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 “It is likely that a healthy diet has effects on cardiovascular risk
factors and cardiovascular disease, and that this is an important
mechanism for reducing the risk of cognitive decline,” said lead
author Andrew Smyth of McMaster University in Hamilton, Ontario,
Canada, and the National University of Ireland in Galway.
The results were similar when researchers excluded people who had
overt clinical events like stroke, suggesting that the benefit may
also reduce the risk of cognitive decline for people without such
clear indicators of advanced cardiovascular disease, Smyth told
Reuters Health by email.
“As our study is observational, we can only say that a healthy diet
was associated with a reduced risk of cognitive decline and cannot
definitively say there is a causal relationship,” he said.
Smyth and his coauthors used data from two multinational randomized
trials of a blood pressure medication. They included more than
27,000 men and women age 55 and older who had a history of coronary,
cerebral or peripheral artery disease or high-risk diabetes and who
were followed until death, stroke, heart attack or hospitalization.
Half the participants were followed for less than five years.
Participants filled out a 20-point food frequency questionnaire at
the beginning of the trials and completed a mini-mental state exam
at least twice during their respective trials.
Of the 27,000 total participants, 4,699 or almost 17 percent
experienced marked cognitive decline based on their mental state
exams.
The researchers used the food frequency questionnaire to estimate
how “healthy” people’s dietary habits were, awarding higher scores
to frequent consumption of foods like vegetables, fruits, nuts, soy
proteins and fish.
The top fifth of people with the healthiest diets were about 24
percent less likely to experience cognitive decline during the study
than the bottom fifth with the worst diet scores, the study team
reports in Neurology.
“Our study shows that those with the healthiest diet tended to be
more active, were less likely to smoke and had lower body mass
index,” Smyth said. “This suggests that the consumption of a healthy
diet is likely to be associated with a healthy lifestyle in
general.”
About 14 percent of people in the healthiest diet category had
cognitive decline compared to 18 percent of those in the
least-healthy category after taking physical activity, high blood
pressure and cancer history into account.
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“As foods and nutrients are not consumed in isolation, and the
reduction in intake of one food usually results in increased intake
of other foods, we think that rather than focus on particular foods,
it is more important to focus on overall diet quality,” Smyth said.
“For example, some of the reported benefits of ‘healthy’ food
choices may be lost by ‘unhealthy’ choices.”
The study was not designed to quantify how much or little people
should change their lifestyles to lower cognitive decline, and there
is no easy way to infer such a conclusion, said Cecilia Samieri, a
researcher at INSERM and Universite de Bordeaux in France who was
not part of the new study.
“It is interesting to notice that people in the top 20 percent of
adherence to healthy diets only appear to be protected, while those
with milder adherence are not,” Samieri told Reuters Health by
email.
All study participants were at high risk for cardiovascular disease,
so the results may not be generalizable to the broader population,
she noted.
“Indeed, to be included in the study, participants had to report a
history of cardiovascular disease or of diabetes, and they may have
modified their diets after the diagnosis, along with being more at
risk to experience accelerated cognitive decline during follow-up,”
she said.
SOURCE: http://bit.ly/1F8awwC
Neurology, online May 6, 2015.
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