Net worth at midlife is associated with longevity among U.S. adults, according to a study published online July 23 in JAMA Health Forum.

Eric D. Finegood, Ph.D., from the Institute for Policy Research at Northwestern University in Chicago, and colleagues used data from the Midlife in the United States study to examine the association between net worth at midlife and subsequent all-cause mortality in individuals as well as within siblings and twin pairs. The analysis included 5,414 participants with 24 years of follow-up.

The researchers found that higher net worth was associated with lower mortality risk (hazard ratio [HR], 0.95; 95 percent confidence interval [CI], 0.94 to 0.97; P < 0.001). A similar within-family association was seen between higher net worth and lower mortality among siblings and twin pairs (2,490 people; HR, 0.94; 95 percent CI, 0.91 to 0.97; P = 0.001), suggesting that the sibling or twin with more wealth tended to live longer than their co-sibling or co-twin with less wealth. Within-family estimates of the net worth-mortality associations were similar for siblings (HR, 0.94; 95 percent CI, 0.90 to 0.97; P = 0.002), dizygotic twins (HR, 0.94; 95 percent CI, 0.86 to 1.02; P = 0.19), and monozygotic twins (HR, 0.95; 95 percent CI, 0.87 to 1.04; P = 0.34), although the precision of estimates was reduced among twins.

"Discordant sibling analyses suggested that this association is unlikely to be simply an artifact of early experiences or heritable characteristics shared by families," the authors write.