BACKGROUND: Prior research has rarely explored the link between sleep duration trajectories and cardiovascular disease (CVD) either in cross-sectional or longitudinal data. OBJECTIVE: We aimed to analyze the relationship between sleep duration trajectories and the incidence of CVD. METHODS: Data from 5603 participants in the China Health and Retirement Longitudinal Study (CHARLS) were used in the analysis. Sleep duration was self-reported at multiple time points, and group-based trajectory modeling identified distinct patterns of total and nocturnal sleep duration over time. To investigate the link among sleep duration trajectories and CVD, Cox proportional hazards models, restricted cubic splines, and mediation analyses were used, with sensitivity analyses ensuring the results' robustness. RESULTS: Four sleep duration trajectories were identified, including steady high, inverted U-shaped, steady low, and U-shaped. In fully adjusted models, an inverted U-shaped sleep trajectory was associated with a 34% higher risk of hypertension compared with the steady high group (total sleep: hazard ratio [HR]=1.34, 95% CI 1.07-1.69; P=.01). Notably, the inverted U-shaped sleep trajectory showed a 110% increased stroke risk during nocturnal periods compared to the steady high group (nocturnal sleep: HR=2.10, 95% CI 1.08-4.05; P=.03). The findings remained consistent across a range of sensitivity analyses. Hypertension was identified as a partial mediator of the association between sleep instability and stroke risk. CONCLUSIONS: The findings indicate that an inverted U-shaped sleep pattern is associated with increased cardiovascular risk, partially mediated by hypertension, highlighting sleep stability as a potential preventive target.