Fentanyl overdose deaths are surging among seniors, particularly in cases where the powerful opioid is mixed with stimulants like cocaine or methamphetamine, a new study says.

Fentanyl-stimulant overdose deaths skyrocketed by an astonishing 9,000% during the past eight years, approaching rates found in younger adults, researchers reported Saturday at an American Society of Anesthesiologists' meeting in San Antonio, Texas.

"A common misconception is that opioid overdoses primarily affect younger people," lead researcher Gab Pasia, a medical student at the University of Nevada-Reno School of Medicine, said in a news release.

"Our analysis shows that older adults are also impacted by fentanyl-related deaths and that stimulant involvement has become much more common in this group," Pasia said. "This suggests older adults are affected by the current fourth wave of the opioid crisis, following similar patterns seen in younger populations."

America's opioid epidemic has unfolded in four distinct waves, researchers explained in background notes.