Healthy eating in midlife was associated with better cognitive performance and lower risk of subjective cognitive decline (SCD) in three large prospective studies of US health professionals.
The analysis included participants from three long-running cohorts of US health professionals who were followed for years with repeated dietary assessments and cognitive evaluations. Individuals with the highest adherence to healthy eating patterns, particularly the Dietary Approaches to Stop Hypertension (DASH) diet, had significantly lower risk of SCD and performed better on objective cognitive testing.
For example, participants in the 90th percentile of adherence to the DASH diet had a 41% lower risk of reporting SCD during follow up compared with peers in the 10th percentile.
Of note, the DASH diet was consistently associated with a lower risk of SCD even when measured up to 26 years before the SCD assessments and had robust protective associations at various ages, particularly in midlife (45-54 years).
“These findings support the importance of healthy eating as part of midlife brain-health strategies and motivate pragmatic and implementation research to translate these findings into scalable programs,” investigators, led by Hui Chen, PhD, Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, wrote.
The research was published online February 23 in JAMA Neurology.
Healthy Diet, Healthy Brain
Dementia is projected to affect 150 million people worldwide by 2050. While healthy diets are widely believed to benefit brain health, prior evidence has been inconsistent, and few studies have compared multiple dietary patterns within the same population.
The new analysis focused on 159,347 participants in three long-running cohorts. These included the Nurses’ Health Study (NHS), NHSII, and the Health Professionals Follow-Up Study. The average age at baseline was 44.3 years, and 83% of participants were women.
The researchers evaluated six established healthy dietary patterns in relation to both SCD — an early indicator of cognitive problems preceding detectable deficits — as well as objectively measured cognitive function.
Diet was assessed every 4 years using validated food frequency questionnaires, and cumulative average scores were calculated for six dietary patterns: the Alternate Healthy Eating Index 2010 (AHEI-2010), the DASH diet, the Healthful Plant-Based Diet Index (hPDI), the Planetary Health Diet Index (PHDI), and two data-driven patterns reflecting lower hyperinsulinemia (reverse Empirical Dietary Index for Hyperinsulinemia [rEDIH]) and lower inflammatory potential (reverse Empirical Dietary Inflammatory Pattern [rEDIP]).
SCD was measured using self-reported questions about memory and other cognitive changes, while objective cognition in older NHS participants (age 70+ years) was assessed by telephone using validated tests of global cognition, verbal memory, verbal fluency, and working memory.
Across all six healthy dietary patterns, higher adherence was associated with lower risk of global SCD, with the DASH diet showing the strongest magnitude of effect, the researchers found.
For instance, risk ratios for the increasing quintiles of the DASH score were 1.00, 0.91, 0.78, 0.74, and 0.59 in fully adjusted models.
Comparing participants at the 90th vs 10th percentile of adherence, the risk ratio for SCD was 0.59 for DASH; 0.76 for hPDI and rEDIH; 0.80 for PHDI; 0.84 for AHEI-2010; and 0.89 for rEDIP.
A higher DASH diet score in midlife (ages 45-54 years) showed the strongest association with lower risk of SCD, supporting the concept that midlife may represent a critical window for brain health.
Higher scores across most dietary patterns were also associated with better objectively measured global cognition, with the exception of the hPDI and PHDI patterns.
For instance — compared with those at the 10th percentile of the DASH score — on average, participants at the 90th percentile had a 0.05-higher global cognition z score (equivalent to 0.76 years younger in cognitive aging), a 0.04-higher verbal fluency z score (0.87 years younger), and a 0.05-higher working memory z score (1.37 years younger).
Analyses of individual food groups suggested that higher intake of fish and leafy green, yellow, and other vegetables, as well as moderate wine consumption, was associated with better cognitive outcomes, while red and processed meats, fried potatoes, sweetened beverages, and sweets were linked to worse cognition.
“Our findings generally support the role of a healthy diet, manifested by six dietary patterns, in benefiting cognitive health,” the investigators concluded.
“Further studies with larger sample sizes are needed to reveal modifiers of the diet-cognition association, and large-scale long-term clinical trials are needed to fully reveal the cognitive effects of the healthy diet,” they noted.
The study had no commercial funding. The authors had no relevant disclosures.
