In 2020, the overall life expectancy in the U.S. dropped by 1.5 years, largely due to the COVID-19 pandemic. But the reduction wasn't shared equally among the general population; Native American people lost an average of 4.5 years of life expectancy; Black and Hispanic people lost, on average, 3 years, while white people lost only 1.2 years.

This figure tracks with other health trends: In general, Black and Hispanic people and those living in poverty in the U.S. have worse health outcomes — more high blood pressure, higher rates of diabetes and increased maternal and infant mortality — than the overall population.

Public health researcher Arline Geronimus from the University of Michigan says the traditional belief that the disparities are due to genetics, diet and exercise don't explain data that's accumulated over the years. Instead, she makes the case that marginalized people suffer nearly constant stress from living with poverty and discrimination, which damages their bodies at the cellular level and leads to increasingly serious health problems over time.

Geronimus coined a term for this chronic stress — she calls it "weathering," which, she says, "literally wears down your heart, your arteries, your neuroendocrine systems, ... all your body systems so that in effect, you become chronologically old at a young age." She writes about the phenomenon in her new book, Weathering: The Extraordinary Stress of Ordinary Life in an Unjust Society.

Geronimus' theories drew criticism when she first promoted them in the 1990s. But in recent years, her work has generated a wealth of support. She says weathering helps explain why Black women who give birth in their 20s have more complications than those who become mothers in their teens. The older women had endured the stress of their difficult living conditions longer, she says, and thus had suffered more damage to their health.

"It's not that every Black person has more damage than every white person," she says. "It's really about how much stress versus social support you get in your everyday life. ... Because African Americans and low-income Americans are more likely to suffer more of these stressors, they are more likely to be weathered, weathered severely and weathered at younger ages."

Interview Highlights

On how the body's natural stress response can lead to weathering

Human bodies have evolved, and the reason we haven't gone extinct yet is because when we're faced with an acute, life-threatening challenge, our body automatically activates this release of hormones. And what those hormones do as they flood your body is they increase your heart rate. They increase your breathing rate. They propel oxygenated blood to your large muscles quickly. ... They galvanize fats and sugars from your storage areas of your body into the bloodstream to provide energy towards that ability to fight or flee. ...

That process, when you're fighting or running from the cheetah, is a wonderful adaptive process that is designed to last about three minutes. ...

The problem in the modern world is ... a lot of [stress] is simply everyday life: Coming home after night shift work and having to stay wide awake and vigilant so you don't forget to get off your bus for the next bus to go home. Trying to get your kids up for school at five in the morning so you can also get to work. ... This means that the stress hormones are chronically flooding your body. The fats and sugars that you catapulted into your bloodstream for energy are constantly flooding your body.

It means your heart rate is up, [and] like any other over-exercised muscle, you'll start to get an enlarged heart. You'll start to get hypertension from pushing so much blood through certain arteries and veins to get your heart rate going and your breathing going. If you were pregnant, you might lose your baby, because it's actually probably more adaptive if you're in fight or flight to not be carrying a baby. But even if you don't lose the baby, you'll shunt nutrients away from it because they can't be spent on the growing baby. And so your baby may be born low birth weight or growth retarded because it hasn't been well nourished in the womb.

On why middle- and upper-class "stress" isn't the same

[More affluent people] can take vacations. They can hire people to do their housework or even order their food to be delivered. It's not a relentless day in, day out. They still have many choices. They still have time to relax. They're not dealing with the stereotypical racism aspect that also can activate this process. So the problem is "stress" is this very diffuse term. And we think of it as something you can just meditate your way out of or take a vacation or a break. Many people in our country can't even take a break during working hours.

On improving maternal mortality rate

Maternal mortality still keeps going up. ... But I think more and more people are understanding that systematic racism in the medical care system is part of the problem. There are ways around it, whether those ways are having birth attendants who are doulas or midwives, rather than physicians; having your birth at home. Ways where you will be less stressed during and feel safer during the birth can make a difference. But at this point we don't have enough midwives or doulas or maternity-care providers at all. We have about one maternity-care provider per 15,000 births, and that's not spread evenly over the country. ... So we also have to do things that get more people trained, and trained not just as OB-GYNs but as midwives and doulas.

On studying why Latin American immigrants, such as those from Mexico, have worsening health the longer they're in the U.S.

You're a fish out of water. If you've been raised in an immigrant family from Mexico, and then you're moving into predominantly white, American, affluent and well-educated communities and institutions, ... where you don't share the same assumptions or background, where the people you're working with don't appreciate all you've been through, where you're having to always be on your guard and manage how you portray yourself or present yourself to try and not fulfill stereotypes that you think people you're working with or going to school with might have about you. ....

And that means you're at a certain level of vigilance and looking for cues everywhere of whether you belong, whether you're welcome, whether you're going to be subject to what many people call microaggressions. ... Those experiences themselves can cause weathering.

On how social mobility of minorities doesn't mean less stress

[Our health is] an indicator of ... the context that we live in, of a society that is racist, oppressive, class conscious. ... We won't solve health inequalities between Blacks and whites or Latinx and whites or other groups simply by getting people more education or higher incomes. This chronic stress arousal is more likely in those kinds of unsupportive environments than ... the more supportive environments, if you stick with your own group. Weathering is not against social mobility, it's not for segregation, it's for non-erasure. It's for seeing and recognizing what is really happening, and what it does to you biologically, and realizing if we want to eliminate health disparities or promote health equity, we have to attend to what's happening in these different settings.

Audio interview produced and edited by: Heidi Saman and Thea Chaloner. Audio interview adapted for NPR.org by: Bridget Bentz, Molly Seavy-Nesper and Carmel Wroth.