Washington, D.C. ? America’s drug abusers are going gray.

The proportion of people admitted to treatment for drug abuse who are aged 50 or over nearly doubled between 1992 and 2008, a new government study says.

Alcohol is still the leading cause of admissions in this age group, but sharp increases were noted in those needing treatment for heroin, cocaine and marijuana, the Substance Abuse and Mental Health Services Administration reports today.

“These findings show the changing scope of substance abuse problems in America,” agency administrator Pamela S. Hyde said in a statement. “The graying of drug users in America is an issue for any programs and communities providing health or social services for seniors.”