Lead author Dr. Stefan Kertesz, an associate professor in the University of Alabama at Birmingham, and colleagues said data from the National Survey on Drug Use and Health indicated 9.4 percent of U.S. adults ages 50-59, and 7 percent of adults ages 35-49, reported drug use other than marijuana sometime in the past year.
The researchers used data from the Coronary Artery Risk Development in Young Adults Study for their analysis involving adults ages 18-30 tracked from 1985 to 2006.
The research team looked specifically at the reported use of hard drugs -- cocaine, amphetamines and opiates -- by 4,301 of the participants and compared them who stopped drug use.
"Fourteen percent of the people in the study reported recent hard-drug use at least once, and of these, half continued using well into middle age," Kertesz said in a statement. "But, most of the drug users in our study were not addicts. They were dabblers who used just a few days a month."
The study, published in the Journal of General Internal Medicine, found older hard-drug users were more likely to report being raised in economically challenged circumstances, in a family that was unsupportive, abusive or neglectful. Those who continued to use lower levels of hard drugs into middle age were roughly five times more likely to die than those who didn't use drugs, the study said.
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