Diet, lifestyle and chronic disease burden

Background Diet, Body Mass Index (BMI), physical activity and smoking are among the most important lifestyle factors that influence global disease burden. In this thesis we investigate the relations of these factors with total disease burden in a large Dutch population, the EPIC-NL cohort. In this cohort lifestyle data were collected between 1993-7 and participants were followed for diseases until December 31, 2007. We defined five different dietary patterns and we expressed disease burden in Disability-Adjusted Life Years (DALYs). DALYs are the sum of Years Lost due to Disability and the Years of Life Lost due to premature mortality. The advantage of this summary health measure is that in the outcome morbidity as well as mortality of several diseases are combined. Lifestyle factors that have small effects on several diseases will be more easily identified as important for public health. Furthermore, DALYs help estimating the overall effect habits that have opposing effects on different diseases. MethodsThe DALYs are estimated for 33,066 healthy men and women aged 20-70 years at recruitment into the EPIC-NL study. BMI, physical activity, diet and smoking are investigated separately and combined into a health behaviour score. We selected 5 dietary patterns that are relevant for the Dutch EPIC-NL population: 1. the Dutch guidelines for a healthy diet (Dutch Healthy Diet-index (DHD-index)), 2. the dietary guidelines proposed by the WHO (Healthy Diet Indicator (HDI)), 3. a Mediterranean Style Diet (modified Mediterranean Diet Score (mMDS)), and the a posteriori defined 4. prudent and 5. Western-type dietary pattern. ResultsOur study shows that never smoking, a BMI lower than 25, being physically active and consuming a healthy diet all result in a longer healthy life. Persons who adhere to all four healthy lifestyle factors live approximately two years longer in good health. Higher adherence to any of the studied dietary patterns with the exception for the Western dietary pattern is related to lower disease burden. Persons who reported at baseline stronger adherence to the mMDS or prudent dietary pattern lived on average 2 months longer in good health (per standard deviation increase in score). We find a more modest association between the HDI and the DHD-index and overall disease burden: per standard deviation higher adherence was associated with approximately 1 month longer in good health. ConclusionOur results show a beneficial impact on total disease burden when adhering to a healthy diet, specifically when adhering to a Mediterranean type of diet, including limited meat and meat products, plenty of fruit, nuts, fish and unsaturated fat and a limited amount of alcohol. Next to a healthy diet a combination of healthy lifestyle behaviours is important for a longer life in good health. Due to the underestimation of DALYs the estimates we reported should be considered the minimum estimate. Longer follow-up, a more complete assessment of disabilities and more insight in the impact of comorbidity of disability weights will give a more complete picture and a better insight into the association between lifestyle factors and disease burden.