July 23 (UPI) -- Wealth may not buy happiness, but it could be the key to a long life, according to a study published Friday by JAMA Health Forum.
In a model comparing two family members whose net worth differed by $139,000 by their late 40s, the one with the higher net worth was 13% more likely to be alive 24 years later than a relative with less personal wealth, the data showed.
In addition, for every $50,000 of net worth accumulated at midlife -- defined as late 40s for the purposes of the study -- a person could improve their odds of being alive for another 24 years by about 5%, the researchers said.
Moreover, siblings or twins in the study population with more wealth tended to live longer than their siblings or twins with less.
This suggests that wealthier people may live longer because of personal riches, not simply due to genetics, according to the researchers.
Although this is good news for people with substantial income and savings, it also indicates that income inequality may lead to health inequality, the researchers said.
"Far too many American families are living paycheck to paycheck with little to no financial savings to draw on in times of need -- at the same time, wealth inequality has skyrocketed," study co-author Greg Miller said in a press release.
Those who have less personal wealth likely also have reduced access to quality healthcare and an increased risk for chronic conditions such as heart disease and diabetes that limit their ability to earn money and shorten their life expectancy, the researchers found.
"Our results suggest that building wealth is important for health at the individual level, even after accounting for where one starts out in life," said Miller, a professor of psychology at Northwestern University's Institute for Policy Research in Evanston, Ill.
Between 1970 and 2018, incomes for the wealthiest people in the United States increased by 64%, according to data from Pew Research.
Over the same period, middle- and low-income households saw their earnings increase by about 45%.
Income growth was particularly robust for those among the top 5% of earners nationally, and more "tepid" for the remaining 95%, the Pew data showed.
Such income inequality suggests that people in the "lower rungs of the economic ladder may experience diminished economic opportunity," according to Pew.
For this study, Miller and his colleagues analyzed the midlife net worth of adults and their mortality rates 24 years later, using data from the Midlife in the United States project, an ongoing analysis of aging nationally.
The full study population included 5,400 adults, roughly 2,500 of whom were part of sibling or twin pairs.
Higher net worth was associated with a 6% lower mortality risk from an average age of roughly 47 through 24 years later, the data showed.
Even after removing study participants with heart disease or cancer from the analysis, the within-family association between wealth and longevity remained.
"The within-family association provides strong evidence that an association between wealth accumulation and life expectancy exists," study co-author Eric Finegood said in a press release.
"[That's] because comparing siblings within the same family to each other controls for all of the life experience and biology that they share," said Finegood, a postdoctoral fellow at Northwestern University's Institute for Policy Research.