A Tale of Two Cities

African-Americans in Indianapolis develop Alzheimer disease and other dementias at twice the rate of residents of Ibadan, Nigeria.

Evelyn Mason looks wistfully at the framed photograph of her father. "It was so sad to see his faculties decline and watch him become so easily confused about everyday situations," she says. She's describing his descent into what today might be diagnosed as Alzheimer disease, an affliction that affects a higher percentage of African-Americans than white Americans.

But this comparison may not tell the whole story. A ten-year study conducted by researchers at the IU School of Medicine and the University of Ibadan in Nigeria concludes that African-Americans run twice the risk of developing Alzheimer and other forms of dementia than African-Nigerians. The landmark study, which compared Indianapolis residents with Ibadan's Yoruba community, appeared in the Feb. 14 issue of the Journal of the American Medical Association.

"These findings will allow us to pursue the elusive risk factors for Alzheimer in two disparate populations," says Hugh C. Hendrie, MB, ChB, principal author of the study, professor of psychiatry and scientist at the IU Center on Aging Research. "We believe it will lead to genetic and environmental interactions, confirming an opinion that we're on the right track."

One speculation is that environmental factors, such as nutrition, account for the difference. For instance, Ibadan residents typically have a simple diet of vegetables, palm oil and on rare occasions, fish. Indianapolis study participants followed the typical American diet.

Not only were the Nigerians less likely to develop dementia, they also had lower blood pressure and cholesterol, and lower rates of hypertension and diabetes.

The study, which was funded by the National Institute of Aging (which also is supporting the next phase of research), included 2,147 Indianapolis residents and 2,459 Nigerians. Although it was not a perfect match, many African-Americans are believed to be descendants of slaves brought to the U.S. from West Africa. All participants, two-thirds of whom were female, were 65 and older and had no signs of Alzheimer or dementia when the study began in 1991.

In the African-American group, 3.24 percent per year developed dementia, including 2.52 percent who developed Alzheimer disease. In the Nigerian group, 1.35 percent per year developed dementia, including 1.15 percent who developed Alzheimer. In both countries, the majority of those who experienced a dementing disorder developed Alzheimer disease, researchers noted.

Dr. Hendrie, who is affiliated with the IU Center for Aging and the Regenstrief Institute for Health Care, conducted the study with Adesola Ogunniyi, MD, a neurologist at the University of Ibadan; Kathleen S. Hall, PhD, an IUSM epidemiologist; and several others from IUSM.

Evelyn Mason, a retired Indianapolis schoolteacher and administrator who participated in the study, does not suffer from dementia but has witnessed it often in friends and family. The octogenarian, who walks several miles daily and eats a low-fat diet, also exercises her mind by reading professional journals and other publications.

"It's never far removed from my thoughts," she says of Alzheimer. "I often think what some of the signs of the disease are and what would happen with me. That's why I fight so hard. This whole thing is not just a personal challenge but also one for people and science.

"I have a part to play in it, and I'm going to play my part to the 'nth' degree," she adds with a smile.

More detailed information on the Indianapolis-Ibadan study can be found at the Journal of the American Medical Association Web site at http://jama.amaassn.org/issues/ v285n6/rfull/joc01134.html.