Long term outcomes after COVID-19 in patients with schizophrenia: a historical cohort study in a health maintenance organization.

Background: Severe mental illness may affect health behaviors and outcomes during pandemics. Few studies have assessed whether people living with schizophrenia spectrum disorders (SSD) experienced adverse COVID-19 outcomes.

Methods: In a population-based historical cohort study comprising members of a health maintenance organization, we included 1273 patients with SSD and 12,730 age- and sex-matched controls tested for SARS-CoV-2 between March 2020 and May 2022. We assessed the association between schizophrenia and hospitalization, hospital length-of-stay, 30-day, and one-year mortality, constructing multiple linear regression and logistic regression models adjusting for sociodemographic factors, BMI, smoking, number of comorbidities, and vaccinations. We also assessed whether vaccination modified the association between schizophrenia and mortality.

Results: Among patients with SSD, 477 (37.5%) had a positive test, compared to 6203 (48.7%) in the comparison group. patients with SSD were at increased risk of hospitalization (adjusted odds ratio (OR_adj) 3.44, 95% confidence interval (CI): 2.88-4.11, p < 0.001); longer length-of-stay (β = 1.20, p < 0.001); increased 30-day (OR_adj 9.07, 95%CI 3.11-26.44); and one-year mortality (OR_adj 6.27, 95%CI: 2.73-14.39). Further adjustment for vaccination altered the OR for 30-day mortality (OR_adj 4.54, 95%CI: 1.54-13.38). Additionally, the association between schizophrenia and 30-day mortality was attenuated in strata of vaccinated (OR 4.79, 95%CI: 0.82-28.13, p = 0.082), vs. unvaccinated individuals (OR 7.53, 95%CI 2.19-25.92, p = 0.001), respectively.

Conclusions: In our cohort, patients with SSD experienced a significantly higher rate of hospitalization, length of stay, and mortality following a positive SARS-CoV-2 test, even after adjusting for important prognostic factors. COVID-19 vaccination modified these risks.