70,000 opioid-related overdose deaths in US unaccounted for since 1999, study says

The opioid crisis plaguing the U.S. may be even worse than health officials previously thought, with tens of thousands of opioid-related deaths possibly going unreported from 1999 to 2015.

Death certificates in at least five states — Alabama, Indiana, Louisiana, Mississippi, and Pennsylvania — did not specify the type of drugs used in 35 percent of overdose deaths, a team at the University of Pittsburgh Graduate School of Public Health revealed in a recent study. Pennsylvania had the highest number of unspecified overdose deaths.

Researchers believe at least 70,000 overdose deaths recorded across the U.S. over the span of roughly 16 years were related to opioids.

"States may be greatly underestimating the effect of opioid-related overdose deaths because of incomplete cause-of-death reporting, indicating that the current opioid overdose epidemic may be worse than it appears," the researchers concluded in an article published in the journal of Public Health Reports.

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A study published by the Society for the Study of Addiction in February came to a similar conclusion, estimating opioid-related deaths are 20-to-35 percent higher per year than what's reported.

Researchers studied cause-of-death codes (International Classification of Diseases) implemented by the National Center for Health Statistics (NCHS). In some cases, medical examiners or coroners can identify a specific substance used. If they are unsure, they can mark the cause of the overdose "unspecified."

"The missing information on drug types leads to underestimating deaths from specific drugs, such as opioid-related deaths," authors of the study explained.

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Researchers found states with a centralized medical examiner system are more likely to label specific drugs related to an overdose death.

"The major advantages of a statewide medical examiner system are the quality of death investigations and forensic pathology services and their independence from population size, county budget variation, and politics," according to the National Center for Biotechnology Information. "Certification of death is accomplished by highly trained medical professionals who can integrate autopsy findings with those from the crime scene and the laboratory."

In order to have a more accurate count, researchers suggest updating NCHS death codes and encouraging states to have more organized reporting systems.

In 2016, more than 63,000 drug overdose deaths were reported — and about two-thirds (42,000) were caused by opioids, according to the Centers for Disease Control and Prevention. On average, the opioid crisis is killing at least 115 people in the U.S. each day.