Characterising infectious disease mortality in severe mental illness: A retrospective matched cohort study

Summary Background Evidence suggests that people with severe mental illness (SMI) are at an increased risk of infection mortality compared to the general population. Little is known about how this risk might differ across infection types, and the potential impact of sociodemographic and clinical factors. We investigated associations between SMI and infection mortality in a population-based cohort, examining variation by infection type and potential moderating factors. Study design This retrospective matched cohort study used national primary care data from the Clinical Practice Research Datalink (CPRD) from 1 January 2000 to 31 December 2019 linked with Office of National Statistics (ONS) mortality data. Competing risks regression and cause-specific hazard models assessed risk of infection mortality in people with SMI versus non-SMI controls. We examined risk across different infection types and assessed the impact of sociodemographic and clinical factors. Study results Our cohort comprised 84,494 people with SMI matched on age, gender, and GP practice with 84,494 non-SMI controls. Fully adjusted models showed that people with SMI were more likely to die from any infection compared to non-SMI controls (adjusted hazards ratio (aHR)=1.58, 95% confidence intervals (CI)=1.44 to 1.74). Infection-specific analyses revealed increased risk of death from respiratory (aHR=1.69, 95% CI=1.51 to 1.89), gastrointestinal (aHR=2.01, 95% CI=1.16 to 3.48), and renal/urinary (aHR=1.70, 95% CI=1.32 to 2.19) infections in the SMI group. Conclusions People with SMI are at increased risk of infection mortality, especially from respiratory, gastrointestinal, and renal/urinary infections. We recommend prioritising this group for preventative measures including influenza and pneumococcal vaccines.