Health status of individuals referred to first-line intervention for hip and knee osteoarthritis compared with the general population: an observational register-based study

OBJECTIVES: To describe the prevalence of comorbidities in a population referred to standardised first-line intervention (patient education and exercise) for hip and knee osteoarthritis (OA), in comparison with the general population. Furthermore, we aimed to evaluate if eventual differences were associated with socioeconomic inequalities. DESIGN: Register-based study. SETTING: Primary healthcare, Sweden. PARTICIPANTS: Individuals with hip and/or knee OA included in the Better Management for Patients with Osteoarthritis Register between 2008 and 2016 and and an age-matched, sex-matched and residence-matched reference cohort (1:3) from the general Swedish population. OUTCOME MEASURES: Comorbidities were identified with the RxRisk Index, the Elixhauser Comorbidity Index and the Charlson Comorbidity Index, and presented with descriptive statistics as (1) individual diseases, (2) disease categories and (3) scores for each index. The prevalence of comorbidities in the two populations was tested using logistic regression, with separate analyses for age groups and the most affected joint. We then adjusted the analyses for socioeconomic status. RESULTS: In this OA population, 85% had ≥1 comorbidity compared with 78% of the reference cohort (OR; 1.62 (95% CI 1.59 to 1.66)). Cardiovascular/blood diseases were the most common comorbidities in both populations (OA, 59%; reference, 54%), with OR; 1.22 (95% CI 1.20 to 1.24) for the OA population. Younger individuals with OA were more comorbid than their matched references overall, and population differences decreased with age (eg, ≥3 comorbidities, aged ≤45 years OR; 1.74 (95% CI 1.52 to 1.98), ≥81 years OR; 0.95 (95% CI 0.87 to 1.04)). Individuals with knee OA were more comorbid than those with hip OA overall. Adjustment for socioeconomic status did not change the estimates. CONCLUSION: Comorbidities were more common among individuals with hip and knee OA than among matched references from the general population. The differences could not be explained by socioeconomic status. TRIAL REGISTRATION NUMBER: NCT03438630.