The health of populations - individuals, their families and communities - is determined by the complex interaction of many factors - social, political, economic, legal, cultural, historical and biomedical. Of these determinants of health, income has long been recognized as one of the most important. People with higher incomes and higher socio-economic statuses tend to live longer, have lower rates of illness and injury, and are more likely to report that they have good or excellent health. People living in poverty have a lower life expectancy and higher rates of illness across a wide spectrum of diseases. Poor health predisposes individuals and families to homelessness and homelessness exposes individuals and families to particular health problems

Homeless people live in conditions that adversely affect their overall short- and long-term health and contribute to an increased mortality rate. Although deaths among the homeless are occasionally due to freezing, they are mainly the result of injury, and the rigors of street life. Climatic conditions, psychological strain and exposure to communicable disease create and lead to a range of chronic and acute health problems, including injury from cold, tuberculosis, skin diseases, cardio-respiratory disease, nutritional deficiencies, sleep deprivation, musculoskeletal pain and dental trouble. 

Being homeless makes it difficult, and in some cases impossible, to access general health care services. The homeless are unable to: obtain medical treatment without a health card (applicants requires an address); pay for items not covered by provincial medical or drug insurance plans; receive adequate treatment in cases where their personal appearance alarms health providers; make a health appointment (lack of an address and telephone); and receive coordinated care when comprehensive medical records are not kept in one location with one provider. 

Following treatment or hospitalization, a homeless person experiences problems with acquiring adequate follow-up healthcare. The homeless have no place to recuperate and no consistent caregiver. As a result, health care delivery to homeless individuals is concentrated in emergency departments, in the core of large urban centers and in the institutions set up to address their lack of shelter and social supports. There is a need to respond to the acute and chronic health problems of this population and to redirect attention to preventive health. 

Whether as a cause or a consequence of ill health, homelessness has emerged as a fundamental health issue for Canadians. Homelessness affects a significant number of Canadians of allages and is associated with a high burden of illness, yet thehealth care system may not adequately meet the needs of homeless people. The main barriers to good health, among the homeless, include a lack of adequate, safe, accessible and affordable housing that is linked to employability, community support, personal health care and access to health services.