Association between dietary fat intake and long-term risk of dementia: a prospective cohort study

Evidence on the association between dietary fat intake and dementia is inconsistent.

The aim of this study was to examine the prospective associations of total dietary fat and specific fatty acids with incident dementia among middle-aged and older adults.

In the Health and Retirement Study, 5944 participants (59.6% women; mean age 68.0 y) free from dementia at baseline were followed up for a median of 6.0 y. Dietary fat intake (total, animal, and vegetable) and specific fatty acids (saturated, monounsaturated, polyunsaturated, and trans) were assessed using a 164-item food frequency questionnaire. Incident dementia was ascertained using the Langa-Weir classification strategy. Cox proportional hazards models were used to estimate the corresponding hazard ratios (HRs) and 95% confidence intervals (CIs).

During a total follow-up of 31,088 person-years, 444 dementia cases were identified. Higher intake of vegetable fat was associated with a lower risk of dementia (multivariable-adjusted HR_{highest quintile (Q5) vs lowest quintile (Q1)}: 0.69; 95% CI: 0.49, 0.97; P-trend = 0.023). Replacing 5% of total energy intake from animal fat with vegetable fat corresponded to a lower risk of dementia (HR: 0.85; 95% CI: 0.74, 0.96; P = 0.012). The highest intake of monounsaturated fatty acids also showed an inverse relationship with dementia risk (HR_Q5vsQ1: 0.63; 95% CI: 0.42, 0.94; P-trend = 0.016). Conversely, a higher intake of saturated fatty acids was associated with a higher risk of dementia (HR_Q5vsQ1: 1.56; 95% CI: 1.05, 2.32; P-trend = 0.012). Isocaloric substitution of saturated fatty acids with monounsaturated fatty acids (HR: 0.52; 95% CI: 0.33, 0.82; P = 0.005) and polyunsaturated fatty acids (HR: 0.67; 95% CI: 0.48, 0.93; P = 0.016) was significantly associated with a lower dementia risk.

The study demonstrated the heterogeneous associations between different types of dietary fats and risk of dementia. Replacing animal fat and saturated fat with vegetable fat and monounsaturated fats could serve as a dementia prevention strategy.