In a large, long-term study, homeless men and women died at rates that were respectively 5.6 and 6.7 times that of the general Danish population, according to Sandra Nielsen, BSc, of Mental Health Centre Copenhagen, and colleagues.
The researchers also confirmed high rates of psychiatric disorders among the homeless population, but surprisingly psychiatric disorders alone did not seem to increase mortality, Nielsen and colleagues reported online in The Lancet.
The homeless are a transient group and difficult to study, the researchers noted. But in Denmark local governments are required to provide shelter for a small fee to anyone who needs it.
The homeless shelters record a client's Civil Registration Number, which is also linked to databases containing vital statistics such as psychiatric admissions, outpatient care, and causes of death, they noted.
Taken together, the data allowed the researchers to analyze demographics and outcomes for a cohort of 32,711 people (23,040 men and 9,671 women) who stayed at least one night in a homeless shelter between 1999 and 2009.
They found that:
- Most had registered psychiatric disorders (58.2% or 14,381 men; 62.4% or 5,632 women).
- Substance abuse diagnosis was the most frequent diagnosis among men and women (49% or 11,286 men; 36.9% or 3,564 women).
- During the study period, 16.7% or 3,839 men and 9.8% or 951 women died.
- The standardized mortality ratio, compared with the general population, was 5.6 for men and 6.7 for women.
- External causes, including suicide and violence, accounted for 27.9% of the 4,161 deaths for which information on the cause was available.
The increased mortality rate was also expressed as a loss of life expectancy. Men who became homeless between the ages of 15 and 24 could expect to live another 38.7 years, compared with 60.3 years for the general Danish population, the researchers found.
The corresponding figures for women of that age group were 47.4 years for the homeless and 64.8 years for the general population, they reported.
A multivariable analysis showed that the risk of death was not significantly different among homeless people who had no psychiatric contact; people who had been diagnosed with schizophrenia spectrum disorder; or people who had some other psychiatric disorder.
On the other hand, Nielsen and colleagues found, having a substance abuse diagnosis, or being addicted and schizophrenic, significantly increased the risk of death. Specifically:
- The hazard ratios (HR) for death for men with substance abuse disorder or dual diagnoses were both 1.6, with 95% confidence intervals from 1.5 to 1.7 and 1.4 to 1.7, respectively.
- The HR for death for women with substance abuse disorder or dual diagnoses were 2.6 and 2.9, respectively, with 95% confidence intervals from 2.1 to 3.1 and 2.3 to 3.6, respectively.
For men and women, the risk of death rose with the number of times they used homeless shelters, the researchers reported.
The study's strengths include its large numbers and complete data on psychiatric hospital contacts and deaths, the authors noted. But Nielsen and colleagues cautioned that the study did not include homeless people who avoided shelters.
As well, they cautioned, the study population included all people who spent any time in a shelter, and some may have been only temporarily homeless.
Nielsen and colleagues also noted that the study cannot justify any causal statements relating homelessness and psychiatric disorders, although as a matter of public policy it might be best to tackle both issues at once.
The study demonstrates that "homeless people are at one extreme end of the spectrum of health inequalities," argued John Geddes, MD, and Seena Fazel, MD, both of the University of Oxford in Oxford, England
In an accompanying commentary, they noted that the mortality rates found by the Danish researchers might actually be conservative because homeless people who did not go to shelters were excluded.
The latter are "harder to study, and might have still higher rates of substance misuse and hence mortality," Geddes and Fazel noted.
One implication of the study, they argued is that "integrated psychiatric and substance abuse treatment is necessary to address inequalities."
The study was supported by the Danish Council for Independent Research. The authors said they had no conflicts.
The commentary authors said they had no conflicts.
- Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
The LancetSource Reference: Nielsen SF, et al "Psychiatric disorders and mortality among people in homeless shelters in Denmark: a nationwide register-based cohort study" Lancet 2011; DOI: 10.1016/S0140-6736(11)60747-2.
The LancetSource Reference: JGeddes JR, Fazel S "Extreme health inequalities: Mortality in homeless people" Lancet 2011; DOI: 10.1016/S0140-6736(11)60885-4.