Adults who were raised in the poorest homes scored the worst on their initial cognitive tests, and as expected with age, mental sharpness dropped as people aged.
But among African-Americans, rates of decline were slowest in people who remembered being hungry "sometimes," "often" or "always" as kids and who were thinner than average as older adults, the researchers report today in the journal Neurology. Childhood hunger and body size didn't make a cognitive difference in Caucasians.
"We expected it to come out the other way, that childhood adversity would be related to a faster rate of decline," Barnes said. "We actually found it was protective."
It's possible that calorie-restriction early in life helped cushion the brain from later aging, in line with research that has linked eating less with longer lifespans. But Barnes suspects that non-biological explanations are more likely.
Very few white people in the study reported extreme adversity as children, for one thing, possibly making the sample size too small to detect any relationships in that group.
As for the African-Americans, those who were still alive in their 60s, 70s, 80s and beyond likely represent the hardiest members of a population that came of age before the civil rights movement when there were few opportunities available to them.
"One of the things we know is that African-Americans live sicker and die younger than Whites," said Tené Lewis, a psychosocial epidemiologist at Emory University's Rollins School of Public Health in Atlanta. "When you get to age 65, which is the baseline in the new study, you're already dealing with a heartier African-American population. These are people who, no matter what you throw at them, are particularly resilient."
Trauma and neglect early in life have been linked to all sorts of long-lasting negative health outcomes, Lewis said, including poor heart health, weak immune systems, and high rates of depression.
By exposing a group of people who have overcome adversity and relatively maintained their cognitive health, the new study raises questions about why some people suffer as a result of early stress while others emerge with resilience. Scientists still don't know what puts people into one group or the other.
"I think the big-picture take-home message is that early experiences matter," Lewis said. "But we're not quite sure how or why."