Abstract
BACKGROUND: Homelessness might increase the risk of premature mortality, but evidence is scarce, imprecise, and is mostly limited to rough sleepers as opposed to more common types of homelessness. METHODS: Published studies were retrieved through a systematic search of MEDLINE, Embase PsycINFO and Scopus from inception to December 2024. Unpublished data were identified from open-access data archives. We used random-effects meta-analysis to combine effect estimates from published and unpublished data. This review is registered at PROSPERO (CRD42023430984). FINDINGS: We included 116 studies from Europe, the USA, South America, Africa, Asia, and Australia. The meta-analysis of all-cause mortality comprised 110,892,271 people (1,618,049 exposed to homelessness). The risk of all-cause mortality was significantly increased in people exposed to homelessness (Relative risk [RR] 2·12 [95% CI 1·91-2·57], p<0·001, I(2)=99·7%), with risks similar in men (3·88, 2·69-5·06) and women (3·46, 2·17-4·70). This risk was most elevated in people who had slept rough (7·63, 3·29-11·97), followed by those who used low-cost hotels (5·18, 1·14-9·23), then hostels (3·44, 2·10-4·77). In analyses of cause-specific mortality (26,291,900 people, 1,202,205 homeless), summary RR estimates were elevated for 33 of the 36 (92%) causes of death and highest for deaths due to psychoactive substance use disorder (21·36, 14·44-31·67), accidental injuries (13·15, 5·46-31·69), drug-overdose (10·80, 6·37-18·31), and those that are alcohol-related (5·93, 1·10-22·04). No evidence of publication bias was detected. INTERPRETATION: Homeless people experience an increased risk of premature mortality across an array of health outcomes. That the most extreme inequities have an interrelated aetiology suggests a cross-sectoral medical, housing, and social care response is required. FUNDING: The Centre for Homelessness Impact, Health and Care Research Wales, UK Medical Research Council (MR/P023444/1) and the US National Institute on Aging.