While high risk prescription opioid use has declined over the past decade, nearly 1 in 10 adults in the United States remain at risk for opioid overdose, according to a national sample of prescription claims.

Researchers at the University of Southern California School of Pharmacy and the University of Illinois at Chicago examined a representative, 5% sample of anonymized data drawn from individual prescription claims from 2011 through 2016. They found that, overall, the use of opioids may be tapering: 30% of people filled at least one opioid prescription in 2011 compared to 27.2% in 2016.

However, they detected higher rates of risk among older consumers, who tended to use Medicare for payment. Data showed that these consumers were also more likely than their younger counterparts to have multiple prescribers and purchase from multiple pharmacies. While opioid use declined by 36.2% among people ages 18 to 35, use declined by only 6.7% among those 65 years or older.

“Future clinical studies and policy interventions,” the authors suggested, “should consider targeting older adults with Medicare Part D, including those using a single pharmacy to fill their opioid prescriptions.”

The study was published in Pharmacoepidemiology and Drug Safety.