causality of these associations is needed.