Prevalence of the metabolic syndrome in patients with schizophrenia treated with antipsychotic medication

Abstract

The presence of the metabolic syndrome is an important risk factor for cardiovascular disease and diabetes. There are limited data on the prevalence of the metabolic syndrome in European patients suffering from schizophrenia.

Methods

All consecutive patients with schizophrenia at our university psychiatric hospital and affiliate services were entered in an extensive prospective metabolic study including an oral glucose tolerance test. The prevalence of the metabolic syndrome was assessed based on the National Cholesterol Education Program criteria (NCEP, Adult Treatment Protocol, ATP-III), adapted ATP-III criteria using a fasting glucose threshold of 100 mg/dl (AHA) and on the recently proposed criteria from the International Diabetes Federation (IDF).

Results

The analysis of 430 patients showed a prevalence of the metabolic syndrome of 28.4% (ATP-III), 32.3% (ATP-III A) and 36% (IDF), respectively. The prevalence of the metabolic syndrome in our sample of patients with schizophrenia is at least twice as high compared to an age-adjusted community sample in Belgium.

Conclusion

The metabolic syndrome is highly prevalent among treated patients with schizophrenia. It represents an important risk for cardiovascular and metabolic disorders. Assessment of the presence and monitoring of the associated risks of the metabolic syndrome should be part of the clinical management of patients treated with antipsychotics.

Introduction

Metabolic abnormalities have consistently been identified as a part of schizophrenic illness (Allison et al., 1999, Homel et al., 2002, Meduna et al., 1942, Raphael, 1921). The interest in this topic has recently been renewed since the introduction of second generation antipsychotics and their possible association with metabolic abnormalities (Allison and Casey, 2001, Jin et al., 2004, Meyer and Koro, 2004). The issue of abnormalities in glucose metabolism, in particular diabetes mellitus (DM), has hereby received most attention (De Nayer et al., 2005, Haupt and Newcomer, 2001, Jin et al., 2002, Jin et al., 2004, Newcomer, 2005, Scheen and De Hert, 2005).

However, other conditions such as cardiovascular morbidity, abnormal lipid metabolism and obesity also have a serious impact on the physical health of patients diagnosed with schizophrenia. The importance of diagnosing and treating these medical conditions needs to be stressed. Not only is the presence of these conditions associated with a excess mortality rate because of elevated cardiovascular risk (Brown, 1997, Brown et al., 2000, Osby et al., 2000a, Osby et al., 2000b), it has also been associated with a lower functional outcome (Lyketsos et al., 2002), a higher prevalence of psychotic and depressive symptoms (Dixon et al., 1999), a worse perceived physical health (Dixon et al., 1999, Meyer et al., 2005) and lower adherence to medication (Robinson et al., 2002, Weiden et al., 2004).

Therefore, researchers have developed a growing interest in the Metabolic Syndrome (MetS), which comprises abnormalities in glucose metabolism, lipid metabolism, obesity and blood pressure. The most commonly used definitions for the Metabolic Syndrome are the Adult Treatment Protocol (ATP-III) of the National Cholesterol Education Program (NCEP) (Expert Panel on Detection and Evaluation of Treatment of High Blood Cholesterol in Adults, 2001), and the adapted ATP-III A proposed by the AHA following the ADA lowering of the threshold for impaired fasting glucose to 100 mg/dl (Expert Committee on the Diagnosis and Classification of Diabetes Mellitus, 2003, Grundy et al., 2004). A more recent definition, by the International Diabetes Federation (IDF, 2005), stressed the importance of waist circumference, using both more stringent and ethnic-/race-specific criteria. Recent research on MetS in the general population has indeed provided evidence for the development of ethnic-/race-specific criteria (Cossrow and Falkner, 2004, Ford et al., 2002, Park et al., 2003, Kraja et al., 2005, Misra et al., 2005, Rakugi and Ogihara, 2005). Until now, it has remained unclear to what extent these differences in the general population are due to genetic factors or cultural factors such as life style or economic factors.

To evaluate the prevalence of MetS in patients diagnosed with schizophrenia and the impact of life style and economic factors within distinct ethnic groups, prospective large sample studies in different countries are needed. Only few studies on the prevalence of MetS among patients diagnosed with schizophrenia are available. The prevalence of MetS in these studies was around 40% (Basu et al., 2004, Heiskanen et al., 2003), but limited conclusions can be drawn from these studies because of their limited sample sizes. A large study by Cohn et al. of 240 Canadian subjects revealed a prevalence rate of 42.6% for males and 48.5% for females (Cohn et al., 2004). These figures are comparable to those found in the CATIE study by McEvoy et al. who found prevalence rates of 36.6% for males and 54.2% for females (McEvoy et al., 2005). To our knowledge, this is the first large sample European study on the prevalence of MetS. In a preliminary report, a prevalence rate of 22% among a sample of 100 patients was found (De Hert et al., in press). We therefore hypothesized that the prevalence rate of MetS for our sample of 430 schizophrenic subjects would be lower than the US and Canadian prevalence rates found by McEvoy et al. and Cohn et al., respectively.