After an interview with Dan Gasby and B. Smith about her diagnosis of early-onset Alzheimer's disease at age 62, we take a look at the devastating impact that the disease has had on women and minorities.
When former model, restaurateur, author, and TV host B. Smith was diagnosed with Alzheimer's disease at age 62, she had two additional strikes against her: she was African-American and female. African-Americans are twice as likely to get the disease as whites (and Hispanics are 1.5 times as likely), and nearly two-thirds of patients are women, according to the Alzheimer's Association.
Not long after Smith's diagnosis, she and her husband, Dan Gasby, who became her main caregiver, had to close most of their businesses. This, too, is in line with the statistics. African-Americans who leave the workforce to care for a loved one with Alzheimer's disease lose, on average, more than $300,000 in earnings and benefits, according to the African American Network Against Alzheimer's, an advocacy group in Chevy Chase, MD.
Women may be disproportionately affected by the disease because they tend to live longer than men, and aging is the number one risk factor for the disease. Whether additional hormonal factors are implicated is unclear, but "it would make sense that there are underlying differences for women and men," says Heather Snyder, PhD, senior director of medical and scientific operations at the Alzheimer's Association. "We do know that the underlying biology—our immune system and brain metabolism—are different in women and men."
The disease may also have historical antecedents. Men and women have been educated differently over the past 50 years. "We're talking about a group of people 65 and older, so perhaps the women who grew up in that time had less education than men," says Mary E. Quiceno, MD, FAAN, associate professor of neurology and neurotherapeutics at the University of Texas Southwestern Medical Center in Dallas. "With less education, especially less than high school, there is an increased risk of Alzheimer's disease. So with a woman who is 80, maybe the resources were different and she didn't get as much education."
It's also possible that men with cardiovascular disease, another risk factor, die before they have the chance to develop Alzheimer's. "Men aren't living as long so we're not counting them," Dr. Quiceno says. "Maybe that's another difference."
Differences in biology and less access to education may also explain the higher rates of Alzheimer's among minorities. Diabetes, high blood pressure, and heart disease, all of which are higher in the African-American and Hispanic communities, could be contributing risk factors. But experts can't be certain, mostly because those communities haven't been studied very well. Gasby calls the lack of understanding a "21st-century civil rights issue." In general, about 20 percent of people with Alzheimer's disease don't get a diagnosis. That number is even higher in the black community.
Several studies reported in July of this year at the Alzheimer's Association International Conference in London support Gasby's observations. In one, Megan Zuelsdorff, PhD, a postdoctoral trainee at the University of Wisconsin School of Medicine and Public Health in Madison, and colleagues examined the impact of lifetime stressful experiences on cognition as part of the Wisconsin Registry for Alzheimer's Prevention (WRAP) study. They found that a single major stressful event early in life—like being fired from a job, the death of a child, or growing up with a parent who abused alcohol or drugs—is equal to four years of cognitive aging. On average, the study found, African-Americans experience 60 percent more of these types of stressful events than non-Hispanic whites over their lifetimes. "Adversity is a clear contributor to racial disparities in cognitive aging, and further study is imperative," says Dr. Zuelsdorff.
Another study showed that disadvantaged neighborhoods also pose a threat. People in these neighborhoods usually don't have access to healthy food or safe places to exercise. The neighborhoods may also be more polluted or closer to toxic industrial areas. Amy Kind, MD, PhD, associate professor at the University of Wisconsin School of Medicine and Public Health and the lead author of the study, found that people in the most disadvantaged neighborhoods had markedly worse cognitive performance in all aspects measured—working memory, immediate memory, speed and flexibility of cognition, and verbal learning—even after adjusting for age and education. They also had disproportionately higher levels of phosphorylated tau, an Alzheimer's disease biomarker, in their spinal fluid.
"This study provides evidence to suggest that living in a neighborhood challenged by poverty, low education, unemployment, and/or substandard housing may increase the risk of Alzheimer's disease, and may account for some of the observed differences in Alzheimer's disease risk among people of different racial backgrounds and income levels," says Dr. Kind.
In a third study, researchers at the University of California, San Francisco, and Kaiser Permanente found that African-Americans who live in areas of high infant mortality have a 40 percent higher risk of developing Alzheimer's disease than those who live in states with lower infant mortality rates, and an 80 percent higher risk than whites who live in states with low infant mortality rates.
Historically, researchers have not included African-Americans in clinical trials, says John C. Morris, MD, FAAN, an endowed professor of neurology and director of the Knight Alzheimer's Disease Research Center at Washington University in St. Louis. "Research often capitalizes on people who are willing participants. And that's usually upper-middle-class Caucasians," he says. "We haven't done the real work to make sure we have a diverse mix of participants. Also, the people who do Alzheimer's research are largely white males. Hispanics and African-Americans may prefer to see people who look like them when asked to do research."
African-Americans also have historical memories of being discriminated against in the name of science and may not trust researchers, says Dr. Morris. One of the most egregious examples is the 40-year Tuskegee Syphilis Experiment. The study, conducted by the US Public Health Service and the Tuskegee Institute between 1932 and 1972, enrolled 600 poor black men, more than half of whom had syphilis, to watch how the disease progressed untreated. "We investigators have to make the case for why we want African-Americans to volunteer in research," says Dr. Morris.