Dementia Risk and Diet Investigated

The MIND diet was linked with reduced dementia risk, an analysis of observational studies concluded, though the researchers called for more investigations in different populations.

Across three prospective cohort studies and a meta-analysis, adherence to the MIND diet was associated with a lower risk of incident dementia in middle-aged and older adults, reported Changzheng Yuan, ScD, of Zhejiang University School of Medicine in China, and co-authors.

In the meta-analysis, the highest adherence to the MIND diet was tied to a 17% lower risk of dementia compared with the lowest adherence (pooled HR 0.83, 95% CI 0.76-0.90), the researchers reported in JAMA Psychiatry.

The MIND diet -- a hybrid of the Mediterranean and DASH diets -- emphasizes plant-based foods, limits intake of animal-based foods and those high in saturated fat, and promotes eating berries and leafy green vegetables.

The diet has been linked with slower cognitive decline, but few large studies have investigated its relationship with dementia or Alzheimer's disease. One analysis showed a significant relationship with lower dementia risk only in the first 7 years of follow-up, not afterward.

Yuan and co-authors analyzed data about middle-aged and older adults in three large prospective studies: the U.K.'s Whitehall II cohort and, in the U.S., the Health and Retirement Study and the Framingham Heart Study Offspring cohorts. They also conducted a meta-analysis of 11 observational studies.

Participants were dementia-free at baseline. Food frequency questionnaires at or before baseline were used to assess MIND diet scores, with higher scores on the 15-point scale indicating better adherence to the diet.

Whitehall II had about 8,400 participants (69% male) with a mean baseline age of 62. The Health and Retirement Study had about 6,800 participants (59% female) with a mean baseline age of 67; while the Framingham Offspring study had a sample size of about 3,000 (55% female) with a mean baseline age of 64.

Mean baseline MIND diet score was 8.3 in Whitehall II, 7.1 in the Health and Retirement Study, and 8.1 in the Framingham Offspring study. Median follow-up durations were 12.9 years, 5.0 years, and 10.7 years, respectively.

Over 166,516 person-years, a total of 775 people in the three cohorts developed incident dementia. A higher MIND diet score was associated with lower risk of dementia, with a pooled HR of 0.83 (95% CI 0.72-0.95, P for trend=0.01) for every 3-point increment.

Associations were significant in the two U.S. cohorts but not in Whitehall II. Potential contributors included a higher consumption of green leafy and other vegetables, berries, nuts, olive oil, and beans, and lower consumption of red meat and meat products.

The meta-analysis of 11 studies included 224,049 participants with 5,279 incident dementia cases. The association between the MIND diet and dementia risk showed moderate heterogeneity across studies (I²=35%). No single study substantially affected the pooled results.

The researchers couldn't determine whether their results were linked with any specific dementia subtype. The analyses relied on self-reported food intake and, despite relatively long follow-up periods, the findings may be subject to reverse causality.

More work is needed clarify whether a causal relationship exists between the MIND diet and dementia, Yuan and colleagues said.

"Meanwhile, to which extent a healthy diet intervention could reduce dementia risk in specific populations and the optimal intervention time window for this intervention remain largely unknown," they noted. The randomized MIND diet clinical trial may provide more answers soon.

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