Trajectories of future sickness absence and disability pension days among individuals with a new sickness absence spell due to osteoarthritis diagnosis ≥21 days: a prospective cohort study with 13-month follow-up

INTRODUCTION: Osteoarthritis is one of the most common types of musculoskeletal diagnoses also among working-age populations, and often leads to long-term sickness absence (SA) spells or even disability pension (DP). THE AIM: was to identify future trajectories of days of SA and/or DP among people with a new SA spell due to osteoarthritis that became ≥21 long, and to investigate sociodemographic and morbidity characteristics of individuals in identified trajectories. METHODS: This is a prospective population-based cohort study using data from several Swedish registers. We studied future SA/DP among all 4894 individuals aged 16–64 years who, during the first 6 months of 2010, had an incident SA spell due to osteoarthritis (ICD-10 codes M15-19) ≥21 days. Using group-based trajectory modelling, we identified trajectories of mean SA/DP net days/month and 95% CIs for the 13 months from the 21st day of the index SA spell. Sociodemographic and morbidity characteristics were compared by χ(2) tests and multinomial logistic regression. RESULTS: We identified five trajectories of SA/DP days: ‘fast decrease’ (36% of the cohort), ‘medium fast decrease’ (29%), ‘slow decrease’ (15%), ‘fluctuating’ (12%) and ‘late decrease’ (8%). Individuals in the two trajectories who still had SA/DP days at end of follow-up (late decrease and fluctuating) were more likely to be older, born outside the EU and have indicators of more severe morbidity than those in the other trajectories. CONCLUSION: Five trajectories of future SA/DP days were identified; 80% of the cohort belonged to trajectories with no SA/DP by the end of follow-up. Identifying trajectories of future SA/DP provides new insights regarding the developments of SA/DP over time among people on SA due to osteoarthritis; not only days in the initial SA spell but also in new spells during follow-up need to be included for a better understanding.