Mortality in a Cohort of Street Youth in Montreal FREE

The characteristics of street youth vary depending on the social environment where they live. In Canada and the United States, street youth are generally 25 years or younger, and approximately a third of them are girls. They are homeless or, more frequently, they live in highly unstable residential conditions. Different subcultures are represented among them, including punks, rappers, skinheads, and others.^1- 2 Despite some heterogeneity, these youth share many characteristics that jeopardize their development and health; they are highly entrenched in the streets and frequently engage in high-risk behaviors such as prostitution³ and substance abuse, including injection drug use.^4- 10 They are increasingly recognized as a population at risk for a wide range of physical and mental health problems. Many studies have examined their precarious living conditions and risky sexual and substance use behaviors and the impact of these factors on their health. These studies have brought to light their extreme vulnerability in terms of sexually transmitted diseases, human immunodeficiency virus (HIV) infection, viral hepatitis, drug dependence, and mental health problems.^{6- 7,9,11- 18} Other studies have looked at the sexual abuse and physical violence that street youth endure.^19- 24 Data on the ultimate consequence of these problems, the death of street youth, are sparse.

Several studies have addressed mortality among homeless individuals.^25- 33 Of these, only 5 presented data for youth younger than either 25 or 30 years. A study of residents in New York City homeless shelters showed a mortality ratio of 2.7 for men 20 to 24 years of age.³³ In Toronto, Ontario, a ratio of 8.3 was measured among men 18 to 24 years old using homeless shelters.²⁷ In Boston, Mass, the mortality ratio for males 18 to 24 years old having been in contact with the Boston Health Care for the Homeless Program was 5.9; among females in the same age category, this ratio was 11.8.²⁹ In Copenhagen, Denmark, a mortality ratio of 28.5 was observed among female users of hostels for homeless people who were 15 to 24 years of age; for male users of that age group, the mortality ratio was 13.3.²⁵ Finally, a mortality ratio of 37.3 was calculated for male rough sleepers (individuals with no fixed address) in London who were 16 to 29 years of age.³² All these studies clearly showed that homeless youth experienced mortality rates much higher than their counterparts in the general population, although the ratio varied greatly from one study site to another.

Two of the reviewed studies presented causes of death by age group. In Boston, the principal cause of death among males 18 to 24 years old was homicide, followed by "poisoning and injuries other than motor vehicle accident." Among females, also 18 to 24 years old, the 2 main causes of death, of equal importance, were homicide and motor vehicle accident.²⁹ The leading identified cause of death among Toronto male shelter users 18 to 24 years of age was accident (other than being struck by a motor vehicle and poisoning), followed equally by unintentional overdoses and suicide.²⁷

These studies provided valuable information on mortality among young homeless individuals. However, 3 of them were based on data extracted from administrative databases and included little or no data on subjects.^27,29,32 Even though this allowed for the identification of causes of death, it precluded the analysis of factors associated with death. Risk factor data were obtained in 2 studies.^25,33 However, since the design of these studies did not include any follow-up over time, analyses were based only on baseline data. In addition, no analyses restricted to younger participants were reported.

In 1995, we initiated a prospective cohort study to determine the incidence and risk factors for HIV infection among street youth in Montreal, Quebec. In the first months following study inception, several participants died, leading us to add the analysis of mortality to the study objectives.³⁴ Our additional study objectives, in the context of a longitudinal study design, were as follows: (1) to estimate the mortality rate among street youth, (2) to determine the causes of death of these youth, and (3) to identify factors that increase their risk of death.

The complete methodology of the study was described previously.¹⁸ Briefly, criteria for entry in the cohort were as follows: (1) in the last year, having either regularly used the services of community-based street youth agencies or been without a place to sleep more than once; (2) being 14 to 25 years of age; (3) speaking English or French; and (4) being able to provide informed consent and to complete an interviewer-administered questionnaire. The street youth agencies operated drop-in centers, shelters, and outreach vans; the range of services offered included food, short-term housing, social services, and prevention interventions such as hepatitis B vaccination and needle exchange.

Participants were recruited from January 24, 1995, to September 30, 2000. Study interviewers enrolled them through regular visits to all major street youth agencies in Montreal. Participants were interviewed twice a year. Detailed contact information was collected at each interview. Visiting community organizations, leaving messages with friends and family, sending letters, and contacting other organizations (such as Social Security, drug treatment centers, probation offices, prisons, and youth rehabilitation centers) were also used to follow up participants. At each visit, after giving informed consent, they completed a 45-minute questionnaire, covering sociodemographic characteristics, alcohol and drug use, and sexual behaviors, and provided samples of gingival exudate for HIV antibody testing. Each visit was financially compensated (Can $20). Ethical approval was provided by the institutional review board of the Faculty of Medicine, McGill University, Montreal, Quebec.

Participants were eligible for follow-up until they reached 30 years of age or until they reported, in 4 consecutive study questionnaires, not using services from street youth organizations and not being homeless (ie, sleeping outside or in a shelter or staying with friends out of necessity) in Montreal; we thereafter refer to the latter participants as "no longer street-involved."

Vital status of participants was verified throughout the study, whenever we had information that a participant might have died. These ongoing verifications were made with the coroner's office. For each confirmed death, a copy of the coroner's report was obtained. Furthermore, at the end of the study, the vital status of all participants was ascertained with the Institut de la Statistique du Québec for the years 1995 through 2001; permission for access was granted by the Commission d'Accès à l'Information (Quebec's access to information commission).

The primary source of information on causes of death was the coroner's reports. Whenever an autopsy was performed, a summary of the results was available in the coroner's report. For cases not investigated by the coroner (n = 3), we used the coded causes mentioned on the death certificate and provided by the Institut de la Statistique du Québec. These causes were coded using the International Classification of Diseases, Ninth Revision (ICD-9), for deaths occurring in 1995 to 1999, or the International Classification of Diseases, 10th Revision (ICD-10), for those occurring in 2000 and 2001. One participant died outside Canada. We were informed of the death, and of its cause, by the youth's mother.

The follow-up period for every subject started at recruitment and ended at the first of the following events: (1) death, (2) age 30 years, (3) being no longer street-involved, or (4) 6 months after his/her last questionnaire. Mortality rates were calculated overall and by subgroups defined according to various characteristics. These rates were estimated using the person-time method (number of deaths divided by person-years of follow-up); 95% confidence intervals (CIs) were calculated using the Poisson distribution.

Standardized mortality ratios were calculated using the indirect method of standardization by sex and age group; the comparison group was the general population of the province of Quebec for 1996. Ninety-five percent CIs were based on Byar's approximation.³⁵

Predictors of mortality were identified using univariate and multivariate Cox hazard regression analyses. Hazard ratios for potential predictors and the corresponding 95% CIs were determined using univariate Cox regression. All variables with P values ≤.10 in univariate analyses were included in a multivariate Cox model using a backward procedure (with likelihood ratio statistics). Those with P values ≤.05 were retained in the final model. The potential confounding effect of variables excluded by the backward procedure was tested by adding them, one at a time, in the final model. Finally, 2 × 2 interactions between independent predictors were tested.

In the Cox analyses and for estimation of the mortality rates, all independent variables other than sex were treated as time-dependent, either irreversible or transient. Time-dependent irreversible predictors were measured at each interview, but their value could change only once, from absence of the factor to presence of it. These predictors included being older than 18 years, HIV infection (based on the test performed at each questionnaire), homosexual activities (with regular or casual partners), and sexual abuse.

For time-dependent transient predictors, exposure was measured at each interview and their value could vary from questionnaire to questionnaire. Predictors corresponding to the preceding 6 months were homelessness, drug injection, and survival sex (defined as the exchange of sex for money, drugs, or something else). Predictors assessed for the preceding month were daily alcohol use and use of more than 2 categories of drugs (9 categories were considered: marijuana, cocaine/crack, heroin, speedball [cocaine and heroin combined], amphetamines, hallucinogens [mushrooms, LSD (lysergic acid diethylamide), PCP (phencyclidine)], solvents, medications used for nonmedical reasons, and other drugs). Statistical analyses were performed with SPSS for Windows (release 11.0.1).

From January 24, 1995, to September 30, 2000, 1013 youth were recruited in the cohort. Approximately 12% of offers to participate were refused. Participants completed from 1 to 11 questionnaires (average of 5.3 questionnaires per participant; 87.2% completed at least 1 follow-up questionnaire after their recruitment questionnaire). During follow-up, 145 participants reached 30 years of age or were no longer street-involved. Overall, participants cumulated 2822 person-years of follow-up, for an average follow-up of 33.4 months per participant.

At study entry, the mean age of participants was 19.9 years. As indicated in Table 1, two thirds were boys, most were born in Canada, 80% had been homeless in the 6 months prior to study entry, and a quarter had ever been involved in survival sex. Substance use was high among them with the majority of youth having ever used cannabis, hallucinogens, and cocaine or crack at entry. Almost half of the participants had ever injected drugs. Fourteen participants were HIV-infected at study entry, for a prevalence of 1.4%; 16 incident HIV infections were observed during the study period.³⁶

Twenty-six of the 1013 participants died during follow-up. Three additional deaths occurred outside the follow-up period: 1 participant died 30 months after his last interview (he had refused to continue participation) and 2 died 16 months after their last interview (1 had been excluded from the cohort since he was no longer street-involved, and 1 had been lost to follow-up). These 3 deaths were excluded from all subsequent analyses.

Causes of death are listed in Table 2. Suicide and drug overdoses were the 2 leading causes of death. Among male participants, suicide was the main cause of death; among female participants, the main cause of death was drug overdose. Five youth died before reaching 20 years of age: 3 of a drug overdose, 1 of unintentional injury, and 1 of suicide. Of the 13 participants who committed suicide, 9 died by hanging, 2 jumped from a bridge, and 2 jumped or ran in front of a moving vehicle. One cause of death was unidentified. All overdose deaths involved illicit drugs, and none of them were classified as intentional by the coroner.

The 26 deaths observed during follow-up represented a mortality rate of 921 per 100 000 person-years (95% CI, 602-1350). Among male participants, the mortality rate was 1148 (95% CI, 720-1739) and among female participants, 442 (95% CI, 120-1131). The standardized mortality ratio was 11.4 (95% CI, 7.4-16.7); the estimates were 11.1 for males (95% CI, 6.9-16.8) and 13.5 for females (95% CI, 3.6-34.5).

Mortality rates by participant characteristic and results of the univariate and multivariate Cox regression analyses are presented in Table 3. The independent predictors of mortality identified in the final model were HIV infection, daily alcohol use (last month), homelessness (last 6 months), drug injection (last 6 months), and male sex. None of the variables excluded by the backward procedure had a confounding effect, and no interactions were detected between variables retained in the final model.

To our knowledge, this study represents the first prospective cohort study on mortality among street youth. It includes longitudinal follow-up and analyses based on time-dependent factors. The mortality rate of 921 per 100 000 person-years observed in our study participants is extremely high, exceeding 11 times the rate observed among youth in the general population. Similar ratios were reported in young homeless in Toronto and Boston,^27,29 while higher ratios were reported in Denmark and England^25,32 and lower ones in New York City.³³

The 2 main causes of death in our study were suicide and drug overdose. It is plausible that some drug overdoses were in fact suicides. Several studies have shown that overdose is often the method chosen by drug users to commit suicide, and that nonintentional and intentional overdoses cannot always be differentiated.^37- 38 The overlap between suicide and overdose may be especially important for females. Male street youth, as those in the general population, are probably more inclined to choose irreversible means, such as hanging, to kill themselves; these deaths can easily be identified as suicide. However, female street youth, as females in the general population, might tend to choose less violent methods, such as overdoses; therefore, these deaths are less likely to be recognized as suicide.³⁹

The causes of death for males in our study were similar to those observed by Hwang in Toronto; the 3 main causes were the same even though the order differed.²⁷ The picture is, however, very different from what was seen in Boston, where the leading cause of death for both males and females was homicide.²⁹ For females in Boston, motor vehicle accident was another leading cause of death; in our study, no female participants died from such a cause. The difference between our results and those of the Boston study regarding death by homicide is not surprising given that the overall homicide rate is 3.8 times higher in the United States than in Canada.⁴⁰

The leading cause of death among Montreal male street youth is similar to the leading cause in the general population.^41- 42 In 2000, the leading cause of death among male Quebec residents 15 to 19 years old and 20 to 24 years old was suicide (38.2% and 36.2% of all deaths in these groups), followed by motor vehicle accident (32.6% and 29.2%). However, among female Quebec residents in the same age groups, the leading cause of death was motor vehicle accident (45.5% and 31.0%) followed by suicide (15.6% and 29.9%).

Being HIV-infected was the strongest independent predictor of death during follow-up. This association might be due to the fact that HIV infection was a direct cause of death. Four of the deceased participants were HIV-infected, including 1 youth who died from hepatitis A and who was also infected with hepatitis C virus. This death was clearly related to his HIV status. For the 3 other cases, the relationship is less clear: 2 died of a drug overdose and 1 of a noninfectious heart condition.

Another important predictor of death was being recently homeless. Hwang⁴³ noted that the literature is not clear about the strength of the association between homelessness and mortality. Part of the problem resides in the difficulty of assessing exposure to homelessness. Shelter use is often equated with homelessness, which can lead to misclassification because periods of life on the street are then not considered. In our study, both types of episodes were included since homelessness was defined as sleeping outside or in a shelter or staying with friends out of necessity. In addition, treating homelessness as a time-dependent variable resulted in a more valid estimation of the association between homelessness and death. Therefore, we can conclude that the risk of death does increase during episodes of homelessness. Given the importance of suicide as a direct cause of death, it is possible that the causal effect of homelessness on mortality is mediated by other factors such as despair during episodes of homelessness.

Two other independent predictors of mortality among street youth were daily alcohol use and drug injection. The association between substance misuse and death has been reported by several authors.^{25,30- 31,33} This finding is coherent with the causes of death that we observed. Eight of the 26 deaths were due to drug overdose. In addition, at least 1 other death was drug-related (the hepatitis A death), not to mention the cases of suicide and unintentional injury that occurred when the youth were intoxicated (6 of the 8 for whom toxicological analyses were conducted). Substance use, which is very frequent among street youth, without doubt carries a high risk of mortality and is responsible for numerous deaths in this young population.

Another identified predictor of mortality was sex. As found in the general population, male sex is associated with an increased risk of death among street youth. However, other authors found that this survival advantage of females did not necessarily hold among young homeless individuals.²⁸ The question of the difference between street-involved men and women regarding death remains open.

Potential limitations must be taken into account when interpreting our results. First, possible misclassification of exposures is always a concern. In our analysis, we chose to end follow-up for a given participant no later than 6 months after his/her last completed questionnaire. Because of that, we consider that potential misclassification was significantly reduced; participants are less likely to have changed exposure category within 6-month intervals. However, the potential misclassification bias related to self-reported behaviors remains. Some youth may have been reluctant to report behaviors that were less socially acceptable. We tried to reduce this to a minimum by giving repeated assurances of confidentiality. Second, we may have underestimated the mortality rate due to deaths occurring outside the province of Quebec. However, we think that the number of such deaths should be very small. Even though these deaths would not have been detected by official sources, we would generally have been informed of them by close family members or friends when tracing participants for their follow-up interviews, as indeed happened for 1 participant.

Given the large diversity of our recruitment sites, we are confident that our findings are generalizable to the population of street youth using street youth services in Montreal. However, these results may not be applicable to those not accessing services; these youth may be further marginalized and at greater risk of death, or, conversely, represent relatively well-organized youth, and at lower risk. Regarding the generalizability of our results to street youth in other Canadian and US cities, the significant similarities in their situations should make our findings applicable to street youth in most major urban centers in these countries. Nevertheless, they may not be applicable to street youth from developing countries who are facing a totally different social environment.

In conclusion, mortality is high in the street youth population. Treatment of addiction and mental health problems should represent public health priorities to prevent deaths in these young people. Additional studies providing a better understanding of the role of other factors such as HIV infection and homelessness are also needed to support the development of appropriate health and social services for these vulnerable youth.