What explains the association between neighborhood-level income inequality and the risk of fatal overdose in New York City?

Accidental drug overdose is a substantial cause of mortality for drug users. Using a multilevel case-control study we previously have shown that neighborhood-level income inequality may be an important determinant of overdose death independent of individual-level factors. Here we hypothesized that the level of environmental disorder, the level of police activity, and the quality of the built environment in a neighborhood mediate this association. Data from the New York City (NYC) Mayor's Management Report, the NYC Police Department, and the NYC Housing and Vacancy Survey were used to define constructs for the level of environmental disorder, the level of police activity and the quality of the built environment, respectively. In multivariable models the odds of death due to drug overdose in neighborhoods in the top decile of income inequality compared to the most equitable neighborhoods decreased from 1.63 to 1.12 when adjusting for the three potential mediators. Path analyses show that the association between income inequality and the rate of drug overdose mortality was primarily explained by an indirect effect through the level of environmental disorder and the quality of the built environment in a neighborhood. Implications of these findings for the reduction of drug overdose mortality associated with the distribution of income are discussed.