NEW YORK -- The so-called Mediterranean diet appears to lower mortality among Alzheimer's patients, with a possible dose-response effect, researchers reported.
NEW YORK, Sept. 10 -- The so-called Mediterranean diet appears to lower mortality among Alzheimer's patients, with a possible dose-response effect, researchers reported.
In the study's highest tertile, adherence to the Mediterranean diet produced a 73% mortality risk reduction, leading to an average survival of nearly four years longer than those in the lowest tertile of adherence, Nikolaos Scarmeas, M.D., of Columbia University here, and colleagues reported in the Sept. 11 issue of Neurology.
More research is needed to determine whether eating a Mediterranean diet also slows the rates of cognitive decline, helps patients maintain their daily living skills, and improves their quality of life, Dr. Scarmeas said.
The diet is characterized by a high intake of vegetables, legumes, fruits, and cereals; high intakes of unsaturated fatty acids (mostly olive oil), but a low intake of saturated fatty acids; a moderately high intake of fish, a low-to-moderate intake of dairy products (mostly cheese or yogurt); a low intake of meat and poultry; and a regular but moderate intake of wine, generally during meals.
The researchers noted that they had recently shown that higher adherence to a Mediterranean diet versus a more traditional Western diet was associated with a lower Alzheimer's risk.
Because the diet has been associated with a lower risk for a series of other medical conditions, the researchers hypothesized that it might also reduce mortality in Alzheimer's patients.
The study included 192 community-based patients in who were prospectively followed for a mean of 4.4 years after a diagnosis with Alzheimer's disease.
Adherence to the diet was the main predictor of mortality in Cox models adjusted for period of recruitment, age, gender, ethnicity, education, APOE genotype, caloric intake, smoking, and body mass index.
Eighty-five Alzheimer's patients (44%) died during the course of the four years-plus of follow-up.
In unadjusted models, higher adherence to the Mediterranean diet was associated with a lower mortality risk (for each additional diet point hazard ratio [HR] 0.79; 95% CI 0.69 to 0.91; P=0.001).
This results remained significant after controlling for all covariates, (HR 0.76; 0.65 to 0.89; P=0.001).
In adjusted models, compared with Alzheimer's patients in the lowest adherence tertile, those in the middle tertile lived 1.33 years longer with a lower mortality risk (0.65; 0.38 to 1.09; 1.33 years longer survival).
Patients in the highest tertile lived an average of 3.9 years longer with an even lower mortality risk (0.27; 0.10 to 0.69; 3.91 years' longer survival; P for trend = 0.003).
Adjustments for all potential confounders made the associations even stronger with a 29% to 35% lower mortality risk for the middle and a 67% to 73% lower mortality risk for the highest tertile, the researchers said.
The majority of the patients were nonwhite. However, excluding the white patients and repeating the analyses for black and Hispanic patients did not change the associations, the researchers reported.
Because higher adherence to the diet is associated with lower mortality in Alzheimer's disease, the gradual reduction in mortality risk for higher diet adherence suggests a possible dose-response effect, Dr. Scarmeas and his colleagues said.
The researchers also reviewed a list of potential study limitations. These included the fact that food frequency inventories may have underestimated the overall quantity of food in each category, possible disease misclassification, and the possibility that diet was related to socioeconomic status or to other characteristics related to better health and a lower risk of Alzheimer's.
Another explanation might be that different adherence to the diet could be an indirect index of Alzheimer's severity, as well as potential inaccuracies in dietary reports by subjects with cognitive problems.
On the other hand, they said, dietary data were collected with a previously validated and widely used instrument.
Measures for multiple potential mortality risk factors were carefully recorded and adjusted for in the analyses, and the Alzheimer's diagnosis took place in a university hospital with expertise in dementia.
In an accompanying editorial, James E. Galvin, M.D., of Washington University in St Louis emphasized the importance of dietary changes, as well as exercise and mental stimulation in modifying the course of cognitive decline and delaying mortality.
It is interesting, he wrote, that considering all the medical and pharmaceutical advances made in the last century, perhaps the most important things we can still tell our patients, is to stay mentally active and physically fit and to eat a healthy and balanced diet.
The study was supported by federal NIA grants, the Charles S. Robertson Memorial Gift for Research in AD, the Blanchette Hooker Rockefeller Foundation, the New York City Council Speaker's Fund for Public Health Research, and
the Taub Institute for Research on AD and the Aging Brain.
Dr. Galvin, the editorial writer, reported no conflicts of interest.