Trajectories of sleep characteristics and incident cardiovascular disease

While sleep characteristics have been associated with cardiovascular disease (CVD), most studies have focused on single timepoints or isolated aspects. The prognostic value of broader, long-term sleep patterns remains unclear. We used data from 24,223 participants in the Swedish Longitudinal Occupational Survey of Health (SLOSH), with biennial follow-up between 2010 and 2018. Sleep characteristics were assessed via self-report and incident cardiovascular outcomes were identified through linkage to national registers. Cox proportional hazards models estimated associations between sleep variables and incident cardiovascular disease, and mixed-effects models assessed sleep trajectories. During follow-up, 1,687 developed cardiovascular outcomes. Nighttime insomnia was not associated with increased CVD risk unless accompanied by daytime symptoms (HR 1.22, 95 % CI 1.03-1.44; reference: no insomnia and no daytime symptoms). Similarly, long sleep duration (>8 h) was associated with higher risk only when combined with daytime symptoms (HR 1.35, 95 % CI 1.13-1.61; reference: 6-8 h of sleep and no daytime symptoms). Trajectory analyses showed that participants with long sleep at baseline who later developed CVD had a gradual increase in sleep duration over time (β for CVD >8 h × time = 0.06, 95 % CI 0.04-0.07; β × time² = -0.005, 95 % CI -0.01 to 0.00), while long sleepers who remained free of CVD showed stable or declining patterns. Daytime symptoms, particularly when accompanied by prolonged or increasing sleep, may reflect early physiological changes preceding cardiovascular disease. These findings highlight the importance of considering sleep patterns and changes over time rather than static measures alone.