Association between prior somatic disease and 5-year relapse risk among 11,856 incident patients with schizophrenia

Somatic diseases have been associated with an increased risk for subsequent schizophrenia; however, it is unknown whether prior somatic diseases negatively affect early treatment outcomes after a first-time schizophrenia diagnosis.

We included all individuals born in Denmark after January 1^st, 1977 and first-time diagnosed with schizophrenia between January 1^st, 1996 and December 31^st, 2015. We identified all life-time somatic hospital contacts and all prescriptions within the year before the first-time schizophrenia diagnosis and followed patients for up to five years regarding risk for schizophrenia (re)-hospitalization (relapse). We performed Cox regression analyses calculating hazard rate ratios (HRR) including 95%-confidence intervals (CI) and adjusted for relevant confounders.

We followed a total of 11,856 patients with a first-time schizophrenia diagnosis (58.7% male, mean age 23.1 (SD = 4.7) years) for 39,033 person-years, whereof 5506 (46.4%) had relapse with schizophrenia re-hospitalization during 5-year of follow-up. Somatic hospital contacts ever before (95.4%; HRR = 1.30; 95%-CI = 1.07-1.59), and specifically during the year before schizophrenia diagnosis (42.5%; HRR = 1.36; 95%-CI = 1.11-1.66) were associated with an increased risk of schizophrenia relapse as were a greater number of prior somatic hospital contacts (p < 0.001). Individuals with up to four different prescriptions for somatic medications showed a trend towards a slightly lower risk of relapse.

Somatic diseases and health seeking patterns might have an impact on the course of schizophrenia, where severe somatic comorbidity, specifically during the year before first-time schizophrenia diagnosis, seem to negatively affect early treatment course, whereas previous somatic medication use may indicate a better compliance and help-seeking behavior.