High- and Low-Fat Dairy Consumption and Long-Term Risk of Dementia: Evidence From a 25-Year Prospective Cohort Study.

BACKGROUND AND OBJECTIVES: The association between dairy intake and dementia risk remains uncertain, especially for dairy products with varying fat contents. The aim of this study was to investigate the association between high-fat and low-fat dairy intake and dementia risk. METHODS: This study used data from a prospective cohort in Sweden, the Malmö Diet and Cancer cohort, which consisted of community-based participants who underwent dietary assessment at baseline (1991-1996). Dietary intake was evaluated using a comprehensive diet history method that combined a 7-day food diary, a food frequency questionnaire, and a dietary interview. Dementia cases were identified through the Swedish National Patient Register until December 31, 2020, and cases diagnosed until 2014 were further validated. The primary outcome of the study was all-cause dementia, and the secondary outcomes were Alzheimer disease (AD) and vascular dementia (VaD). Cox proportional hazard regression models were used to estimate hazard ratio (HR) and 95% CI. RESULTS: This study included 27,670 participants (mean baseline age 58.1 years, SD 7.6; 61% female). During a median of 25 years of follow-up, 3,208 incident dementia cases were recorded. Consumption of ≥50 g/d of high-fat cheese (>20% fat) was associated with a reduced risk of all-cause dementia (HR 0.87; 95% CI, 0.78-0.97) and VaD (HR 0.71, 95% CI 0.52-0.96) compared with lower intake (<15 g/d). An inverse association between high-fat cheese and AD was found among APOE ε4 noncarriers (HR 0.87, 95% CI 0.76-0.99, p-interaction = 0.014). Compared with no consumption, individuals consuming ≥20 g/d of high-fat cream (>30% fat) had a 16% lower risk of all-cause dementia (HR 0.84, 95% CI 0.72-0.98). High-fat cream consumption was inversely associated with the risk of AD and VaD. Consumption of low-fat cheese, low-fat cream, milk (high-fat and low-fat), fermented milk (high-fat and low-fat), and butter showed no association with all-cause dementia. DISCUSSION: Higher intake of high-fat cheese and high-fat cream was associated with a lower risk of all-cause dementia, whereas low-fat cheese, low-fat cream, and other dairy products showed no significant association. APOE ε4 status modified the association between high-fat cheese and AD. Our study's observational design limits causal inference.