Urban scaling of opioid overdose deaths in the USA: a cross-sectional study in three periods between 2005 and 2017

Abstract

Objectives: To describe the association between population size, population growth and opioid overdose deaths-overall and by type of opioid-in US commuting zones (CZs) in three periods between 2005 and 2017.

Settings: 741 CZs covering the entirety of the US CZs are aggregations of counties based on commuting patterns that reflect local economies.

Participants: We used mortality data at the county level from 2005 to 2017 from the National Center for Health Statistics.

Outcome: Opioid overdose deaths were defined using underlying and contributory causes of death codes from the International Classification of Diseases, 10th revision (ICD-10). We used the underlying cause of death to identify all drug poisoning deaths. Contributory cause of death was used to classify opioid overdose deaths according to the three major types of opioid, that is, prescription opioids, heroin and synthetic opioids other than methadone.

Results: Opioid overdose deaths were disproportionally higher in largely populated CZs. A CZ with 1.0% larger population had 1.10%, 1.10%, and 1.16% higher opioid death count in 2005-2009, 2010-2014, and 2015-2017, respectively. This pattern was largely driven by a high number of deaths involving heroin and synthetic opioids, particularly in 2015-2017. Population growth over time was associated with lower age-adjusted opioid overdose mortality rate: a 1.0% increase in population over time was associated with 1.4% (95% CI: -2.8% to 0.1%), 4.5% (95% CI: -5.8% to -3.2%), and 1.2% (95% CI: -4.2% to 1.8%) lower opioid overdose mortality in 2005-2009, 2010-2014, and 2015-2017, respectively. The association between positive population growth and lower opioid mortality rates was stronger in larger CZs.

Conclusions: Opioid overdose mortality in the USA was disproportionately higher in mid-sized and large CZs, particularly those affected by declines in population over time, regardless of the region where they are located.

Keywords: epidemiology; public health; substance misuse.

Figure 1

Boxplots for age-standardised opioid mortality rate in groups of CZs by decile of the population in three periods. Population decile 1 has 75 CZs, 90% of which have less than 10 000 people. The other deciles have 74 CZs each. CZs, commuting zones; NCHS, National Center for Health Statistics.

Figure 2

Opioid deaths in US commuting zones (CZs) in three periods: 2005–2009, 2010–2014 and 2015–2017. The line represents the regression line of the association between opioid overdose death counts and population counts. Red CZs are those with positive residuals (death counts are larger than predicted by the model) and green CZs are those with negative residuals (death counts are smaller than predicted).