About 95 percent of the relationship between intelligence and longevity is explained by genetic influences on both traits, researchers reported July 26 in the International Journal of Epidemiology. The study was somewhat limited in that most of the participants took intelligence tests during middle age, rather than in their youth. By that time, the IQ results might be skewed by the cognitive decline of aging.

Nevertheless, the researchers say, the results suggest that brighter people don’t just live longer because they make healthier choices, or make more money that affords them better health care. Rather, they live longer because their genetic makeup favors both smarts and a long life.

“We found that the small relationship between intelligence and life span was almost all genetic,” said study researcher Rosalind Arden, a research associate at the London School of Economics and Political Science.