THE QUESTION Might the quality of people’s diets affect their retention of memory and thinking skills as they age?

THIS STUDY analyzed data on 27,860 people, 55 and older (average age, 66), most with a history of diabetes or heart disease. Standardized tests of cognitive abilities, given periodically over about a five-year span, identified 4,699 people (about 17 percent of the group) who experienced cognitive decline.

Those who reported eating the most-healthful diets — lots of fruits and vegetables, nuts and fish, very little red meat and moderate amounts of alcohol — were 24 percent less likely to have lost cognitive skills than were those whose diets were the least healthful. Taking into account other factors that might have affected the results, such as physical activity, blood pressure, smoking and cancer, did not alter the findings

WHO MAY BE AFFECTED? Older people. Many people have some decline in memory and thinking skills as they age; others experience more-serious deficits, sometimes affecting their ability to function day to day. Commonly suggested ways to maintain a healthy brain include exercising, staying social, managing stress, getting sufficient sleep and not smoking, as well as watching what you eat.

CAVEATS Dietary data came from the participants’ responses on questionnaires. Factors not accounted for may have affected the results; the researchers noted that unhealthful eating habits “may be a proxy for other poor health behaviors that were either unknown or unmeasured.” Whether the findings would apply to people who have not had diabetes or heart disease remains unclear.

FIND THIS STUDY May 6 online issue of Neurology (www.neurology.org; click on “Ahead of Print”).

LEARN MORE ABOUT cognitive decline at www.helpguide.org (search for “age-related memory loss”). Learn about healthful eating at www.nihseniorhealth.gov (search for “eating well”).

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.