Corrected US opioid-involved drug poisoning deaths and mortality rates, 1999-2015.

BACKGROUND AND AIMS: Most prior estimates of opioid-involved drug poisoning mortality counts or rates are understated because the specific drugs leading to death are frequently not identified on death certificates. This analysis provides corrected national estimates of opioid and heroin/synthetic opioid-involved counts and mortality rates, as well as changes over time in them from 1999 to 2015.
METHODS: Data on drug poisoning deaths to US residents from 1999 to 2015, obtained from the Centers for Disease Control and Prevention (CDC) Multiple Cause of Death (MCOD) files, were used with the drugs involved in fatal overdoses imputed when not identified on the death certificates.
RESULTS: The official CDC figure that 33 091 drug deaths involved opioids in 2015 is an undercount, with the actual number being approximately 39 999. Corrected counts and rates of any opioid and heroin/synthetic opioid-involved drug deaths are 20-35% higher in every year than reported figures. The corrections almost always raise the changes estimated to have occurred since 1999, with the largest differences observed in 2011 for any opioids (5677 deaths and 1.7 per 100 000) and in 2015 for heroin/synthetic opioids (3228 deaths and 1.0 per 100 000). However, percentage growth since 1999 is sometimes slower when based on corrected rather than reported fatality data, and with sensitivity to the choice of base years.
CONCLUSIONS: Death certificate reports understate the prevalence of and changes over time in opioid and heroin/synthetic opioid-involved drug mortality in the United States. Adjustments imputing the drugs involved for cases where none are identified on the death certificates are likely to provide more accurate estimates.