Adherence to healthy dietary patterns offers no significant effect on the long-term risk of cognitive decline in a population-based cohort of older Singaporeans, researchers have found.
In cross-sectional analysis, high vs low adherence to alternate Mediterranean diet (aMED) was associated with 65-percent decreased odds of mild cognitive impairment (MCI) (odds ratio, 0.35, 95 percent confidence interval, 0.17−0.73; p=0.005 for trend). This protective association was not observed with the Dietary Approaches to Stop Hypertension (DASH) and Healthy Diet Indicator (HDI) dietary patterns. [J Nutr Health Aging 2026;30:100905]
Longitudinal analysis showed no evidence of association between any of the dietary patterns and the odds of MCI.
“Mediterranean diet has been the most investigated dietary pattern with evidence supporting protection against many age-related diseases, including cognitive decline,” said lead researcher Dr Tao Liu from Nanjing Normal University in Nanjing, Jiangsu, China, and colleagues.
Liu and colleagues offered several explanations for why the significant cross-sectional association between aMED and MCI was not observed in their longitudinal analysis.
“First, the longitudinal analysis involved a substantially smaller sample size due to attrition, which may have reduced statistical power to detect associations. Sensitivity analyses also suggested possible selection bias, as participants retained in the longitudinal cohorts were generally younger and healthier compared with those lost to follow-up,” they said.
“Second, dietary habits in Asian populations differ considerably from those in Western populations, including higher consumption of rice- and soy-based foods and lower consumption of dairy products, red meat, nuts, and alcohol. These differences may limit the applicability and discriminatory ability of predefined Western-derived dietary patterns such as aMED in this population,” they added.
As for the lack of association between the DASH diet and MCI, Liu and colleagues pointed to the unavailability of sodium intake data in the study, which precluded its incorporation into the DASH scoring system. “As sodium restriction is a key component of the DASH diet, omission of this component may have reduced the discriminatory ability of the modified DASH score.”
With regard to HDI, there has been only one prospective study that examined its association with cognitive health outcomes since the establishment of WHO’s 2003 dietary recommendations. Over 12 years of follow-up, HDI showed no significant beneficial effect on any of the outcomes, including Alzheimer’s disease, all-type dementia, and all-type cognitive impairment, in a cohort of elderly Swedish men. [J Alzheimers Dis 2015;43:109-119]
The evidence on HDI in the Swedish cohort is in line with the findings in the present Singaporean cohort and warrants additional longitudinal studies for confirmation and to further minimize the possibility of reverse causality, according to Liu and colleagues.
The researchers emphasized that despite the seemingly lack of long-term protective benefit of healthy diets, adhering to these types of diets remains essential for health, especially for cardiovascular and metabolic health.
“Given the cultural and dietary differences between Asian and Western populations, further longitudinal studies with larger sample sizes, repeated dietary assessments, and more ethnically diverse Asian populations are warranted to determine whether existing predefined dietary patterns are suitable for evaluating cognitive health outcomes in Asian settings, or whether locally derived dietary patterns may be more appropriate,” they said.
A total of 620 community-dwelling older adults (mean age 67.7 years, 71.8 percent female) in Singapore participated in the study. All of them were included in the cross-sectional analyses, while 313 were included in the longitudinal analyses.
Participants with high vs low dietary adherence to aMED were more likely to be women, have greater number of years of schooling, be physically active, and were less likely to be smokers, had lower waist-to-height ratio, lower depression and anxiety scores, and higher Singapore-modified Mini-Mental State Examination (SM-MMSE) scores.
Similarly, participants with high adherence to DASH were more likely to be women, physically active, less likely to be smokers, and had lower waist-to-height ratio, depression, and anxiety scores. There were no differences observed in baseline characteristics between participants in each adherence tertile of HDI.