Mediterranean diet and Alzheimer disease mortality -- Synopsis

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Consuming what's known as a Mediterranean diet -- one loaded with fruits, vegetables, grains and olive oil -- may help Alzheimer's patients live longer, a new study suggests.

The observation comes after researchers tracked the dietary habits of people diagnosed with early-stage Alzheimer's. It follows on earlier work by the same team that suggests these diets may lower the risk of developing Alzheimer's in the first place.

"This time, we found that Alzheimer's patients who were following the Mediterranean diet had longer survival as compared to those who were following the diet less," said study lead author Dr. Nikolaos Scarmeas, an assistant professor in the department of neurology at Columbia University Medical Center in New York City.

The study is published in the September issue of Neurology.

According to the American Heart Association, diets native to the 16 countries bordering the Mediterranean Sea vary somewhat region to region. However, most regimens include a high intake of fruits, vegetables, breads, cereals, potatoes, beans, nuts, seeds, and olive oil. More than half of all fat-sourced calories in the Mediterranean diet come from monounsaturated fats, such as olive oil. Dairy, fish, poultry, and other sources of saturated fats are eaten at low to moderate levels, the AHA say.

Heart disease rates in Mediterranean nations are lower than in the United States, the AHA adds, although it's not clear that diet alone is responsible for the difference.

To further examine the potential health benefits of the Mediterranean diet, Scarmeas' team compared nutrition and disease progression between 1992 and 2002 among 192 patients with early-stage Alzheimer's, all of whom lived in New York City.

All the patients were 65 and older, most were non-white, and all underwent initial physical and neuro-psychological exams to assess their cognitive capacities. Such evaluations were repeated every 18 months.

In addition, the patients completed questionnaires regarding their food consumption over a one-year period. Daily caloric intake was tallied for seven categories, including dairy, meat, fruits, vegetables, legumes, cereals, and fish.

At no time were patients given any information about nutrition, or instructions about what to eat or how much to eat of any particular food group.

Throughout the full study period, the researchers tracked patients for an average of four-and-a-half years, during which time 85 patients died.

Scarmeas' group found that patients whose consumption habits most closely tracked that of the Mediterranean diet were 76 percent less likely to die in the study period than those whose food intake least mimicked the diet.

Compared with those whose diets most closely resembled a Western diet, Alzheimer's patients who most closely followed the Mediterranean diet lived an average of four years longer.

A more moderate degree of adherence to the Mediterranean diet still translated into an extra 1.3 years of survival, the researchers said. That's equal to a 29 percent to 35 percent reduced risk for dying during the study period.

The findings appeared to hold up regardless of patient body mass index, gender, ethnicity, or educational background. Age differences had a nearly imperceptible impact on the findings.

The researchers did not examine how differences in end-of-life care protocols -- such as the possible use of artificial feeding mechanisms and antibiotic therapies -- might have affected survival in some patients.

Scarmeas emphasized that more work needs to be done to tease out the diet's effects.

"For now, we can only speak about the tendency we found in a whole population," he cautioned. "It is possible that particular people happen to have a constellation of several other factors that contribute to a risk for dying or delay their mortality. So, right now, we can only say that in this observational study we found, in general, that the more you follow this Mediterranean diet, the later you die, even after the onset of Alzheimer's disease."

Greg M. Cole is associate director of the Alzheimer's Disease Research Center at the UCLA David Geffen School of Medicine and a neuroscientist with the Greater Los Angeles VA Healthcare System. He described the findings as provocative but not definitive.

"It could be that the Mediterranean diet is slowing the progression of Alzheimer's," he acknowledged. "But there could also be other explanations. For example, a lot of people who have Alzheimer's also have cardiovascular disease. The risk factors for both illnesses show a lot of overlap. And it is a pretty well established benefit that the Mediterranean diet protects against heart disease."

"So, it could be that the Mediterranean diet is actually slowing down the accompanying spectrum of vascular problems that lead to stroke and heart attack and other problems associated with a cardiovascular disease that lead to mortality," explained Cole. "So, death is not as good a measure here as the progression of cognitive decline. Is the diet actually slowing down the cognitive decline of Alzheimer's itself? That's the next question. And, if so, that would certainly be a very significant result."

More information

For additional information on the Mediterranean Diet, visit the American Heart Association.

Sources:

Nikolaos Scarmeas, M.D., assistant professor, department of neurology, Columbia University Medical Center, New York City; Greg M. Cole, Ph.D., neuroscientist, Greater Los Angeles VA Healthcare System, and associate director, Alzheimer's Disease Research Center, UCLA David Geffen School of Medicine; Sept. 11, 2007, Neurology

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By Alan Mozes, Healthday News
Week of Sept. 30 - Oct. 6, 2007