A number of studies have suggested that eating a healthy diet may reduce a person's risk of dementia, but a new study has found that two diets including the Mediterranean diet are not linked to a reduced risk of dementia. The study is published in the October 12, 2022, online issue of Neurology®, the medical journal of the American Academy of Neurology.

The Mediterranean diet includes a high intake of vegetables, legumes, fruits, fish and healthy fats such as olive oil, and a low intake of dairy products, meats and saturated fatty acids.

"Previous studies on the effects of diet on dementia risk have had mixed results," said study author Isabelle Glans, MD, of Lund University in Sweden. "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."

For the study, researchers identified 28,000 people from Sweden. Participants had an average age of 58 and did not have dementia at the start of the study. They were followed over a 20-year period. During the study, participants filled out a seven-day food diary, a detailed food frequency questionnaire and completed an interview. By the end of the study, 1,943 people, or 6.9%, were diagnosed with dementia, including Alzheimer's disease and vascular dementia.

Researchers examined how closely participants' diets aligned with conventional dietary recommendations and the Mediterranean diet.

After adjusting for age, gender, and education, researchers did not find a link between following either a conventional diet or the Mediterranean diet and a reduced risk of dementia.

Glans noted that further research is needed to confirm the findings.

Nils Peters, MD, of the University of Basel in Switzerland, who wrote an editorial accompanying the study, said, "Diet on its own may not have a strong enough effect on memory and thinking, but is likely one factor among others that influence the course of cognitive function. Dietary strategies will still potentially be needed along with other measures to control risk factors."

A limitation of the study was the risk of participants misreporting their own dietary and lifestyle habits.

The study was funded by the Swedish Research Council, the Knut and Alice Wallenberg foundation, the Marianne and Marcus Wallenberg foundation, at Lund University, the Swedish Alzheimer Foundation, the Swedish Brain Foundation, and other organizations.

Who else suffers from dementia?