Macronutrient Intake and Risk of Dementia in Community-Dwelling Older Adults: A Nine-Year Follow-Up Cohort Study

Background: Little is known about the association between macronutrient intake and incident dementia. Objective: To identify an optimal range of macronutrient intake associated with reduced risk of dementia. Methods: Our analysis included 93,389 adults aged 60–75 years from the UK Biobank. Diet was assessed using a web-based 24-h recall questionnaire between 2009–2012. Dementia was ascertained using hospital inpatient, death records, and self-reported data up to January 2021. We calculated a macronutrient score based on associations between an individual’s macronutrient intake and incident dementia. Results: During a median follow-up of 8.7 years, 1,171 incident dementia cases were documented. We found U-shape relationships for carbohydrate, fat, and protein intake with incident dementia. Compared to individuals with optimal carbohydrate intake, those with high intake (HR (95%CI): 1.48(1.15–1.91)) but not low intake (1.19(0.89–1.57)) had a higher risk of dementia. In the multivariable analysis, a low-fat intake (HR (95%CI): 1.42(1.11–1.82)) was associated with a higher risk of all-cause dementia. After adjustment for covariates, a high (HR (95%CI): 1.41(1.09–1.83)) but not low protein intake (1.22(0.94–1.57)) was associated with an increased risk of dementia. Individuals in quintiles 3–5 of optimal macronutrient score had a lower risk of dementia compared with those in quintile 1 (HR (95%CI): 0.76(0.64–0.91) for quintile 3, 0.71(0.60–0.85) for quintile 4, 0.74(0.61–0.91) for quintile 5). The association between macronutrient score and incident dementia was significant across subgroups of age, gender, education, and smoking. Conclusion: Moderate intakes of carbohydrate, fat, and protein were associated with the lowest risk of incident dementia.