Epidemiology and risk factors of Alzheimer’s disease: A focus on diet

Abstract

Alzheimer’s disease (AD) appears to result from a highly dynamical, time-dependent cascade of neuropathological processes, which involve the balance between two antagonist pathways: an accumulation of lesions in the brain (evolving progressively over decades), balanced by a variety of cellular and tissular compensatory mechanisms. Preclinical research has indicated that several nutritional factors have the potential to modulate many components of this complex system; dietary interventions may thus constitute promising strategies for the prevention of AD. Extensive epidemiological research has been conducted on nutrition, diet, and AD dementia over the past two decades. This chapter reviews existing epidemiological literature on nutrition and cognitive aging and AD dementia, with a specific focus on observational, prospective studies, including both clinical outcomes and brain imaging biomarkers. Most studies investigated candidate foods and nutrients, including “good” fats (e.g., marine long-chain omega-3 polyunsaturated fatty acids provided by fish intake), antioxidant nutrients (i.e., vitamins C and E, carotenoids, and polyphenols, found in plant products), and B vitamins (e.g., folate provided by green leafy vegetables). Overall, associations between individual nutrients and both clinical outcomes and brain imaging biomarkers have been relatively inconsistent. Healthy dietary patterns such as the Mediterranean diet, which combine several healthy foods and nutrients, have been more consistently related to AD outcomes. Still, most randomized controlled trials on nutritional supplements for the prevention of AD have remained inconclusive so far. Future research should leverage innovative approaches such as “omics” methods to explore dietary exposures, novel imaging markers to capture prodromal AD, and longitudinal statistical approaches to model long-term trajectories of risk factors and AD markers, to better understand how and when diet may shape the brain and prevent AD.