A new observational study from the US suggests that exercise combined with a Mediterranean-style diet is linked with a lower risk for Alzheimer’s disease and the researchers said the findings were strong enough to justify setting up controlled trials to investigate the link more robustly and see if there are any other factors that might have an affect on Alzheimer’s risk.
The study was conducted by researchers at the Columbia University Medical Center, New York, New York and was published online on 12 August in the Journal of the American Medical Association (JAMA). The lead author is Dr Nikos Scarmeas, associate professor of clinical neurology in the Department of Neurology, in the Sergievsky Center and in the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at the Center.
Although previous studies have looked at links between diet or physical activity and risk of Alzheimer’s disease (AD), this is the first to look at their combined effect.
“Often times people who exercise also follow a healthy diet and vice versa,” said Scarmeas.
“We wanted to tease out which of these two behaviors may be associated with lower risk for AD, or if the combination of the two is associated with decreased risk even further,” he added.
For the study, Scarmeas and colleagues used data on 1,880 elderly residents of average age 77 who were part of a multi-ethnic community living in Northern Manhattan. None of the participants had dementia at the start of the study.
In interviews that took place at the start of the study, the participants answered questions about their diet and level of physical activity.
For physical activity, the participants were asked to say how much vigorous (eg jogging), moderate (eg hiking or cycling), and light (eg golfing or gardening) they had undertaken in the two weeks prior to the interview.
For diet, they were asked about their food and drink consumption over the previous 12 months. The questions covered nine food categories, the sum of which gave a single score for how close the diet was to a Mediterranean-style one.
A Mediterranean-style diet typically comprises a high intake of fish, vegetables, legumes (eg peas, lentils and beans), fruits, cereals and monounsaturated fatty acids, together with a relatively low intake of dairy foods, meats and saturated fats, and a moderate level of alcohol consumption.
After this, the participants underwent standardized neurological and neuropsychological tests about every 18 months from 1992 to 2006. The researchers then looked for patterns between diet, exercise and diagnosed cases of Alzheimer’s.
The results showed that:
- A total of 282 incident cases of Alzheimer’s disease were diagnosed during a mean follow up of 5.4 years.
- Compared with the participants who were least physically active, the most physically active had a 33 per cent reduction in risk of developing Alzheimer’s disease.
- Compared with those who adhered the least, the participants who adhered the most to a Mediterranean-style diet had a 40 per cent reduction in risk.
- Participants reporting the highest level of exercise and whose diet was closest to the Mediterranean-style showed a 60 percent reduction in risk of developing Alzheimer’s disease compared to those who did not exercise and did not follow a Mediterranean-style diet.
The authors concluded that:
“In this study, both higher Mediterranean-type diet adherence and higher physical activity were independently associated with reduced risk for AD.”
Scarmeas said it seemed that the more they did in terms of both diet and exercise, the lower their risk of develop Alzheimer’s.
But he also said that even a low level of physical activity seemed to have a protective effect.
Scarmeas said the study is important because:
“It shows that people may be able to alter their risk of developing Alzheimer’s by modifying their lifestyles through diet and exercise.”
But he went on to caution that this was an observational, epidemiological study, and not a randomized controlled trial. The data came from self reports, the participants were not randomly assigned to different diet and exercise groups, and there was not control group as there would be in a clinical trial.
“We know that some part of Alzheimer’s is related to genetic changes and as time goes on we discover more and more of these changes. But it is also possible that non-genetic changes, including lifestyle and behavior, may also be affecting our brain health and our risk of developing brain diseases, like Alzheimer’s, maybe in combination with our genetic predisposition,” said Scarmeas.
“We need to understand and learn more about the exact biological mechanisms that may connect physical activity and diet with the biological changes of Alzheimer’s disease,” he urged.
However, he also said that there are now lots of studies linking healthy diet and exercise with various health benefits and prevention of disease, and given that this study and several others also suggest these benefits could extent to brain health, it would not be unreasonable to emphasize to patients and healthy people that lifestyle, and not just genes, impact health, including brain health.
Scarmeas is also a co-author of another French study in the same issue of JAMA that found a link between higher adherence to Mediterranean -type diet and slower rates of cognitive decline but not with lower risk of Alzheimer’s. However, Scarmeas suggests the absence of a link with lower Alzheimer’s risk was most likely due to the limitations of the study design, such as the small numbers of participants who developed Alzheimer’s and the fact it examined a Mediterranean population.
“Physical Activity, Diet, and Risk of Alzheimer Disease.”
Nikolaos Scarmeas; Jose A. Luchsinger; Nicole Schupf; Adam M. Brickman; Stephanie Cosentino; Ming X. Tang; Yaakov Stern.
Published online 12 August 2009.
Additional source: Columbia University Medical Center.
Written by: Catharine Paddock, PhD