Several recent studies have begun to define the involvement of certain genes in the development of Alzheimer s disease. But a new study comparing the occurrence of dementia and Alzheimer s disease among different populations suggests there may be other risk factors for Alzheimer s disease that vary across cultures and nations.
According to an analysis by scientists at the National Institute on Aging (NIA), the University of Hawaii, and the Honolulu Department of Veteran s Affairs, Japanese-American men living in Hawaii have a high rate of Alzheimer s disease — 5.4 percent in this study population — when compared with levels found in several studies of men of similar age living in Japan.
In Japan, rates of Alzheimer s disease are relatively low compared with rates found in the U.S., but the Japanese have higher rates of vascular dementia, another form of dementing illness. According to the new study, first and second generation Japanese-American men who have lived all or most of their lives in Hawaii appear to have a higher risk of Alzheimer s disease, a risk similar to that of European-ancestry Americans. They have not, however, experienced any decrease in their risk of vascular dementia.
Observations from the new study will guide a search for environmental, genetic, and cultural factors that may influence the development of both Alzheimer s disease and vascular dementia.
The study appears in the September 25 issue of the Journal of the American Medical Association. Researchers examined data on 3,734 men aged 71-93. About 9.3 percent of the participants overall were categorized as having dementia. Some 4.2 percent of the Japanese-American men had vascular dementia.
The risk for developing vascular dementia seems unchanged in this population. At the same time, something associated with migration or with exposure to Western environmental factors has led to higher rates of Alzheimer s disease, says Lon White, M.D., chief of the NIA s Asia-Pacific Office and the study s director. Further research in this population, and other cross-national research, should help us identify what those factors may be.
National Institute on Aging