Medical comorbidity in women and men with schizophrenia: a population-based controlled study

BACKGROUND: Persons with persistent mental illness are at risk for failure to receive medical services. In order to deliver appropriate preventive and primary care for this population, it is important to determine which chronic medical conditions are most common. OBJECTIVE: We examined chronic medical comorbidity in persons with schizophrenia using validated methodologies. DESIGN: Retrospective analysis of longitudinal administrative claims data from Wellmark Blue Cross/Blue Shield of Iowa. PARTICIPANTS: Subjects with schizophrenia or schizoaffective disorder (N=1,074), and controls (N=726,262) who filed at least 1 claim for medical services, 1996 to 2001. MEASUREMENTS: Case subjects had schizophrenia as the most clinically predominant psychotic disorder, based on psychiatric hospitalization, psychiatrist diagnoses, and outpatient care. Controls had no claims for any psychiatric comorbidity. Using a modified version of the Elixhauser Comorbidity Index, inpatient and outpatient claims were used to determine the prevalence of 46 common medical conditions. Odds ratios (ORs) were adjusted for age, gender, residence, and nonmental health care utilization using logistic regression. RESULTS: Subjects with schizophrenia were significantly more likely to have 1 or more chronic conditions compared with controls. Adjusted OR (95% confidence interval [CI]) were 2.62 (2.09 to 3.28) for hypothyroidism, 1.88 (1.51 to 2.32) for chronic obstructive pulmonary disease, 2.11 (1.36 to 3.28) for diabetes with complications, 7.54 (3.55 to 15.99) for hepatitis C, 4.21 (3.25 to 5.44) for fluid/electrolyte disorders, and 2.77 (2.23 to 3.44) for nicotine abuse/dependence. CONCLUSIONS: Schizophrenia is associated with substantial chronic medical burden. Familiarity with conditions affecting persons with schizophrenia may assist programs aimed at providing medical care for the mentally ill.