Two studies presented by Kaiser Permanente researchers Rachel Whitmer, PhD, and Paola Gilsanz, ScD, at an Alzheimer’s conference in July found that early life adversity and birthplace contribute to racial disparities in dementia rates, and that these disparities persist even among the oldest of the elderly.
And another study published by the researchers, also in July, found that being born in the U.S. “Stroke Belt” was associated with dementia risk in a group of individuals who eventually lived outside those states, and that African American persons in that group were at even greater risk.
The first two studies were presented in July at the Alzheimer’s Association International Conference (AAIC) in London.
One study, led by Gilsanz, a postdoctoral fellow at the Division of Research, found that African American patients who were born in 1928 in states with the highest infant mortality rates among African American people faced a 86 percent higher risk of dementia than among white people born in states without high infant mortality rates.
“Infant mortality is a very sensitive marker of early life adversity, not just in a child’s physical environment but also in their social environment,” Gilsanz says. The findings highlight the need to explore how early life conditions influence development of dementia later in life.
Senior research scientist Rachel Whitmer, PhD, and biostatistician Charles P. Quesenberry, PhD, of the Division of Research contributed to the study, which involved examination of data from 6,284 members of Kaiser Permanente Northern California.
“It’s interesting that our results held for people who were born in other states and later came to California,” Gilsanz says.
People over age 90
Gilsanz also contributed to a related study led by Whitmer, in which they and their collaborators analyzed data from 2,351 Kaiser Permanente Northern California members aged 90 and older. They found that old Asian Americans have the lowest cumulative incidence (21%), followed by whites (31%), Latinos (35%) and African Americans (39%) – matching the overall patterns of racial/ethnic disparities in dementia seen in younger elderly. “These are the first estimates of dementia incidence in a diverse cohort of individuals age 90 and older,” Whitmer says. “Given the increasing ethnic diversity in the coming decades, it is imperative to identify what factors contribute to the differences in rates, whether genetic, social, or lifestyle, as some of these factors may be modifiable.”
The Washington Post and NPR covered the AAIC findings, linking them to other recent research into racial disparities in dementia rates and conditions that disproportionately affect African Americans, such as stress and living in a disadvantaged neighborhood.
Birth in “Stroke Belt” states
In a separate study published in JAMA Neurology, Whitmer, Gilsanz, Quesenberry, and colleagues examined whether birth in a high stroke mortality state was associated with increased dementia risk in a group of individuals later living in Northern California with equal access to medical care. The nine states considered high stroke mortality rate state were Alabama, Alaska, Arkansas, Louisiana, Mississippi, Oklahoma, Tennessee, South Carolina and West Virginia, many of which are part of what is commonly considered the “Stroke Belt.”
Dementia was diagnosed in 2,254 of the participants (30.4 percent) and was more common among those born in high stroke mortality states (39.0 percent) than those not born in those states (28.8 percent). Furthermore, individuals who were African American and born in high stroke mortality states had 67 percent greater risk for dementia compared with those individuals who were not African American and not born in high stroke mortality states.
“Future research needs to take a closer look at geographic patterns of dementia risk, and understand how they contribute to racial disparities in rates of dementia,” senior author Whitmer told the New York Times. “It’s pretty powerful that we see these differences.”