Pre-existing chronic physical morbidity and excess mortality in people with schizophrenia: a population-based cohort study

Purpose Schizophrenia is associated with increased premature mortality and physical morbidity. This study aimed to examine prevalence of pre-existing chronic physical diseases, and association between physical multimorbidity burden and mortality rates among patients with newly diagnosed schizophrenia. Methods This population-based cohort study investigated patients with first-recorded diagnosis of schizophrenia between January 2006 and December 2016, using territory-wide medical-record database of public healthcare service in Hong Kong. Physical morbidities were measured by Charlson Comorbidity Index (CCI), taking into consideration both number and severity of physical diseases, and were grouped into nine broad disease categories for analyses. Physical multimorbidity burden was stratified into three levels according to CCI of 0, 1 or ≥ 2. Cox proportional hazards regression models were used to examine associations of physical multimorbidity with mortality rates. Results Of the 13,945 patients, 8.6% ( n = 1207) had pre-existing physical morbidity. Patients with physical morbidity exhibited elevated all-cause mortality rate relative to those without physical morbidity [adjusted HR 2.38 (95% CI 2.04–2.77)]. Gastrointestinal/liver diseases, diabetes and cardiovascular diseases constituted the three most frequently diagnosed physical morbidities, whereas cancers displayed the highest all-cause mortality rate. An increase in physical multimorbidity burden was associated with increased all-cause mortality rate [CCI = 1: 1.98 (1.64–2.40); CCI ≥ 2: 3.08 (2.51–3.77), CCI = 0 as reference]. Conclusion Schizophrenia patients with pre-existing physical morbidity had two-fold increased risk of premature mortality compared to those without physical morbidity. Physical multimorbidity confers incremental impact on excess mortality. Early detection and intervention of physical morbidity in the initial phase of schizophrenia is necessary to reduce avoidable mortality.