Clinical Epidemiology (Sep 2016)
Association between Global Assessment of Functioning scores and indicators of functioning, severity, and prognosis in first-time schizophrenia
Abstract
Ole Köhler,1 Henriette Thisted Horsdal,2 Lone Baandrup,3,4 Ole Mors,1,5 Christiane Gasse2 1Psychosis Research Unit, Aarhus University Hospital, Risskov, 2National Centre for Register‑based Research, Department of Economics and Business Economics, Aarhus University, Aarhus, 3Center for Neuropsychiatric Schizophrenia Research, Mental Health Center Glostrup, 4Mental Health Center Copenhagen, Copenhagen, 5iPSYCH, The Lundbeck Foundation Initiative for Integrative Psychiatric Research, Aarhus University, Aarhus, Denmark Background: Assessment of psychosocial functioning in people with schizophrenia is important. The Global Assessment of Functioning (GAF-F) scale represents a widely applied, easy, and quick tool, but its validity and reliability have been debated. The aim was to investigate whether GAF-F scores are associated with other indicators of functioning, severity, and hospitalization.Methods: A Danish population-based cohort study of adults (≥18 years) with a recorded GAF-F score at first-time schizophrenia diagnosis during 2004–2011 was performed. The internal validity of GAF-F was evaluated by assessing its association with other baseline measures of functioning and illness severity. Risk of schizophrenia hospitalization within 2 years was evaluated using Cox regression stratified by sex and adjusted for age, year of diagnosis, and inpatient/outpatient status at diagnosis.Results: We identified 2,837 cases of schizophrenia with a GAF-F score at first-time diagnosis (73.0% inpatients; 62.6% males). GAF-F was associated with several baseline measures of functioning and illness severity, such as female sex, being in work, and a longer baseline hospitalization. Lower GAF-F scores were associated with higher hospitalization risk among males (reference GAF-F 61–100): GAF-F 51–60: hazard rate ratio (HRR) =1.24 (95% confidence interval [CI] =0.89–1.75); GAF-F 41–50: HRR =1.31 (95% CI =0.97–1.77); GAF-F 31–40: HRR =1.36 (95% CI =1.01–1.82); GAF-F 21–30: HRR =1.50 (95% CI =1.09–2.06); and GAF-F 1–20: HRR =2.30 (95% CI =1.36–3.90), fitting a dose–response relationship (P=0.031). This association was not found in females.Conclusion: GAF-F at first-time schizophrenia diagnosis showed good internal validity against other measures of functionality in a Danish hospital setting. Severe impairment (as measured by the GAF-F score) at first-time schizophrenia diagnosis was associated with a higher risk of 2-year hospitalization among males, which may indicate sex differences in the course of disease and treatment response. Keywords: Global Assessment of Functioning, GAF, schizophrenia, hospitalization, incident schizophrenia, early phase treatment
