By Lisa Mosconi, PhD

Associate Director, Alzheimer’s Prevention Clinic/Department of Neurology, Weill Cornell Medical College

Dr. Mosconi reports no financial relationships relevant to this field of study.

SYNOPSIS: MRI of the brain in community-dwelling people (average age, 60 years) revealed that a long-term, high-quality diet was associated with larger hippocampal volumes after an average interval of 11 years.

SOURCE: Akbaraly T, Sexton C, Zsoldos E, et al. Association of long-term diet quality with hippocampal volume: Longitudinal cohort study. Am J Med 2018; Jul 26. doi: 10.1016/j.amjmed.2018.07.001. [Epub ahead of print].

Results from many recent studies have supported the beneficial effect of diet and nutrition on the development of cognitive decline and Alzheimer’s disease. Researchers have found that diet not only therapeutically affects cognitive function, but also improves mood, cardiovascular risk, weight loss, and insulin resistance. Although researchers have examined how diet affects many cognitive outcomes, such as memory scores and progression to a diagnosis of mild cognitive impairment or Alzheimer’s disease, few have investigated how diet affects brain biomarkers of Alzheimer’s disease, especially among middle-aged, cognitively intact individuals. This information is critical when evaluating diet to prevent brain aging and dementia.

Akbaraly et al examined nutritional quality as a predictor of hippocampal volume, a well-established marker of Alzheimer’s disease risk, in a prospective cohort of community-dwelling participants from the Whitehall II study, which was designed to investigate long-term health outcomes, particularly cardiovascular disease prevalence and mortality rates, among 10,308 British civil servants recruited between 1985 and 1988.1 Participants were 35-55 years of age at the beginning of the study. Two-thirds were men and one-third women.

Akbaraly et al focused on a subset of 459 participants who received serial dietary exams and an MRI of the brain an average of 11 years after the study began. Investigators asked participants to use food frequency questionnaires to track their food patterns over the previous 11 years, and conducted examinations approximately every five years. MRI scans were performed once, from 2015-2016. At the time, participants were an average of 60 years of age and 19% were female.

The food frequency questionnaires measured intake of 11 components (foods and nutrients), including six components for which high intakes are considered ideal (e.g., vegetables, fruit, whole grains, nuts and legumes, long-chain omega-3 fats, and total polyunsaturated fatty acids) and five components for which avoidance or low intake is considered ideal (e.g., sugar, sweetened drinks and fruit juice, red and processed meat, trans-fat, and sodium). Based on the intake of these foods and nutrients, researchers calculated Alternative Healthy Eating Index 2010 (AHEI) scores for each participant at each visit.2 A higher score was associated with a higher-quality nutritional diet. Based on AHEI scores, participants were divided into those who maintained a healthy diet, those who maintained a poor-quality diet, those who improved the quality of their diets, and those whose diets degenerated over time.

After adjusting for age, sex, and total calorie intake, higher AHEI scores were significantly associated with larger hippocampal volumes. Each 8.7-point (one standard deviation) increment in AHEI scores was associated with an increase in hippocampal volume by up to 92.5 cc. This effect was independent of several possible confounding factors, such as occupational grade, physical activity, smoking habits, presence of cardiometabolic disorders, cognitive impairment, and depressive symptoms. Additionally, participants who maintained a healthy diet or improved their diet throughout the course of the study showed larger hippocampal volumes compared to those who ate a poor-quality diet.

COMMENTARY

These findings are consistent with previous work showing that short-term diet quality is associated with preserved brain biomarkers of Alzheimer’s disease in middle-aged and older adults.3,4 To further support these associations, the authors of two randomized, controlled trials found additional data to support the importance of nutrition for preventing Alzheimer’s disease. In the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability study, researchers found that a lifestyle intervention including nutrition, exercise, and cognitive training reduced the risk of cognitive decline.5 In the second trial, researchers found that following a Mediterranean-style diet enriched with extra virgin olive oil or a handful of nuts each day improved memory, attention, and executive function compared to a low-fat diet.6 Although additional randomized, controlled trials are needed, recommending targeted dietary interventions in midlife is evidence-based and safe for reducing the risk of cognitive decline and Alzheimer’s dementia.

REFERENCES

  1. Marmot M, Brunner E. Cohort profile: The Whitehall II study. Int J Epidemiol 2005;34:251-256.
  2. Chiuve SE, Fung TT, Rimm EB, et al. Alternative dietary indices both strongly predict risk of chronic disease. J Nutrition 2012;142:1009-1018.
  3. Berti V, Walters M, Sterling J, et al. Mediterranean diet and 3-year Alzheimer brain biomarker changes in middle-aged adults. Neurology 2018;90:e1789-e1798.
  4. Gu Y, Brickman AM, Stern Y, et al. Mediterranean diet and brain structure in a multiethnic elderly cohort. Neurology 2015;85:1744-1751.
  5. Kivipelto M, Mangialasche F, Ngandu T. Lifestyle interventions to prevent cognitive impairment, dementia and Alzheimer disease. Nat Rev Neurol 2018; Oct 5. doi: 10.1038/s41582-018-0070-3. [Epub ahead of print].
  6. Valls-Pedret C, Sala-Vila A, Serra-Mir M, et al. Mediterranean diet and age-related cognitive decline: A randomized clinical trial. JAMA Intern Med 2015;175:1094-1103.