Lifestyle factors and risk of cardiovascular diseases

Background Evidence is accumulating that lifestyle factors influence the incidence of fatal and non-fatal cardiovascular diseases (CVD). A healthy diet, being physically active, moderate alcohol consumption and not smoking are associated with a lower CVD risk. In addition to these lifestyle factors, recent research suggests that poor sleep may also be a risk factor of CVD. In this thesis, we focussed on a Mediterranean style diet, specific leisure time physical activities, and sleep duration and quality as risk factors for CVD. Methods Our analyses are based on the prospective Doetinchem Cohort Study (N ~ 3 400), the Monitoring Project on Risk Factors for Chronic Diseases (MORGEN) Study (N ~ 20 400) and the Dutch contribution to the European Prospective Investigation into Cancer and Nutrition (EPIC-NL) (N ~ 34 700). These studies included men and women aged 20-65 years when examined between 1993 and 1997. Diet was assessed with the validated EPIC food frequency questionnaire and operationalized with the Mediterranean Diet Score (MDS, range: 0-9). Physical activity was estimated with the validated EPIC physical activity questionnaire, with an emphasis on different leisure time activities. In addition, information was collected on duration and quality of sleep by two questions. Cardiovascular morbidity and mortality were ascertained through linkage with national registers. Multivariable Cox models were used to estimate the strength of the associations and 95% confidence intervals. Results During 12 years of follow-up, 206 CVD cases occurred in the Doetinchem Cohort Study, 1 486 cases in the MORGEN Study and 4 881 cases in the EPIC-NL Study. In the study on diet, a two unit increment in MDS was associated with a 22% lower risk of fatal CVD, and a 5% lower risk of total CVD. For specific CVDs, a 14% lower risk of myocardial infarction, a 12% lower risk of stroke, and a 26% lower risk of pulmonary embolism was observed. The MDS was not related to incident angina pectoris, transient ischemic attack and peripheral arterial disease. The use of multiple measurements of the MDS increased the strength of the associations with CVD and narrowed the confidence intervals. For leisure time physical activity, we showed that cycling was associated with an 18% lower risk of total CVD, sports with a 26% lower risk, and those who both cycled and performed sports had a 34% lower risk. Walking and gardening were not associated with CVD risk. Short sleep duration was associated with a 15% higher risk of total CVD, whereas long sleep duration and sleep quality separately were not associated. Short sleepers with a poor sleep quality had a 63% higher risk of total CVD compared to those with a normal sleep duration and good sleep quality. Finally, the combination of a healthy diet, sufficient physical activity, moderate alcohol consumption and non-smoking was associated with a 57% lower risk of composite CVD and a 67% lower risk of fatal CVD. The addition of sufficient sleep duration to these four traditional healthy lifestyle factors resulted in a 65% lower risk of composite CVD and an 83% lower risk of fatal CVD. Conclusions In this thesis, we showed that the strength of the association between dietary patterns and CVD incidence is likely underestimated because most studies used only the baseline measurement of diet. Furthermore, leisure time physical activities should be of at least moderate intensity to contribute to lower CVD risk. We also observed that sufficient sleep is a factor that should be taken into consideration in the prevention of CVD, in combination with a healthy diet, sufficient physical activity, moderate alcohol consumption and not smoking. Our results underscore the importance of a healthy lifestyle for CVD prevention.