Original article Type-2 diabetes mellitus in schizophrenia: Increased prevalence and major risk factor of excess mortality in a naturalistic 7-year follow-up D. Schoepf a , R. Potluri b , H. Uppal c , A. Natalwala d , P. Narendran e , R. Heun f, * a Department of Psychiatry and Psychotherapy, University of Bonn, 53125 Bonn, Germany b Faculty of Medicine, Imperial College, London SW7 2AZ, United Kingdom c University of Birmingham, Vincent Drive, Edgbaston Birmingham B15 2TT, United Kingdom d Southampton General Hospital, Tremona Road, Southampton, Hampshire SO16 6YD, United Kingdom e Division of Medical Sciences, University of Birmingham, Vincent Drive, Edgbaston Birmingham B15 2TT, United Kingdom f Department of Psychiatry, Royal Derby Hospital, Uttoxeter Road, Derby DE22 3WQ, United Kingdom 1. Introduction Type 2 diabetes mellitus (T2DM) is a metabolic disease that results from an interaction between genetic predispositions and environmental factors [24,35]. The overall prevalence of detected diabetes mellitus in the general population in industrialised countries is around 3–4%. T2DM accounts for 85–90% of all diabetic cases [27]. The World Health Organisation has predicted that by 2030 the number of adults with diabetes will almost double worldwide, largely as a result of an ageing population and of increasing obesity following changes in human activity and nutrition [60]. The pathogenesis of T2DM is characterized by a combination of impaired insulin activity through insulin resis- tance, and relative insulin deficiency through a dysfunction of the pancreatic b-cell [59]. An important stage in the progression from normal insulin physiology to T2DM is pre-diabetes. Individuals with impaired fasting glucose and/or impaired glucose tolerance are classified to have pre-T2DM [5]. Heterogeneity of T2DM is expressed by an overlap of T2DM with obesity and the metabolic syndrome. This varies in different phases of life, in different cultures and populations [22]. Etiology is not yet sufficiently clear. Recognized risk factors include advancing age, weight gain, altered European Psychiatry 27 (2012) 33–42 A R T I C L E I N F O Article history: Received 27 October 2009 Received in revised form 25 December 2010 Accepted 5 February 2011 Available online 13 May 2011 Keywords: Schizophrenia Diabetes mellitus Co-morbidity Epidemiology Mortality A B S T R A C T Objective: Physical co-morbidity including type 2 diabetes mellitus is more prevalent in patients with schizophrenia compared to the general population. However, there is little consistent evidence that co- morbidity with diabetes mellitus and/or other diseases leads to excess mortality in schizophrenia. Thus, we investigated whether co-morbidity with diabetes and other somatic diseases is increased in schizophrenics, and if these are equally or more relevant predictors of mortality in schizophrenia than in age- and gender-matched hospitalised controls. Methods: During 2000–2007, 679 patients with schizophrenia were admitted to University Hospital Birmingham NHS Trust. Co-morbidities were compared with 88,778 age- and gender group-matched hospital controls. Predictors of mortality were identified using forward Cox regression models. Results: The prevalence of type 2 diabetes mellitus was increased in schizophrenia compared to hospitalised controls (11.3% versus 6.3%). The initial prevalence of type 2 diabetes mellitus was significantly higher in the 100 later deceased schizophrenic patients (24.0%) than in those 579 surviving over 7 years (9.2%). Predictors of mortality in schizophrenia were found to be age (relative risk [RR] = 1.1/ year), type 2 diabetes mellitus (RR = 2.2), pneumonia (RR = 2.7), heart failure (RR = 2.9) and chronic renal failure (RR = 3.2). The impact of diabetes mellitus on mortality was significantly higher in schizophrenia than in hospital controls (RR = 2.2 versus RR = 1.1). In agreement, deceased schizophrenics had significantly suffered more diabetes mellitus than deceased controls (24.0 versus 10.5%). The relative risks of mortality for other disorders and their prevalence in later deceased subjects did not significantly differ between schizophrenia and controls. Conclusion: Schizophrenics have more and additionally suffer more from diabetes: co-morbidity with diabetes mellitus is increased in schizophrenia in comparison with hospital controls; type 2 diabetes mellitus causes significant excess mortality in schizophrenia. Thus, monitoring for and prevention of type 2 diabetes mellitus is of utmost relevance in hospitalised patients with schizophrenia. ß 2011 Elsevier Masson SAS. All rights reserved. * Corresponding author. Tel.: +44 1332 623 877. E-mail address: heun@gmx.com (R. Heun). 0924-9338/$ – see front matter ß 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.eurpsy.2011.02.009