More than 5 million Americans today are living with Alzheimer’s disease, the most common form of dementia. By 2050, that number could soar as high as 16 million.

The full picture of why some people develop the neurological disorder and others don’t is still hazy. But new research presented at the 2017 Alzheimer’s Association International Conference offers some important clarity. A series of studies confirms that early life stress leads to an increased risk of developing dementia later on. One study found that a single adverse childhood experience can age the brain’s cognitive functioning by four years.

Some populations grapple with more of these stressful early life events than others. The research found African Americans have 60 percent more adverse childhood experiences than any other population. This may help explain why African Americans are twice as likely to develop dementia as white Americans, NPR reports.

This news is distressing, but not surprising, says Northeastern medical sociologist Alisa Lincoln. As a professor of Health Sciences and Sociology and director of the Institute of Urban Health Research and Practice, Lincoln has seen mountains of evidence linking socioeconomic status with mental health. Here, we get her take on the implications of these findings and what can be done about them.

Based on your research, were you surprised by these findings?

No, these findings are not at all surprising. There is a rich literature on the negative impact of both acute and chronic stress on a wide range of health outcomes. In our own work, we have examined the impact of experiences of discrimination on mental health outcomes including depression, anxiety, substance use, and post-traumatic stress disorder in racially and ethnically diverse populations. A person’s social positions—their race, class, gender—all impact not only their access to healthcare, but also their exposures to a range of social and environmental stressors or toxins. What we are seeing here is that the chronic daily stressors of racism, both through individual acts and structural racism associated with poverty and unequal access to employment, education, and housing, are disproportionately experienced by African Americans. Over a life-course, this interacts with other social and biological factors to create increased risk for dementia.

What other negative health outcomes are known to be correlated with stress?

Most health outcomes are associated with stress. Keep in mind, stress is part of the normal human experience. A stressor is anything that requires a person to change or adapt, so these can be both good and bad events. But there are certain types of stress—things like exposure to violence, physical or sexual abuse, neglect, housing instability, or food scarcity—that may be experienced at vulnerable periods in the life course and accumulate across the lifespan. These are often referred to as adverse childhood experiences, and they have a particularly powerful impact on health.

This research suggests that genetics alone are not enough to predict a person’s risk of developing dementia, and that environmental factors play a significant role. How can we continue to untangle the two and get a more accurate picture of dementia and other mental health challenges?

There are few illnesses that can be predicted by genetics alone. And I don’t just say this as a medical sociologist. The best geneticists speak of this as well. As with many complex problems, our best strategies will involve innovative partnerships across disciplines and areas of expertise. At the Institute on Urban Health Research and Practice, we do this by bringing together scientists from sociology, public health, anthropology, criminal justice, biostatistics, psychiatric genetics, psychology, and medicine, along with members of communities impacted by various health and social outcomes.

How can these findings inform further research or public health interventions?

For behavioral health conditions, the picture is likely to be highly complex. But there are many things we do know. We know that the more unequal a society, the higher the rates of distress and poor mental health. We know that marginalization and exclusion worsens mental health outcomes, whether that be through exposure to discrimination, experiences of stigma, or lack of opportunity. We know that exposure to violence and trauma contributes to poor overall health and mental health. And now we know these factors impact prevalence of dementia specifically, and that the impact is even greater on African Americans than on other populations. Public health researchers and professionals have created innovative partnerships and strategies to address these socially-patterned determinants of health, and these most recent findings are an important reminder of the need to continue and re-energize these efforts.