Study Finds Low Alzheimer's
Risk in Rural India

NEW YORK (Reuters Health) - The elderly in rural India face a much lower risk of developing Alzheimer's disease than older Americans do, new study findings suggest.

The reason is unclear, but researchers speculate that genetic and environmental factors may help explain the disparity.

The study of nearly 2,700 older Indians from villages in one northern state showed that their rate of Alzheimer's was far lower than that among older adults in one region of Pennsylvania. Over 2 years, there were fewer than 5 Alzheimer's cases per 1,000 Indians each year--in contrast to more than 17 cases per 1,000 Americans.

Dr. Mary Ganguli and colleagues at the University of Pittsburgh report the findings in the September issue of Neurology.

In earlier work, the Pennsylvania researchers had found that these same Indian villages have the lowest reported prevalence of Alzheimer's in the world. About 1% of adults aged 65 and older were found to have the disease.

In this study, the investigators tracked how many new cases arose over 2 years among residents aged 55 and older. Participants took mental exams and their daily functioning was gauged through interviews with family members. Those who showed signs of dementia were examined further to diagnose possible or probable Alzheimer's disease. In the end, there were 10 such cases.

The findings parallel a study released earlier this year in which older Nigerians were found to have about half the Alzheimer's risk of African Americans living in Indianapolis, Indiana. In that study, the researchers speculated that the Nigerians' better vascular health--indicated by their lower blood pressure, cholesterol levels and body weight--could help explain their lower Alzheimer's rate. Some studies have suggested that these and other factors that affect heart health can also influence the brain's susceptibility to disease.

Similarly, the Pittsburgh team speculates that this Indian population either lacks certain risk factors for Alzheimer's or may have unknown protective factors related to diet or other environmental exposures.

Moreover, the report indicates that the population had a low frequency of a gene variant called apoE4--a known risk factor for Alzheimer's.

Still, Ganguli and colleagues note, ``we urge caution in the interpretation and generalization of our results.''

For one, they explain, problems in daily activities that would suggest the beginnings of dementia might have been missed by family members.

``The daily functional demands on older adults in rural India are limited by their living with, and being cared for, by their family members,'' the authors write. ``Further, they live in a 'low-tech' environment that does not include, for example, the daily use of telephones, bank accounts, or supermarkets.''

However, the possibility that this population has ``unique protective factors'' against Alzheimer's should be tested in future studies, the researchers conclude.

SOURCE: Neurology 2001;57:985-989.

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