Contrary to some prior studies, new research suggests that a healthy diet, including the Mediterranean diet, does not reduce dementia risk.

After adjusting for relevant demographic and other lifestyle measures, there was no association between adherence to healthy dietary advice or the Mediterranean diet on the future risk of dementia or beta-amyloid (Aβ) accumulation.

“While our study does not rule out a possible association between diet and dementia, we did not find a link in our study, which had a long follow-up period, included younger participants than some other studies and did not require people to remember what foods they had eaten regularly years before,” study investigator Isabelle Glans, MD, of Lund University in Sweden, said in a news release.

The findings were published online October 12 in Neurology.

No Risk Reduction

Several studies have investigated how dietary habits affect dementia risk, with inconsistent results.

The new findings are based on 28,025 adults (61% women; mean age, 58 years at baseline) who were free of dementia at baseline and were followed over a 20-year period as part of the Swedish Malmö Diet and Cancer Study. Dietary habits were assessed with a 7-day food diary, detailed food frequency questionnaire, and in-person interview.

During follow-up, 1943 individuals (6.9%) developed dementia.

Compared to those who did not develop dementia, those who did develop dementia during follow-up were older and had a lower level of education and more cardiovascular risk factors and comorbidities at baseline.

Individuals who adhered to conventional healthy dietary recommendations did not have a lower risk of developing all-cause dementia (hazard ratio [HR] comparing worst with best adherence, 0.93; 95% CI, 0.81 – 1.08), Alzheimer’s disease (HR, 1.03; 95% CI, 0.85 – 1.23) or vascular dementia (HR, 0.93; 95% CI, 0.69 – 1.26).

Adherence to the modified Mediterranean diet also did not appear to lower the risk of all-cause dementia (HR, 0.93; 95% CI, 0.75 – 1.15), Alzheimer’s disease (HR, 0.90; 95% CI, 0.68 – 1.19), or vascular dementia (HR, 1.00; 95% CI, 0.65 – 1.55).

There was also no significant association between diet and AD-related pathology, as measured by cerebrospinal fluid analysis of Aβ42 in a subgroup of 738 participants. Various sensitivity analyses yielded similar results.

Diet Still Matters

The authors of an accompanying editorial note that diet as a “singular factor may not have a strong enough effect on cognition, but is more likely to be considered as one factor embedded with various others, the sum of which may influence the course of cognitive function (diet, regular exercise, vascular risk factor control, avoiding cigarette smoking, drinking alcohol in moderation, etc).

“Diet should not be forgotten and it still matters” but should be regarded as “one part of a multidomain intervention with respect to cognitive performance,” write Nils Peters, MD, with University of Basel, Switzerland, and Benedetta Nacmias, PhD, with University of Florence, Italy.

“Key questions that remain include how to provide evidence for promoting the implications of dietary habits on cognition? Overall, dietary strategies will most likely be implicated either in order to reduce the increasing number of older subjects with dementia, or to extend healthy life expectancy, or both,” Peters and Nacmias say.

The study had no commercial funding. Glans, Peters, and Nacmias have disclosed no relevant financial relationships.

Neurology. Published online October 12, 2022. Full text, Editorial

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