This study provides for the first time a detailed overview of poisoning mortality from alcohol-only, opioid-only, and combined alcohol and opioids by educational attainment and race and ethnicity in US men and women. Large and increasing educational inequalities were found between those with and without a college degree in alcohol-only, opioid-only, and combined alcohol and opioid poisonings, with particularly high mortality in those with a high school degree or less. The relative educational inequalities in alcohol-only, opioid-only, and alcohol and opioid poisonings between racial and ethnic groups over time were also quantified. We find that educational inequalities in poisoning deaths were most pronounced in non-Hispanic White and Black men and women. It appears that these socioeconomic differences in drug and alcohol poisonings have been primarily driven by opioid-only poisonings, which caused 53% of the poisonings studied in 2000, rising to 72% in 2018. Despite a dramatic increase in opioid poisonings, the proportion of poisonings caused by combined alcohol and opioids remained stable.
These findings support previous work by Case and Deaton, which found large inequalities between non-Hispanic White individuals with and without a BA degree in poisoning mortality . They also support more recent findings by these authors that suggest that while gaps in mortality between race and ethnic groups have decreased, inequalities in mortality between educational groups have increased. Our results build on this work and suggest that for poisoning deaths, these widening educational inequalities are occurring both in the adult population overall and within racial and ethnic groups. We have shown growing inequality between educational categories for non-Hispanic Black and White groups for all types of poisoning deaths considered and that the inequalities have grown dramatically between those with a high school degree or less compared to those with a college degree. Additionally, our results suggest that relative educational inequalities in combined alcohol and opioid poisoning mortality may be the largest and increasing the most over time for non-Hispanic Black individuals. Consistent with this, a recent report by the US Substance Abuse and Mental Health Services Administration (SAMHSA) highlights dramatic growth in opioid overdose deaths in Black communities . A number of factors could be driving this, including increased availability of pure heroin, greater presence of potent synthetic opioids such as fentanyl in illicit drug markets, and racial and ethnic and neighborhood disparities in access to medications for treating opioid use disorders [24, 25].
In addition to providing a detailed overview of the poisonings from different substances by race and ethnicity and education, we provide a new method for categorizing both alcohol and combined alcohol and opioid poisonings. This method avoids previous issues noted with the changing of ICD-10 codes F10.0 that has been previously documented . This provides a new methodology for capturing trends in alcohol poisonings that avoids jumps in the data.
We were unable to separate US-born and non-US-born Hispanic individuals; however, there may be key differences between these populations. Prior research shows that non-US-born Hispanic individuals are less likely to use substances and more likely to have lower educational attainment [27, 28], and thus aggregating across these groups could potentially obscure important patterns and trends.
One further limitation is that we were not able to consider a breakdown of the rather heterogeneous, non-Hispanic others group including mixed race and ethnicity, due to the small numbers of poisonings observed in some sub-categories (e.g., alcohol poisonings in those with a BA degree). Although we were unable to draw conclusions about this group from our data, our results for the non-Hispanic other race and ethnicity group are similar to previous findings, specifically, differences in unintentional injury mortality (including poisonings) in Native American and Alaska Native individuals, with these individuals having a rate eight times higher than non-Hispanic Whites for alcohol poisoning . Since these individuals are more likely to be in the high school degree or less educational category , this could explain the disparities in the present study in alcohol-only poisonings between non-Hispanic others with low and high education.
While we did not consider substances other than alcohol and opioids, there are other substances that may be contributing to the pooled drug and alcohol poisonings . Specifically, recent data suggests that a “fourth wave” of the opioid epidemic may have been entered, characterized by substantial co-involvement of opioid poisonings with cocaine, amphetamine, and benzodiazepines in 2019 . One substance that is important to consider in future work is benzodiazepines, which have recently been estimated to be involved in 21% of opioid poisonings. It is unclear whether there are socioeconomic inequalities in these. In this study, we were only able to explore differences by educational attainment and race and ethnicity. Future work should consider other demographic factors, including additional facets of socioeconomic status, specific age groups, and urban vs. rural locations . The results of this study are only applicable to a US context and would not be generalizable to other countries with differing socioeconomic inequalities and access to healthcare. Although our method for defining alcohol poisonings avoids previously documented inconsistencies in the data, this method is yet to be validated by an external expert committee. Finally, there are potential biases in the coding of poisonings, which could lead to an underestimation of the number of opioid poisonings presented in the current analysis . It is also possible that due to stigma, these biases are unequally distributed across groups, for example, individuals with higher socioeconomic status may be less likely to be assigned an opioid poisoning category. It is important to consider in future work how these biases may relate to the under-recording of opioid-only and combined opioid poisonings and how these differ across sociodemographic groups.
Our findings demonstrate the increasing concentration of poisoning deaths among individuals with low socioeconomic status. This may be indicative of specific developments in the opioid crisis as well as societal trends of growing despair. In more recent years, a shift in the opioid crisis has been observed with declining opioid prescription rates, increases in poisoning deaths from illicitly manufactured opioids, and greater presence of opioids mixed with toxic adulterants . This has coincided with increasing exposure to more potent substances such as cheaper synthetic opioids like fentanyl in illicit drug markets. Combined with disparities in access to effective substance use treatment [24, 25], these developments might be driving the increasing concentration of poisoning deaths in lower SES and Black populations we observed. These underlying dynamics of the opioid crisis might explain an increase in opioid-only and combined alcohol and opioid poisonings in lower socioeconomic groups. However, we also find rising alcohol-only poisonings in these groups, which cannot be explained by these mechanisms alone and may instead be a symptom of wider despair in society [15, 34]. Large parts of society at the lower end of the socioeconomic spectrum have experienced increasing levels of economic hardship, job insecurity, uncertainty about the future, and disruptions in the social fabric of their communities [15, 34]. Public health strategies should focus on intervening through a combination of these mechanisms. These include harm reduction strategies such as the provision of safer drug use spaces and expanded access to naloxone , equitable access to effective treatments for opioid use disorders, and a wider health-in-all-policies approach that encompasses policies on affordable or universal health care and strengthening of social welfare systems to decrease despair. Our finding that those with low education have dramatically rising poisoning death rates is also important to consider in the context of educational attainment patterns by race and ethnicity. In 2017, nearly half (46%) of Black Americans aged 25 or older had only a high school degree or less compared to one-third (34%) of White Americans  and thus might be disproportionately affected by these recent trends. Finally, the COVID-19 pandemic appears to have exacerbated mortality trends. Deaths from drug poisonings have increased further , especially in Black populations , and this trend has corresponded with increases in socioeconomic  and racial and ethnic  inequalities in mortality that are directly and indirectly related to COVID-19. Therefore, it is likely that there will be further widening of socioeconomic inequalities in poisoning mortality with differences across US racial and ethnic groups.