Illegal drug users experience mortality rates greater than those among the general population1. In the United States and Europe, mortality among drug users has been estimated to be at least nearly seven times that of the general population2345. While the causes of mortality among drug using populations are varied and include trauma 6 and HIV/AIDS7, overdose is an important contributor to mortality in this group 8910. In 2003, non-medically related drug toxicity was the tenth leading cause of mortality in New York City (NYC) 11.

The overdose experiences of heroin users have been extensively studied 1213141516. Furthermore, the development of effective interventions to reduce accidental opiate overdose death, such as the provision of naloxone and the creation of safe injecting spaces have also been described 171819. Several review articles have been published synthesizing what we know about opiate overdose and its related mortality 202122. However, a number of studies have shown that multi-drug use contributes dramatically to overdose death 152324, and in several cities, cocaine is suspected to be a considerable contributor to accidental overdose mortality9.

While cocaine overdose is prevalent, there is a paucity of research that has examined the relative contribution of cocaine to overdose mortality. One of the few studies that examined fatal cocaine overdoses found that the route of administration for over 85% of decedents was injection, over half of the deaths occurred during a weekend and 41% of deaths occurred in the presence of others 25. Therefore, although cocaine is probably an important contributor to overdose deaths in many urban areas26, there is little research that has systematically explored the characteristics of decedents whose death is attributed to cocaine overdose9.

In NYC, previous studies have documented the importance of polydrug overdose to overall overdoses 9 and racial/ethnic disparities in overdose fatalities 10. However, there have been no papers of which we are aware that have studied the factors associated with cocaine vs. opiate-related overdoses in NYC or elsewhere. While the importance of polydrug overdose cannot be understated, as interventions for the prevention of fatal overdose become more targeted, such as naloxone for opiate overdoses 171922272829, a clearer understanding of the importance of opiate and cocaine fatal overdose as distinct events increase. In this study, we examined all accidental overdose deaths in NYC between 1990 and 2000 to characterize differences in cocaine- and opiate-related drug overdoses. In NYC, mortality related to drug overdose is of substantial public health concern 30. Therefore, the purpose of this study was to explore the epidemiologic correlates of cocaine- and opiate only related overdose. Furthermore, we sought to examine whether these correlates were different between those decedents who fatally overdosed with both cocaine and opiates, cocaine alone, and opiates alone. Understanding these epidemiologic differences may prove critical in the development of successful, innovative interventions and prevention messages that can reduce overdose-related mortality.

From 1990 through 2000, the OCME reported 8,774 fatal overdose deaths among New Yorkers aged 15–64 involving cocaine and/or opiates. Characteristics of total overdose, cocaine only overdose and opiate only overdose decedents in NYC are shown in Table 1. Among all overdose deaths during the study period, 2,392 (27.3%) were attributed to cocaine only and 2,825 (32.2%) were attributed to opiate only overdose.

Of the 8,774 fatal overdoses involving cocaine and/or opiates that occurred in NYC from 1990 to 2000, 79.4% were male, 33.6% were White, 36.9% were Black, and 29.5% were Hispanic. Nearly 75% of the decedents were younger than 45 years old at the time of death. Among the five boroughs of NYC, Manhattan had the largest proportion of accidental overdose deaths with 32.0% occurring in that borough; 27.3% of the total overdose fatalities occurred in Brooklyn, 24.1% in the Bronx, and smaller proportions in Queens (14.6%) and Staten Island (2.0%). While cannabis was detected in only 8.0% of the decedents at the time of death, alcohol was found in almost half (42.2%) of fatal overdoses. Most accidental overdose deaths occurred in a residence (75.7%). Almost one half of all overdose deaths occurred during a weekend (47.0%).

The total number of accidental overdose deaths in NYC among 15–64 year olds related to cocaine and/or opiates increased from 1990 to 1993, plateaued, and then exhibited a steady decline until 1999 (Figure 1). A slight increase in the total fatal overdoses in this population was seen in 2000. While the number of cocaine only overdose deaths remained relatively constant from 1990–2000 (χ² test for trend, p = 0.18), opiate only deaths saw a small, but steady increase during the same time period (χ² test for trend, p = 0.10).

Figure 2 shows the trends in the proportion of total accidental overdose deaths that involved cocaine and/or opiates. While the absolute number of cocaine only fatal overdoses remains constant from 1990–2000, the proportion of overdoses attributed to cocaine-only declined during the 11-year period from 29.2% to 23.6% (χ² test for trend, p = 0.07). Over the same period, the proportion of opiate only fatal overdoses rose from 30.6% in 1990 to 40.1% in 2000 (χ² test for trend, p=<0.001).

The descriptive characteristics of the three groups of decedents are shown in Table 1. Among women overdose decedents, 34.9% were classified as cocaine-only compared to 25.3% among men with a fatal overdose. This trend was reversed for opiate-only and cocaine and opiate overdose deaths. Among Black overdose decedents 41.7% were cocaine only, 20.7% opiate only, and 37.6% cocaine and opiate fatal overdoses. For Whites who fatally overdosed, the trend is different, with the largest proportion categorized as opiate (42.1%); the largest proportion of Hispanic decedents was cocaine and opiate overdose deaths (43.3%). A dose response was seen with respect to age with likelihood of cocaine only overdose among all overdose deaths, increasing with age (p < 0.001). Borough of death was associated with all three categories, with cocaine only and opiate only overdose fatalities occurring in the largest proportion for decedents residing in all boroughs except Staten Island. The absence of either cannabis (27.8% versus 20.6% for cannabis detected) or alcohol (32.8% versus 0.2% for alcohol detected) was associated with an increased likelihood of a cocaine only overdose (p < 0.001) among those fatally overdosing in NYC. All three groups had associations with location of overdose.

The results of multivariate logistic regression models for the three categories of overdose decedents are shown in Table 2. The first model compared those with a cocaine only overdose death to those with a fatal overdose in the two other categories. Decedent males were less likely to experience a cocaine only overdose than females (adjusted OR = 0.77, 95% CI 0.68–0.87). Furthermore, both Black (adjusted OR = 3.23, 95% CI 2.85–3.67) and Hispanic (adjusted OR = 1.37, 95% CI 1.19–1.58) overdose fatalities were more likely to be from cocaine only, compared to Whites. Decedents at older ages were more likely to have fatally overdosed from cocaine only than from some other drug(s). No associations were found between borough of death, cannabis detection, or year of death and cocaine only overdose. However, a negative association was found between alcohol presence at autopsy and cocaine only fatal overdose.

The second model shown in Table 2 examined opiate only fatal overdoses compared to the other two groups. Here, males were more likely to experience an opiate only than any other drug combination (adjusted OR = 1.22, 95% CI 1.08–1.38). Contrary to what was found with respect to cocaine only overdose fatalities, for drug decedent New Yorkers, Whites were more likely to have an opiate only than Hispanics or Blacks. After adjustment for other covariates, the negative association with age all but disappeared. When borough of death was examined (borough of Manhattan used as the referent category), those New Yorkers fatally overdosing in Brooklyn (adjusted OR = 1.46, 95% CI 1.29–1.65) or Queens (adjusted OR = 1.34, 95% CI 1.15–1.55), decedents were more likely to have had an opiate only overdose. Alcohol detection at autopsy was associated with a nearly 40% increase in the likelihood that a New Yorker fatally overdosed on opiates-only, compared to other fatal drug combinations.

No gender or race associations were found when cocaine and opiate fatal drug overdoses were modeled. Decedents over 45 years old were less likely to have overdosed on a combination of cocaine and opiates. When compared to Manhattan, decedent in Brooklyn, Queens, or Staten Island were less likely to have had an overdose attributed to cocaine and opiates. Both cannabis and alcohol detection was associated with an increased likelihood of overdose death from cocaine and opiates, compared to overdose death attributed to other drug combinations.

Table 3 shows the results of the single multinomial regression model in which cocaine only is directly compared to opiate only overdose deaths. Male decedents were less likely to have overdosed on cocaine only than opiates-only. Additionally, Blacks who fatally overdosed were nearly five times more likely to have done so from cocaine only; Hispanics were 1.5 times more likely. Age at death greater than 24 was associated with an increased likelihood that the fatal overdose was attributed to cocaine only rather than opiates-only. Overdose death in Brooklyn was more likely a result of opiates-only than cocaine only. Fatal overdoses that occurred outside were more likely to have been attributed to cocaine only than opiates only. Alcohol detected at autopsy was half as likely among those who overdosed on cocaine only. There was no significant association observed for overdose deaths from cocaine only with respect to year of death.