Health conditions and referral patterns among people experiencing homelessness: a 10-Year longitudinal study of specialized primary care in Hamburg, Germany

Background Homelessness has increased substantially across Europe in recent years and is associated with a high burden of disease and premature mortality. However, longitudinal evidence on the spectrum of health conditions and healthcare referral patterns among people experiencing homelessness remains limited. This study aimed to describe the most common diagnoses in this population and examine their associations with referral to specialist outpatient care and referral to hospital. Methods We conducted a retrospective longitudinal study using routinely collected clinical data from three specialized primary care centers for people experiencing homelessness in Hamburg, Germany. Data from 5,055 patients attending 13,330 consultations between June 5, 2013, and March 28, 2024, were analyzed. Diagnoses were coded by healthcare professionals according to ICD-10 criteria. The primary outcomes were referral to specialist outpatient care and referral to hospital. Associations between diagnoses and referral outcomes were assessed using regression analyses and are presented as odds ratios (ORs) with 95% confidence intervals (CIs). Results The mean age of patients was 44.6 years (SD, 13.2), and 4,207 (83.2%) were male. Mental and behavioral disorders were the most frequently recorded diagnoses (1,436 patients, 28.4%), particularly disorders related to psychoactive substance use (817, 16.2%) and alcohol use (592, 11.7%). Overall, 10.9% of consultations resulted in referral, including 5.5% to specialist outpatient care and 5.4% with referral to hospital. Alcohol-related disorders (OR, 1.76; 95% CI, 1.39–2.23) and injuries and poisoning, including drug intoxication (OR, 1.64; 95% CI, 1.31–2.05), were significantly associated with referral to hospital. Referral to specialist outpatient care was more likely among older patients (OR per 10-year increase, 1.34; 95% CI, 1.22–1.47) and those presenting with musculoskeletal conditions. Most consultations (89.1%) did not result in a documented referral. Conclusions Specialized primary care services were able to address the majority of health problems among people experiencing homelessness, with referral required in only a minority of consultations. Strengthening and integrating such services may improve access to care and support continuity of treatment across healthcare settings. Further research should evaluate interventions targeting mental health and substance use disorders, which represented the most common health concerns. Alcohol-related disorders were also associated with increased referral to hospital. Trial registration Not applicable.