Diet for Prevention of Cognitive Decline in Older Adults

Ms. Apple is a 74-year-old woman with a history of overweight but otherwise very active and still working as a part-time schoolteacher. At a primary care visit, she explains that she is concerned about memory loss because her mother developed dementia in her 70s. She says a friend recommended that she add more extra virgin olive oil to her diet to avoid memory loss and asks your opinion about whether a change in her diet might prevent her own dementia diagnosis.

With an almost three-fold increase in the number of individuals with dementia projected globally between 2019 and 2050 (from 57.4 million cases to 152.8 million cases), the demand for therapeutic solutions is high. Although evidence for pharmacologic interventions aimed at slowing the reduction of amyloid plaques has gained national attention recently, a lifestyle change could avoid the adverse effects associated with medication and likely have other health benefits. However, as we all know, lifestyle changes can be more difficult to implement than taking a daily pill or receiving an infusion.

Certain foods (e.g., flavonoids and antioxidants) have been linked with improved memory and cognition in cohort and observational studies. However, randomized controlled trials of dietary interventions are difficult to conduct because of the challenges of adhering to a lifestyle change. In the Trial of the MIND Diet for Prevention of Cognitive Decline in Older Persons, published in NEJM in July 2023, researchers evaluated the effects of a diet designed to improve brain health on cognitive performance.

Individuals aged ≥65 years with a family history of dementia, scores of at least 22 out of 30 on the Montreal Cognitive Assessment, suboptimal diets, and overweight were randomly assigned to follow the MIND diet (a hybrid of the Dietary Approaches to Stop Hypertension [DASH] and the Mediterranean diet with mild caloric restriction) or a control diet that consisted of mild caloric restriction. Although global cognition scores increased from baseline in both groups and weight loss was similar, the scores ultimately did not differ significantly between groups after 3 years.

While incorporating more extra virgin olive oil, fruits, and whole nuts into her diet likely will not harm Ms. Apple, unfortunately it may not necessarily prevent memory loss when compared to calorie restriction alone.

Read the following NEJM Journal Watch summary for more details of this study.

Rahul B. Ganatra, MD, MPH, reviewing Barnes LL et al. N Engl J Med 2023 Jul 18

Epidemiologic studies suggest an association between diet and dementia risk in older adults, but whether diet can improve cognitive function is unknown. In this study, 600 overweight older adults (mean age, 70; mean body-mass index, 34 kg/m2) with family histories of dementia were randomized to consume the MIND diet (a combination of the Mediterranean diet and the Dietary Approaches to Stop Hypertension [DASH] diet) or to practice portion control alone. Participants in each group received weekly individualized telephone counseling from a dietician for the first 6 months, and then every other week for 3 years, with the goal of achieving loss of 3% to 5% of baseline weight. Participants in the MIND group were provided with presumed “brain-healthy” foods (including olive oil, blueberries, and mixed nuts) every week; the control group received weekly gift cards.

At 3 years, overall and domain-specific cognitive scores increased in both groups compared with their respective baselines, but no difference was noted in scores between the MIND diet and the control group. Mean weight loss was 5 kg in both groups, and magnetic resonance imaging of the brain, obtained in a subset of patients, revealed no differences between groups.

Comment: This study was done well: Little loss to follow-up occurred, and adherence to the MIND diet was confirmed with questionnaires and measurements of serum biomarkers. The fact that both groups saw improvements suggests that dietary changes in both the MIND and control groups — or the associated weight loss — had beneficial effects on cognition. Alternatively, study participants in both groups might have engaged in other behaviors associated with improved cognition, unrelated to dietary constituents or weight loss.

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Abigail Schubach, MD, is a 2023–2024 NEJM Editorial Fellow. She is currently an internal medicine hospitalist at Brigham and Women’s hospital. She completed her internal medicine residency at University of Rochester.