Mental Stimulation May Offset Impact of Poor Diet on Cognition

Pauline Anderson

July 25, 2016

TORONTO — A "Western"-style diet heavy on red meat, processed foods, sugary drinks, and baked goods is associated with cognitive decline, but mental stimulation may help offset this negative effect, a new study suggests.

Evidence suggests that a traditional Western dietary pattern causes adverse brain changes, for example, inflammation, loss of cellular function, and amyloid plaque formation.

But researchers found that having a higher education and an intellectually stimulating occupation, as well as participating in socially engaging leisure activities, protects older adults from the cognitive decline associated with consuming such a diet.

"This is the first time it has been demonstrated that a lifetime history of mental stimulation and high cognitive reserve can partially offset the neurocognitive disadvantages associated with consuming a poor diet," said study author Matthew Parrott, PhD, postdoctoral fellow, Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada.

Dr Matthew Parrott

Dr Parrott presented his research here at a press briefing at the Alzheimer's Association International Conference (AAIC) 2016.

Bad Diet, Cognitive Decline

The Quebec Longitudinal Study on Nutrition and Successful Aging (NuAge) included 351 community-dwelling older subjects without cognitive impairment, mean age 74 years.

Using statistical techniques, researchers identified a Western dietary pattern from food-frequency questionnaires completed by study participants. They assigned each participant a diet score and categorized the participants into "high" or "low" Western diet adherents.

The investigators also looked at the participants' self-reported education level, their engagement in social activities, and the complexity of the workplace position they held the longest, based on the social interaction and intellectual activity required in this position.

According to Dr Parrott, examples of the most complex occupations include senior management positions, lawyers, teachers, social workers, engineers, physicians, dentists, and pharmacists, whereas the least complex jobs include laborers, such as groundskeepers and construction workers.

Participants with two or more of these factors were considered to have a high cognitive reserve.

Researchers examined the association of the Western dietary pattern with cognitive function as measured by the modified Mini-Mental State Examination (3MSE) score at baseline and over 3 years. They split the diet group into those with high and low cognitive reserve.

They found that those who ate poorly, even if they had mental stimulation, started out at a lower 3MSE score.

"There is a cost to eating poorly, even for those with a mentally stimulating lifestyle or high cognitive reserve" said Dr Parrott.

In the low cognitive reserve group, a "bad" diet was associated with more cognitive decline over 3 years. There was a relatively large difference in decline between the high and low Western diet groups.

"Critically, we didn't see that in people with high cognitive reserve, so there's no association between bad diet and cognitive decline in people with mentally stimulating lifestyle," said Dr Parrot, adding that the trajectories of the two diet groups with high cognitive reserve was more equal.

The only "potential fly in the ointment", he added, is that "if you had a bad diet, even if you had a mentally stimulated lifestyle, you started a bit lower," although after 3 years, "you're still doing better than someone with an equally bad diet but who is in the low cognitive reserve group."

The study "clearly shows" that poor diet and a lifetime history of mentally stimulation "combine to influence vulnerability to dementia", said Dr Parrott.

"Older adults with a mentally stimulating lifestyle and who limited consumption of food associated with a traditional Western diet appear least at risk of dementia."

Although cognitive reserve doesn't provide "complete protection," it looks like it does help slow down cognitive decline, he said.

Social Interaction Underestimated?

Commenting on the study for Medscape Medical News, press briefing moderator, Mary Sano, PhD, professor of psychiatry, director of Alzheimer's Disease Research Center, and associate dean of clinical research, Mount Sinai School of Medicine, New York, New York, and a member of the Medical & Scientific Advisory Council, Alzheimer's Association, noted that while some lifestyle risk factors can have "a really detrimental effect," this study suggests that the detrimental effect "is biggest or largest" in people who have lower education, less stimulating jobs, and fewer opportunities to engage with others.

It looks as though, in some ways, the negative impact of diet "can be overcome," she added.

The "social interaction piece" is "very exciting" but may "be ignored" by some doctors, said Dr Sano.

"We tell our patients to improve their physical activity and we also think that puzzles et cetera are important, but clearly, what we are seeing is this real advantage to having social interaction. So maybe clinicians should be encouraging that type of activity right here and now."

The study received funding from the Canadian Consortium on Neurodegeneration in Aging, Canadian Institutes of Health Research and the Fonds de recherche Santé Quebec. Dr Parrott has disclosed no relevant financial relationships.

Alzheimer's Association International Conference (AAIC) 2016. Abstract P2-421. Presented at press briefing July 24, 2016, and at meeting July 25, 2016.

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