In this study, researchers collected data from 3,109 counties within 49 states (excluding Alaska) and the District of Columbia from January 2001 to December 2017 comprising a total of 52,853 county-years. The study’s primary exposure was specified as state adoption of Medicaid expansion under the Affordable Care Act (ACA). The researchers developed an indicator to measure the proportion of each calendar year during which Medicaid expansion went into effect; assigning a value of 0 in years before Medicaid expansion, a value between 0 and 1 in the year in which Medicaid went into effect, and value of 1 for all subsequent years.
The primary endpoint was defined as the annual county-level mortality from overdoses involving any opioid, natural and semisynthetic opioids, methadone, heroin, and synthetic opioids other than methadone, derived from the National Vital Statistics System multiple-cause-of-death files. The secondary endpoint was stipulated as fatal overdoses involving all drugs. They used hierarchical Bayesian Poisson models to estimate overdose deaths and performed data analysis from April 2018 to July 2019.
According to the results of the study, Medicaid expansion was associated with a 6% lower rate of total opioid overdose deaths juxtaposed with the rate in non-expansion states (relative rate [RR]=0.94; 95% credible interval [CrI], 0.91 to 0.98). Moreover, the results showed that Medicaid expansion was correlated with a 11% lower rate of death involving heroin, and 10% lower rate of death involving synthetic opioids other than methadone compared with counties in non-expansion states.
However, the findings did show that Medicaid adoption was associated with a 11% increase in methadone-related overdose deaths in expansion states (RR=1.11; 95% CrI, 1.04 to 1.19). The researchers noted that an association between Medicaid expansion and deaths involving natural and semisynthetic opioids was not well supported (RR=1.03; 95% CrI, 0.98 to 1.08).
— Magdalena Cerda (@Magda_Cerda) January 10, 2020
“These findings add to the emerging body of evidence that Medicaid expansion under the ACA may be a critical component of state efforts to address the continuing opioid overdose epidemic in the United States,” the study authors wrote in their summation.
They added that: “As states invest more resources in such efforts, attention should be paid to the role that health coverage expansions can play in reducing opioid overdose mortality, potentially through greater access to medications for opioid use disorder.”
— Corey Davis (@coreysdavis) January 10, 2020
An exciting finding: Medicaid expansion decreased opioid overdose deaths. But I'm not sure I follow the authors' model. Any thoughts from methodologists? I'm a bit nervous when I see a complex specification without specification sensitivities or fit tests. https://t.co/nBpNM5vQlJ
— Alex Gertner (@gertner_alex) January 10, 2020