Healthy aging through a healthy diet : never too old to eat healthy?!

Abstract Background: The world’s population is aging and with it the prevalence of chronic diseases, especially cardiovascular diseases and cancer, increases. A long lasting life is envisaged without the burden of disease. Therefore, current research focuses on risk factors, such as a healthy diet, which may decrease the occurrence of chronic diseases even at advanced age. Earlier studies, examining the role of a healthy diet in the elderly, applied different analysis strategies. In consequence, comparability across studies is limited and prevent an overall conclusion on the role of a healthy diet in elderly. Methods and subjects: Eleven prospective cohort studies among elderly people (N=396,391) from Europe and the United States, collaborating in the CHANCES consortium, were analysed. Most cohorts eligible for our analysis, assessed diet once at baseline. Therefore, we first assessed the stability of dietary patterns, derived with reduced rank regression (RRR), in the Zutphen Elderly Study. In the remainder of this thesis, healthy diets were defined based on the 2003 World Health Organization (WHO) “nutrient intake goals” and the 2007 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) food group recommendations. The recommendations were operationalized, using the Healthy Diet Indicator (HDI) and the WCRF/AICR diet score. The association between a healthy diet and risk of all-cause mortality and CVD mortality, was studied using the WHO recommendations, which aim at the prevention of chronic diseases in general. The cancer specific WCRF/AICR recommendations were applied to study the association between a healthy diet and cancer risk. Diet disease associations were assessed in each cohort separately, using Cox-proportional hazards regression. Cohort specific hazard ratios (HR) were pooled by random effects meta-analysis. Results: The results of the Zutphen Elderly Study showed that dietary patterns, derived by RRR, remained stable over a period of five years. In the CHANCES project a total of 84,978 person years were accumulated, during a median follow-up time ranging between 7 and 15 years across cohorts. An increase of 10 HDI points (range total score 0 to 70 points) was significantly associated with a decreased risk of all-cause mortality (HR: 0.90 and 95% confidence interval (CI): 0.87-0.93). The HR estimate was equivalent to a two year increase in life expectancy. We found a significant inverse association between an increase of 10 HDI points and CVD mortality for Southern European countries and the US (HR: 0.85, 95 % CI: 0.83-0.87), whereas no significant association was found for Northern and Central and Eastern Europe. An increase of 1 point for the WCRF/AICR diet score (range 0-4) was associated with a significantly 6% decreased risk in developing any type of cancer. Greatest risk reduction was found between a 1 point increase in WCRF/AICR diet score and colorectal cancer (HR: 0.84, 95% CI:0.80-0.89). Conclusion: Dietary indices based on globally defined dietary recommendations by WHO and WCRF/AICR were found to be associated with all-cause and CVD mortality and cancer risk in old age. Public health interventions targeted on the elderly should not focus on one definition of a “healthy diet” but rather a smart combination of available evidence, to optimally account for CVD as well as cancer specific outcomes.