BACKGROUND: Leisure activity and sleep time are key factors in cognitive impairment, but the impact of their long-term trajectories on incident cognitive impairment remains unclear. OBJECTIVE: To examine the association of leisure activity trajectories, sleep time trajectories and their combined effects with incident cognitive impairment in older adults. METHODS: Data from the Chinese Longitudinal Healthy Longevity Survey (2008-2018) were analyzed, including adults aged ≥65 who participated in at least three surveys. Group-based trajectory modeling explored leisure activity and sleep time patterns. Cox proportional-hazards regression model assessed the association of leisure activity trajectories and sleep time trajectories and their combined effects with incident cognitive impairment. RESULTS: We included 3094 participants with a median follow-up of 6.07 years. The optimal trajectory groups for leisure activity and sleep time were four and three, respectively. The low-level leisure activity group were associated with an increased risk of cognitive impairment (HR, 95%CI: 2.07, 1.37-3.13), whereas the high-level leisure activity group were associated with a reduced risk of cognitive impairment (HR, 95%CI: 0.60, 0.36-0.99). Short sleep time group was associated with a reduced risk of cognitive impairment (HR, 95%CI: 0.62, 0.41-0.92). In the combined effect, leisure activity belonging to the low-level group and sleep time belonging to the moderate sleep time group or the long sleep time group were associated with an increased risk of cognitive impairment. CONCLUSIONS: Long-term high-level leisure activity and short sleep time are associated with a reduced risk of cognitive impairment in older adults.