Work Productivity and Activity Impairment Across Functional Disability Levels in Patients with Inflammatory Arthritis

Objectives Inflammatory arthritis (IA) can progressively compromise physical function, leading to reductions in work productivity and daily activity. However, the thresholds at which productivity loss becomes clinically meaningful remain unclear, particularly across different IA types and within the Canadian healthcare context. This study quantified productivity and activity impairment across levels of functional disability to identify thresholds for intervention and inform early, function-preserving care strategies. Methods Data from the Rheum4U Precision Health Registry, including adults (> 18 years) with IA receiving care at a rheumatology clinic in Calgary/Canada, were analyzed. The first registry visit with complete Clinical Health Assessment Questionnaire (ClinHAQ) and the Work Productivity and Activity Impairment questionnaire (WPAI) was included. ClinHAQ scores categorized participants into minimal/no, mild, moderate, or severe disability. WPAI domains (absenteeism, presenteeism, overall work impairment, and activity impairment) were scored ranging 0-100%, with higher values indicating greater impairment. Kruskal-Wallis tests evaluated differences across disability levels, and Dunn’s post-hoc tests with Bonferroni correction identified pairwise differences. Results Among 1,337 participants (68% women; median age 52 [IQR 39-62] years), 59% had minimal/no disability, 18% mild, 21% moderate, and 2.5% severe functional disability. The median time since diagnosis was 7.2 [IQR 2.5-13.1] years. Significant differences were observed across all WPAI domains (p<0.001), with activity impairment showing the largest differences. Post-hoc analyses revealed that absenteeism, presenteeism, overall work impairment, and activity impairment increased progressively with functional disability, with the most consistent and statistically significant differences observed at moderate levels compared with minimal/no disability. Comparison involving mild disability also showed significant, though smaller, differences relative to minimal/no disability. Differences involving severe disability compared with minimal/no disability were generally smaller or non-significant, likely due to the small number of participants in this group. Activity impairment differed significantly across all disability levels, including comparisons involving severe disability. Conclusion In adults with IA, work productivity and activity impairment worsen progressively with increasing functional disability. Most notable productivity declines were detected at moderate ClinHAQ levels. These begin at mild disability but reach a clinically meaningful threshold once functional limitations are moderate. These results offer practical insights for early interventions aimed at preserving physical function. Implementing strategies when patients have minimal/no or mild disability may help maintain productivity and support patients’ participation in daily and work-related activities.