Age and generational patterns of overdose death risk from opioids and other drugs

Abstract

The ongoing substance misuse epidemic in the United States is complex and dynamic and should be approached as such in the development and evaluation of policy¹. Drug overdose deaths (largely attributable to opioid misuse) in the United States have grown exponentially for almost four decades, but the mechanisms of this growth are poorly understood². From analysis of 661,565 overdose deaths from 1999 to 2017, we show that the age-specific drug overdose mortality curve for each birth-year cohort rises and falls according to a Gaussian-shaped curve. The ascending portion of each successive birth-year cohort mortality curve is accelerated compared with that of all preceding birth-year cohorts. This acceleration can be attributed to either of two distinct processes: a stable peak age, with an increasing amplitude of mortality rate curves from one birth-year cohort to the next; or a youthward shift in the peak age of the mortality rate curves. The overdose epidemic emerged and increased in amplitude among the 1945-1964 cohort (Baby Boomers), shifted youthward among the 1965-1980 cohort (Generation X), and then resumed the pattern of increasing amplitude in the 1981-1990 Millennials. These shifting age and generational patterns are likely to be driven by socioeconomic factors and drug availability, the understanding of which is important for the development of effective overdose prevention measures.

Figure 1.

Hexamaps illustrating the age and generational structure of overdose deaths from 1979 through 2017. (A) Schematic of the components of the hexamap, showing hexagonal data points as defined by age, period and cohort, arrayed along axes at 60 degree angles, and (B) Hexamap of the overall epidemic of overdose deaths where the colors indicate the mortality rates as shown in the legend. The top dashed line is drawn along the isoline of cohort = 1945, and the bottom dashed line is drawn along the isoline of age = 18. These dashed lines represent the boundaries of the wedge-shaped epidemic. [A = age, Y = calendar year, C = cohort].

Figure 2.

Rapid rise in age-specific overdose mortality curves by birth-year cohort. (A) and (B) show the annual and the cumulative overdose mortality rates per 100,000 persons by birth-year cohorts, respectively. Each line represents a specific birth-year cohort, with the order of birth-year cohorts shown as a color spectrum, earlier cohorts to more recent cohorts represented by blue to red. Overdose mortality data from 1979-2017 are displayed. Decennial birth-year cohorts are highlighted and labeled. See Supplementary Movie 1 for the mortality rate curves for each successive cohort.

Figure 3.

Birth-year specific overdose mortality follows Gaussian curves. (A) Observed and projected age-specific overdose mortality rate curves, showing six representative (decennial, 1940-1990) birth-year cohorts. Shown are the observed data (points) and the fitted/projected Gaussian curve approximations (solid lines with 95% confidence bounds). The order of birth-year cohorts is shown as a color spectrum, from earlier cohorts to more recent cohorts represented by blue to red. The bottom panels show the parameter estimates (black line) and 95% confidence intervals (orange colored area) for: (B) The peak age of overdose mortality (μ), (C) the peak mortality rate amplitude (α), and (D) the Gaussian curve width (σ).

Figure 4.

Three phases of overdose deaths revealed by plotting of the estimated peak age of overdose mortality versus the estimated peak amplitude of the overdose mortality rate, for all fifty-one birth-year cohorts 1940-1990 (A). Phase I – increasing peak mortality rates among Baby Boomer birth-year cohorts (1945-1964), Phase II – youth-ward shift among Generation X birth-year cohorts (1965-1980), and Phase III – increasing mortality rates among Millennial birth-year cohorts (1981-1990). Confidence bounds are provided in the supplemental materials Extended Data 3. These three generational phases correspond to the previously recognized three opioid drug waves of prescription opioids, heroin, and fentanyl (B). For each drug wave, the phase with the highest mortality rate in that drug wave is marked with an asterisk (*).