LITCHFIELD, Conn. — About 45 million U.S. adults, or 18% of Americans over age 18, didn’t fill a prescription last year because of high drug costs, according to nonprofit group Prescription Justice.

The U.S. percentage of adults forgoing prescriptions because of cost is nine times higher than for adults in the United Kingdom (2%), where drugs are largely covered by national health insurance, Prescription Justice found in an analysis based on data from the Commonwealth Fund’s 2016 International Health Policy Survey of Adults. The survey polled about 2,000 U.S. adults and nearly 27,000 adults overall.

“Americans cannot afford to wait a day longer for drug price relief,” Jodi Dart, executive director of Prescription Justice. “Tens of millions of Americans are not taking medications because of high drug prices. We urge President Trump to keep his campaign promise to stand up to big pharma and bring relief to millions of Americans who are unduly suffering because they can’t afford the vital medications that will help them get better.”

Besides in the United States and the United Kingdom, the percentage of adults not filling prescriptions because of cost in 2016 was 10% in Canada, 9% in Switzerland, 6% in Australia, 6% in New Zealand, 6% in Sweden, 4% in France, 4% in the Netherlands and 3% in Norway, according to Prescription Justice’s study.

In the U.S., this percentage has actually come down. Before the Affordable Care Act went into effect in late 2013 — providing prescription drug benefits for millions who previously lacked coverage — 21% of American adults reported not filling prescriptions because of cost, Prescription Justice noted.

An earlier estimate pegged the number of U.S. adults forgoing a prescription because of cost at 35 million, but that was based on a 2014 Commonwealth Fund survey, which polled adults ages 18 to 64, not including elder Americans age 65 and older, as in the new survey, Prescription Justice added.