Physical comorbidity and its relevance on mortality in schizophrenia: a naturalistic 12-year follow-up in general hospital admissions

Abstract

Schizophrenia is a major psychotic disorder with significant comorbidity and mortality. Patients with schizophrenia are said to suffer more type-2 diabetes mellitus (T2DM) and diabetogenic complications. However, there is little consistent evidence that comorbidity with physical diseases leads to excess mortality in schizophrenic patients. Consequently, we investigated whether the burden of physical comorbidity and its relevance on hospital mortality differed between patients with and without schizophrenia in a 12-year follow-up in general hospital admissions. During 1 January 2000 and 31 June 2012, 1418 adult patients with schizophrenia were admitted to three General Manchester NHS Hospitals. All comorbid diseases with a prevalemce ≥1% were compared with those of 14,180 age- and gender-matched hospital controls. Risk factors, i.e. comorbid diseases that were predictors for general hospital mortality were identified using multivariate logistic regression analyses. Compared with controls, schizophrenic patients had a higher proportion of emergency admissions (69.8 vs. 43.0%), an extended average length of stay at index hospitalization (8.1 vs. 3.4 days), a higher number of hospital admissions (11.5 vs. 6.3), a shorter length of survival (1895 vs. 2161 days), and a nearly twofold increased mortality rate (18.0 vs. 9.7%). Schizophrenic patients suffered more depression, T2DM, alcohol abuse, asthma, COPD, and twenty-three more diseases, many of them diabetic-related complications or other environmentally influenced conditions. In contrast, hypertension, cataract, angina, and hyperlipidaemia were less prevalent in the schizophrenia population compared to the control population. In deceased schizophrenic patients, T2DM was the most frequently recorded comorbidity, contributing to 31.4% of hospital deaths (only 14.4% of schizophrenic patients with comorbid T2DM survived the study period). Further predictors of general hospital mortality in schizophrenia were found to be alcoholic liver disease (OR = 10.3), parkinsonism (OR = 5.0), T1DM (OR = 3.8), non-specific renal failure (OR = 3.5), ischaemic stroke (OR = 3.3), pneumonia (OR = 3.0), iron-deficiency anaemia (OR = 2.8), COPD (OR = 2.8), and bronchitis (OR = 2.6). There were no significant differences in their impact on hospital mortality compared to control subjects with the same diseases except parkinsonism which was associated with higher mortality in the schizophrenia population compared with the control population. The prevalence of parkinsonism was significantly elevated in the 255 deceased schizophrenic patients (5.5 %) than in those 1,163 surviving the study period (0.8 %, OR = 5.0) and deceased schizophrenic patients had significantly more suffered extrapyramidal symptoms than deceased control subjects (5.5 vs. 1.5 %). Therefore patients with schizophrenia have a higher burden of physical comorbidity that is associated with a worse outcome in a 12-year follow-up of mortality in general hospitals compared with hospital controls. However, schizophrenic patients die of the same physical diseases as their peers without schizophrenia. The most relevant physical risk factors of general hospital mortality are T2DM, COPD and infectious respiratory complications, iron-deficiency anaemia, T1DM, unspecific renal failure, ischaemic stroke, and alcoholic liver disease. Additionally, parkinsonism is a major risk factor for general hospital mortality in schizophrenia. Thus, optimal monitoring and management of acute T2DM and COPD with its infectious respiratory complications, as well as the accurate detection and management of iron-deficiency anaemia, of diabetic-related long-term micro- and macrovascular complications, of alcoholic liver disease, and of extrapyramidal symptoms are of utmost relevance in schizophrenia.