Mediterranean Diet and Physical Activity May Lower Risk of Alzheimer's Disease
Both strong adherence to a Mediterranean-type diet and a high level of physical activity were independently associated with a reduced risk for Alzheimer’s disease, researchers reported in the August 12 JAMA. A second study in the same issue, however, found that although higher adherence to a Mediterranean diet did lead to slower cognitive decline per score on the Mini-Mental State Examination (MMSE), it was not associated with a risk for incident dementia.
Combined Effect of Physical Activity and Diet
Nikolaos Scarmeas, MD, and colleagues conducted the first study to examine the combined association of diet and physical activity with risk for Alzheimer’s disease. Prior research had found an association between a lower rate of Alzheimer’s disease and either physical activity or the Mediterranean diet—which is characterized by high consumption of fruits, vegetables, legumes, cereals, and fish.
Dr. Scarmeas’s group analyzed data regarding diet and physical activity of 1,880 community-dwelling elders without dementia (mean age, 77) who were living in New York City. Subjects underwent neurologic and neuropsychologic evaluations every 1.5 years between 1992 and 2006. Mediterranean-type diet adherence was trichotomized into low, middle, or high scores and dichotomized into low or high scores. Weekly participation in various physical activities was weighted by the type of activity—light (eg, walking, gardening), moderate (eg, bicycling, hiking), or vigorous (eg, jogging, aerobic dancing)—and was trichotomized into no, some, or much physical activity and dichotomized into low or high activity.
Diet adherence and physical activity—separate and combined—were the main predictors in Cox proportional hazards models, which were adjusted for cohort, age, sex, ethnicity, education, apolipoprotein E genotype, caloric intake, BMI, and other variables. The main outcome measure was time to incident Alzheimer’s disease.
Dr. Scarmeas and colleagues identified 282 incident cases of Alzheimer’s disease during a mean follow-up of 5.4 years. When compared with low Mediterranean diet adherence score, the hazard ratio (HR) for middle diet score was 0.98, and the HR for high diet score was 0.6. Compared with no physical activity, the HR for some physical activity was 0.75, and the HR for much physical activity was 0.67. Both physical activity and diet adherence were significantly associated with a lower risk of Alzheimer’s disease incidence when considered simultaneously.
“The highest tertiles for both physical activity and Mediterranean-type diet were associated with a 61% to 67% lower risk of Alzheimer’s disease, an association present after adjusting for multiple potential confounders,” stated Dr. Scarmeas, Associate Professor of Clinical Neurology at the Sergievsky Center and the Taub Institute for Research on Alzheimer’s Disease and the Aging Brain at Columbia University Medical Center in New York City. “Therefore, it seems that both eating well and participating in physical activity may independently confer Alzheimer’s disease–related health benefits.
“In these models, belonging to the middle diet adherence tertile was associated with a 2% to 14% risk reduction, while belonging to the highest diet adherence tertile was associated with a 32% to 40% reduced risk,” Dr. Scarmeas and coauthors observed. “Similarly, compared with individuals with no physical activity, individuals reporting some physical activity had a 25% to 38% lower risk for Alzheimer’s disease, while individuals reporting much physical activity had a 33% to 48% lower risk for Alzheimer’s disease.”
According to the investigators, “This study suggests that more physical activity is associated with a reduction in risk for developing Alzheimer’s disease. The gradual reduction in risks for higher tertiles of physical activity also suggests a possible dose-response association…. Because participating in physical activity and healthy eating are often related to each other (as shown in the present study), it could be argued that the association between physical activity and Alzheimer’s disease is just a manifestation of more physically active individuals eating healthier. Nevertheless, their association with lower rates of Alzheimer’s disease development was independent of each other.”
Mediterranean Diet, Cognitive Decline, and Dementia
Catherine Féart, PhD, and colleagues investigated a potential association of a Mediterranean diet with change in cognitive performance and risk for dementia in 1,410 adults, age 65 and older, from Bordeaux, France. Participants were reexamined at least once over five years, and adherence to a Mediterranean diet (score 0 to 9) was computed from a food frequency questionnaire and 24-hour recall.
Main outcome measures were cognitive performance as measured by the MMSE, Isaacs Set Test, Benton Visual Retention Test, and Free and Cued Selective Reminding Test (FCSRT).
The researchers found that higher diet score was associated with fewer MMSE errors after adjusting for age, sex, education, marital status, energy intake, physical activity, depressive symptoms, and apolipoprotein E genotype, in addition to other factors. “In this population-based cohort study, higher adherence to a Mediterranean-type diet was associated with slower decline on the MMSE but not other cognitive tests and was not associated with the risk for incident dementia over five years of follow-up,” reported Dr. Féart, of the Université Victor Segalen in Bordeaux, and colleagues. However, a higher adherence to the Mediterranean diet was significantly associated with better cognitive performances on episodic memory (FCSRT performances) over time, especially in subjects who remained free from dementia for five years.
