摘要：Objectives. We quantified tobacco-, alcohol-, and drug-attributable deaths and their contribution to mortality disparities among homeless adults. Methods. We ascertained causes of death among 28 033 adults seen at the Boston Health Care for the Homeless Program in 2003 to 2008. We calculated population-attributable fractions to estimate the proportion of deaths attributable to tobacco, alcohol, or drug use. We compared attributable mortality rates with those for Massachusetts adults using rate ratios and differences. Results. Of 1302 deaths, 236 were tobacco-attributable, 215 were alcohol-attributable, and 286 were drug-attributable. Fifty-two percent of deaths were attributable to any of these substances. In comparison with Massachusetts adults, tobacco-attributable mortality rates were 3 to 5 times higher, alcohol-attributable mortality rates were 6 to 10 times higher, and drug-attributable mortality rates were 8 to 17 times higher. Disparities in substance-attributable deaths accounted for 57% of the all-cause mortality gap between the homeless cohort and Massachusetts adults. Conclusions. In this clinic-based cohort of homeless adults, over half of all deaths were substance-attributable, but this did not fully explain the mortality disparity with the general population. Interventions should address both addiction and non-addiction sources of excess mortality. Over 2 million people experience homelessness annually in the United States. 1 US-based studies of homeless adults have found varied but generally high rates of substance use, including a 68% to 80% prevalence of cigarette smoking, 2–6 a 29% to 63% lifetime prevalence of alcohol use disorders, 7–13 and a 20% to 59% lifetime prevalence of drug use disorders. 7–13 Mortality rates among homeless individuals exceed those in non-homeless people by a considerable margin, 14–26 but the extent to which substance use contributes to this disparity is uncertain. In a prior study of homeless adults in Boston, Massachusetts, we found the rate of deaths caused by drug overdose to be approximately 20 times higher than the rate in the general population. 14 Similar findings have been documented in New York City, New York, and San Francisco, California. 27,28 Overdose deaths draw attention to the overt complications of drug use among homeless people but represent only a single dimension of substance-attributable mortality. Tobacco, alcohol, and drug use may contribute to other common causes of death among homeless people, such as cancer, heart disease, liver cirrhosis, and HIV. 14–17 The population attributable fraction (PAF) represents the proportion of these deaths that would not have occurred in the absence of tobacco, alcohol, or drug use. 29,30 PAF methods form the basis of studies conducted by the US Centers for Disease Control and Prevention (CDC) 31,32 and the Global Burden of Disease investigators 33 to quantify the impact of substance use and other risk behaviors on health outcomes. In this study, we describe a novel application of PAF-based methods to estimate tobacco-, alcohol-, and drug-attributable mortality rates among 28 033 adults who used Boston Health Care for the Homeless Program (BHCHP) services from 2003 to 2008. We compared our findings with the Massachusetts general population to examine the degree to which mortality disparities between these groups are driven by substance-attributable deaths. Quantifying the burden of tobacco-, alcohol-, and drug-attributable deaths among homeless individuals has the potential to inform upstream efforts at disease prevention and guide clinical priority setting around the delivery of addiction services for this group of people. Additionally, understanding the extent to which these deaths contribute to the mortality gradient between homeless adults and the general population may provide insight about the ways to reduce this disparity.
