Macronutrients intake in adulthood and risk of dementia in old age: a 20-years follow-up Italian study

Objectives: A high caloric intake has been associated with an increased risk of cognitive decline. Macronutrients are the main determinants of total caloric intake, thus aim of this study was to investigate the association between daily energy intake derived from carbohydrates, proteins and fats in relation to the risk of dementia. Materials and Methods: This is a prospective cohort study on a population of residents (n = 1604) in two districts of Northern Italy aged 40-74 years old who were examined about dietary habits and other lifestyles during the period 1991-5. Dietary habits were assessed by means of a 158-item food frequency questionnaire at baseline. Occurrence of Alzheimer' Disease (AD) and Vascular/other forms of Dementia (VaOD) were ascertained using Regional Health Registries. The proportion of daily energy intake (calories) derived from carbohydrates (%), proteins (%) and fats (%) was calculated and participants were ranked as "low" and "high" intake. Cox models were used to assess the associations between % macronutrients and incident AD and VaOD adjusting for potential confounders. Results: During a median of 18.6 years of followup, 73 incident dementia cases had occurred (39 AD and 34 VaOD). In the fully adjusted models the risk of AD was signifi cantly increased in people with high % carbohydrates (HR 2.45, 95%CI 1.08-5.57) but was reduced in those with high % fats (HR 0.34, 95%CI 0.16-0.71) and high % proteins (HR 0.78, 95%CI 0.38-1.60). The risk of VaOD was elevated in subjects with high % fats (HR 1.77, 0.79-3.95) but was decreased in persons with high % protein intake (HR 0.49, 95%CI 0.22-1.08) even though the estimates did not reach the signifi cance. No association with % carbohydrates was observed. Discussion: High % carbohydrates and low % proteins and fats were associated with an increased risk of AD whereas low % proteins and high % fats increased the risk of VaOD in our cohort. A possible explanation might reside in the food sources. Olive oil, rich in monounsaturated fatty acids, was the main source of fats in AD subjects. Persons who developed VaOD had a high intake of lard and margarine, rich in saturated and trans-unsaturated fatty acids. Regarding carbohydrates, subjects with AD had a higher intake of foods with high glycemic index than individuals with VaOD. Conclusion: Our data suggest that certain dietary choices and habits in adulthood can play a key role in the prevention of AD and dementia in old age.