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In 2004, a study titled “The Long Arm of Childhood” found that whether children were rich or poor could influence their health in adulthood. Now a new paper out in the Proceedings of the National Academy of Sciences (PNAS) suggests that childhood has an even longer arm, reaching well into old age. Someone’s economic status as a child, this study suggests, could influence his or her memory and brain health after age 50.

The study’s authors looked at a database of 24,066 people over 50 whose cognitive functioning had been measured every two years from 2004 to 2015, primarily through tests of their verbal memory and fluency. To determine the participants’ level of childhood disadvantage, the authors examined factors such as how many books they had in their home when they were 10, what their parents’ occupations were, and whether their house had a toilet inside and running water.

It turned out that those who had grown up in the wealthier homes were sharper, mentally, in old age. Compared with the people who were least advantaged growing up, people who were most advantaged remembered, on average, 1.27 more words from a list of 10 that was read to them, and when asked to name as many animals as they could think of in a minute, they were able to name an average of five more animals.

It might seem like this could be explained by the fact that the wealthier kids simply got better jobs and became wealthier, healthier adults, but that’s not quite the full picture. The participants’ level of education and jobs throughout their adulthood partly, but not entirely, ameliorated the effect of a poor upbringing on their cognitive skills in old age. The authors conclude that there seem to be three ways childhood poverty might be affecting the brain in adulthood, and they’re not mutually exclusive.

First, there’s the latency model, or the idea that more cognitive stimulation in childhood leads to more advanced brain development later on. Kids in wealthy families might be sent to computer camp, for example, while those in poorer families do less enriching things, such as watch TV. And wealthy families might be more likely to have time to do things such as ask their kids questions or read them books.

“The brain architecture is much more complex if you are stimulated,” says Marja Aartsen, a professor at the Oslo Metropolitan University in Norway and the lead author of the study. “If the architecture is more complex, there are more connections between all the neurons.” Those extra connections come in handy when some of them begin to die off.

Then there’s the pathway model, or the idea that people who grow up wealthier end up going to better colleges, getting better jobs, and generally living less stressful, more enriching lives that protect brain health. In essence, being a rich kid puts you on a pathway to cultivating a healthier brain.

Finally, there’s the cumulative model, which suggests that all the difficult things that happen to poor kids—the so-called adverse childhood experiences, such as neglect or substance abuse—compound one another and lead to worse academic performance, and eventually to cognitive decline.

In the new study’s results, all these factors might be working together. “I found it interesting that they had data that could support all the models,” says Susan A. Everson-Rose, a professor of medicine at the University of Minnesota who has also studied the topic but was not involved with the PNAS study. “It makes a lot of conceptual sense to me.”

Past studies found that socioeconomic conditions in childhood can influence the level of verbal skills and executive functioning that people have when they enter old age. A person’s economic status in adulthood can affect brain health and cognitive functioning in old age as well. The idea that’s now emerging about memory loss is that a problem often thought of as purely related to old age is actually a lifelong process that begins in childhood.

“Epidemiological research in cognitive aging highlights an intuitive yet oftentimes overlooked aspect of brain aging: It is lifelong,” said Emily Greenfield Cohen, an associate professor of social work at Rutgers, in an email.

Surprisingly, in this study, the more advantaged groups had a higher level of cognitive skills, but also a faster decline of their cognitive faculties later in life—something not all research on this topic has found. This could be because, since wealthier people appear to have healthier brains, they might not start to lose their memories until they’re seriously afflicted with dementia or Alzheimer’s. Or they might already be in the early stages of Alzheimer’s, but simply not show symptoms of it right away. Once their cognitive decline begins, the rate might be precipitous compared with that of everyone else. People who grew up wealthy might be “at a higher level of functioning until they are close to death, and then it goes down very fast,” says Aartsen.

It’s thought that people who grew up richer might have more “cognitive reserve,” or resilience and health of the brain that come from living a more stimulating life. Despite this overall advantage, though, there appears to be a time when the wealthier participants’ cognitive reserve can no longer compensate for the loss of neurons that aging brings. “If their cognitive functioning was higher, they had further to fall,” Everson-Rose says.

The authors close their paper with a call for childhood interventions aimed at preventing aging-related cognitive decline. To protect against these effects, poor children should be steered into higher education, they say, and in general be lifted out of poverty. The goal is to stave off cognitive decline as long as possible, even though it might be rapid when it eventually does come.

That way, the arm of childhood would still be long, but its sweep would be more equitable.

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