Risk factors for unplanned hospital admission in a specialist homeless general practice population: case-control study to investigate the relationship with tri-morbidity.

Background: 'Tri-morbidity' describes the complex comorbidity of chronic physical illness, mental illness, and alcohol and/or drug misuse within the homeless population. Poor health outcomes of homeless people are reflected by the higher rate of unplanned hospital admissions compared with the non-homeless population.

Aim: To identify whether tri-morbidity is a risk factor for unplanned hospital admissions in the homeless population.

Design And Setting: A case-control study of patients who were registered with a specialist homeless GP surgery in Brighton (72 cases and 72 controls).

Method: Cases were defined as those who had ≥1 overnight hospital admission within a 12-month period. Controls were matched for demographics but with no hospital admission. The primary care record was analysed, and tri-morbidity entered into binomial logistic regression with admission as the dichotomous dependent variable.

Results: The logistic regression analysis demonstrated that other enduring mental health disorders and/or personality disorder (odds ratio [OR] 3.84, 95% confidence interval [CI] = 1.56 to 9.44), alcohol use (OR 2.92, 95% CI = 1.42 to 5.98), and gastrointestinal disorder (OR 2.90, 95% CI = 1.06 to 7.98) were independent risk factors for admission. Tri-morbidity increased odds of admission by more than four-fold (OR 4.19, 95% CI = 1.90 to 9.27).

Conclusion: This study shows that tri-morbidity is an important risk factor for unplanned hospital admissions among the homeless population, and provides an interesting starting point for the development of a risk stratification tool to identify those at risk of unplanned admission in this population.