Spotlight: Seattle Kame Project

More than 30 individual studies were produced by the 11-year Seattle Kame Project. Researchers held nearly 7,000 sessions with study participants. Every two years, volunteers were interviewed, answered questionnaires and took mental and physical tests for two to three hours. Studies on factors ranging from cultural ties to soy consumption came out of the project. Some highlights of the research:

Prevalence of dementia: About 6.3 percent of the volunteers suffered from dementia when the project began. The rate is 4.5-5 percent in Japan and as high as 10 percent in mostly Caucasian U.S. populations. Over time, women had a slightly higher risk of developing dementia, and the risk was 2.5 times higher for those with a gene producing a certain cholesterol-carrying protein, ApoE-4.

Brain "reserve": Over four years, 59 volunteers developed Alzheimer's disease. The combination of a small head circumference and the ApoE-4 gene increased the risk of Alzheimer's by 14 times. As people age, brain cells die, and those with smaller heads have fewer cells "in reserve." Compared with healthy volunteers, those with Alzheimer's also were older, less educated and smaller.

Sense of smell: Volunteers with an impaired sense of smell or no smell sense had a moderately increased risk of mental decline. People with no smell sense and the ApoE-4 gene had a five-fold increased risk. Parts of the brain typically affected by early Alzheimer's disease also process smells.

Alcohol consumption: Scores on mental-function tests were higher for those who drank one to seven drinks a week than for teetotalers or heavy drinkers.

Soy consumption and bones: Among 274 women, those who consumed the most soy — mainly tofu, miso and aburage — had the strongest bones. Researchers said more study is needed to determine whether soy can reduce fractures.

Depression: Study participants had a very low rate of depression. Those who immigrated from Japan (Issei) had higher rates than others when first tested, but improved before checkups two and four years later.

— Warren King, Seattle Times medical reporter