||Background The contribution of sufficient sleep duration to lower CVD risk in addition to sufficient physical activity, a healthy diet, (moderate) alcohol consumption, and non-smoking has not been investigated yet. Design The MORGEN study is a prospective cohort study including 8128 men and 9759 women aged 20-65 years, free of CVD at baseline. Methods Sufficient physical activity (3.5h/week cycling or sports), a healthy diet (Mediterranean Diet Score 5), (moderate) alcohol consumption (1 beverage/month), non-smoking, and sufficient sleep duration (7 hours) were assessed by self-administered questionnaires between 1994 and 1997. Cardiovascular morbidity and mortality were ascertained through linkage with national registers. Hazard ratios and preventable proportions were calculated adjusted for age, sex, and educational level. Results During 10-14 years of follow up, 607 composite CVD events (fatal CVD, nonfatal myocardial infarction and stroke) occurred, of which 129 were fatal. Those with the four traditional healthy lifestyle factors had a 57% lower risk of composite CVD (HR 0.43, 95% CI 0.31-0.59) and a 67% lower risk of fatal CVD (HR 0.33, 95% CI 0.16-0.68) compared with those with none or one healthy lifestyle factor. Sleeping sufficiently in addition to the four traditional lifestyle factors resulted in a 65% lower risk of composite CVD (HR 0.35, 95% CI 0.23-0.52), and an 83% lower risk of fatal CVD (HR 0.17, 95% CI 0.07-0.43). Conclusions Sufficient sleep and adherence to all four traditional healthy lifestyle factors was associated with lower CVD risk. When sufficient sleep duration was added to the traditional lifestyle factors, the risk of CVD was further reduced.