Objective. To identify 24-hour activity-sleep profiles in adults with arthritis and explore factors associated with profile membership. Methods. Our study comprised a cross-sectional cohort and used baseline data from 2 randomized trials studying activity counseling for people with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), or knee osteoarthritis (OA). Participants wore activity monitors for 1 week and completed surveys for demographic information, mood (Patient Health Questionnaire 9), and sitting and walking habits (Self-Reported Habit Index). A total of 1,440 minutes/day were stratified into minutes off body (activity unknown), sleeping, resting, nonambulatory, and intermittent or purposeful ambulation. Latent class analysis determined cluster numbers; baseline-category multinomial logit regression identified factors associated with cluster membership. Results. Our cohort included 172 individuals, including 51% with RA, 30% with OA, and 19% with SLE. We identified 4 activity-sleep profiles (clusters) that were characterized primarily by differences in time in nonambulatory activity: high sitters (6.9 hours sleep, 1.6 hours rest, 13.2 hours nonambulatory activity, and 1.6 hours intermittent and 0.3 hours purposeful walking), low sleepers (6.5 hours sleep, 1.2 hours rest, 12.2 hours nonambulatory activity, and 3.3 hours intermittent and 0.6 hours purposeful walking), high sleepers (8.4 hours sleep, 1.9 hours rest, 10.4 hours nonambulatory activity, and 2.5 hours intermittent and 0.3 hours purposeful walking), and balanced activity (7.4 hours sleep, 1.5 hours sleep, 9.4 hours nonambulatory activity, and 4.4 hours intermittent and 0.8 hours purposeful walking). Younger age (odds ratio [OR] 0.95 [95% confidence interval (95% CI) 0.91-0.99]), weaker occupational sitting habit (OR 0.55 [95% CI 0.41-0.76]), and stronger walking outside habit (OR 1.43 [95% CI 1.06-1.91]) were each associated with balanced activity relative to high sitters. Conclusion. Meaningful subgroups were identified based on 24-hour activity-sleep patterns. Tailoring interventions based on 24-hour activity-sleep profiles may be indicated, particularly in adults with stronger habitual sitting or weaker walking behaviors. INTRODUCTION Adults with arthritis may not be able to spend much time in higher intensity physical activities due to activity limitations (1). Consequently, they may not be able to meet the aerobic activity guideline of getting at least 2.5 hours of moderate-to-vigorous physical activity (MVPA) every week (2-5). Arthritis-related pain, fatigue, limited joint and muscle function, or mood disruption may contribute to increased sedentary activity and less walking or impact sleep quality and quantity (1,6-8). Such pain may, in turn, have implications for a person's overall health, as being physically inactive and having insufficient (<6 hours) or excessive (>9 hours) sleep are independently associated with higher risk of all-cause mortality (8-14), including in people with arthritis (15). Supporting someone to be ph...