A meta-analysis of studies examining the association between diet and the risk of dementia in individuals over 60 years of age found that those adhering to the Mediterranean diet had an 11% lower risk of developing dementia. The reduction in risk was most pronounced for Alzheimer’s disease, with the elderly following the Mediterranean diet experiencing a 27% lower likelihood of developing Alzheimer’s. The findings were published in Aging Clinical and Experimental Research.
Dementia is a broad category of brain disorders characterized by a decline in memory, language, problem-solving, and other cognitive skills that affect a person’s ability to perform everyday activities. Common types of dementia include Alzheimer’s disease, vascular dementia, Lewy body dementia, and frontotemporal dementia. Dementias are predominantly seen in the elderly. However, they are not a normal part of aging.
At the moment, medical science has no cure for dementia. However, there are treatments believed to alleviate some of the symptoms. Researchers are also intensely exploring lifestyle factors, such as diet, that might reduce the risk of developing dementia. One of these lifestyle factors is adherence to the Mediterranean diet. Previous studies indicated that the Mediterranean diet is associated with various beneficial health outcomes including benefits for the cognitive function.
The Mediterranean diet is characterized by a high intake of whole grains, fruits, vegetables, legumes, and olive oil, moderate consumption of cheese and fish, and limited intake of meat (especially red and processed meats), sweets, and alcohol. Numerous studies suggest that this diet has anti-inflammatory properties, which may be the primary biochemical pathway through which its benefits are mediated.
Study author Daniele Nucci and her colleagues wanted to systematize the findings of previous studies about the links between adherence to the Mediterranean diet and risk of dementia among elderly individuals. They were also interested in estimating how strong this association was for different types of dementia.
To achieve this, the study authors searched PubMed/MEDLINE and SCOPUS databases for studies exploring the question: “Is higher adherence to the Mediterranean diet associated with a lower risk of dementia in the elderly?” They specifically looked for studies examining the relationship between the Mediterranean diet and the risk of dementia in this population.
This search yielded 682 scientific papers. After removing duplicates, studies in languages not understood by the researchers, studies not conducted on humans, non-original works, and papers inadequate for other reasons, 20 studies remained. These studies originated from all continents, with 40% (eight studies) from Europe. Among individual countries, the United States contributed seven studies, Greece and Australia three each, and Sweden two. Other studies came from the Netherlands, France, Italy, China (Hong Kong), Brazil, and Morocco—one from each.
Using this data, the study authors conducted a meta-analysis, a statistical technique that combines the results of multiple scientific studies addressing the same question to derive a more precise estimate of the effect. By pooling data from several studies, a meta-analysis can increase the overall sample size and statistical power, helping to resolve uncertainty when individual studies conflict or provide inconclusive findings.
Results showed that older adults adhering to the Mediterranean diet had 11% lower odds of developing dementia compared to their peers not adhering to this diet. These results were based on studies that altogether included over 59,000 participants. When mild cognitive impairment and Alzheimer’s disease were excluded from the analysis, the reduction in odds was 6%. However, when considering only the risk of Alzheimer’s disease, the results showed that those adhering to the Mediterranean diet had 27% lower odds of developing Alzheimer’s.
“There is a protective effect of the Mediterranean diet when all types of dementia are considered together and when only Alzheimer’s disease is considered individually,” the study authors concluded.
“However, even if the risk reduction is minimal, especially when all types of dementia are considered, it is true that it affects a relatively large number of people, especially the elderly. Therefore, even a small percentage reduction would represent a significant number of people who could potentially prevent dementia just by increasing their adherence to the Mediterranean diet.”
The study sheds light on the links between adherence to the Mediterranean diet and dementia risk in the elderly. However, it is important to note that the design of the studies in this meta-analysis generally does not permit cause-and-effect conclusions to be drawn from the data. It is also possible that other types of diets may offer similar or even stronger protective effects against dementia.
The paper, “Association between Mediterranean diet and dementia and Alzheimer disease: a systematic review with meta‑analysis”, was authored by Daniele Nucci, Andrea Sommariva, Luca Mario Degoni, Giulia Gallo, Matteo Mancarella, Federica Natarelli, Antonella Savoia. Alessandro Catalini, Roberta Ferranti, Fabrizio Ernesto Pregliasco, Silvana Castaldi, and Vincenza Gianfredi.