Associations between sedentary behaviour and metabolic parameters in patients with schizophrenia
Introduction
In recent years metabolic and cardiovascular diseases (CVD) have become a major concern in the multidisciplinary treatment of patients with schizophrenia (Correll, 2007, Fleischhacker et al., 2008, De Hert et al., 2011; Mitchell et al., 2011). Patients with schizophrenia are 1.5–2 times more likely to be overweight, have a twofold increased risk for diabetes and hypertension and show a 5 times higher prevalence of dyslipidemia compared with the general population (De Hert et al., 2009). The metabolic syndrome (MetS) is one of the most widely used markers for cardio-metabolic risk. According to the International Diabetes Federation, MetS is defined as abdominal obesity, low levels of high-density lipoprotein cholesterol (HDL), and elevated triglycerides, blood pressure, and fasting glucose (Alberti et al., 2006). In a recent meta-analysis of 126 analyses in 77 publications (n=25,692), the overall rate of MetS in patients with schizophrenia was 32.5% (95%CI=30.1–35.0%) and there were only minor differences according to treatment setting (inpatient versus outpatient), by country of origin and no appreciable difference between males and females.
The association of schizophrenia with increased cardio-metabolic risk factors is a complex interplay between genetic vulnerability (van Winkel et al., 2010a, van Winkel et al., 2010b), illness related factors (Laursen et al., 2007), effects of antipsychotic treatment (De Hert et al., 2008, Hasnain et al., 2010, Rummel-Kluge et al., 2010) as well as unhealthy lifestyle choices (such as lack of regular physical activity, poor nutrition, high substance abuse, and smoking) (Strassnig et al., 2003, Bobes et al., 2010, Vancampfort et al., 2010). More recently, another lifestyle factor, sedentary behaviour has emerged as an important public health problem. Sedentary behaviour refers to activities that do not increase energy expenditure substantially above the resting level and includes activities such as sleeping, sitting, lying down, watching television, and other forms of screen-based entertainment (Pate et al., 2008). There is a growing body of evidence that sedentary behaviour may, even independent of physical activity, be a distinct risk factor for multiple adverse health outcomes in adults. A recent meta-analysis (Thorp et al., 2011) showed a consistent relationship of self-reported sedentary behaviour with weight gain from childhood to the adult years, weight gain during adulthood, cardio-metabolic risk and mortality. Finding associations for sedentary behaviour with increased BMI and MetS risk in patients with schizophrenia therefore may provide support for prevention strategies including efforts to decrease sedentary behaviour, besides promotion of physical activity. The relationships between sedentary behaviour, MetS and BMI remain however poorly understood in patients with schizophrenia. No evidence is available in patients with schizophrenia on the extent to which overall sitting time (inclusive of leisure-time and transport domains of sedentary behaviour) is associated with MetS and BMI.
The first aim of this study was to examine differences in sedentary behaviour (overall sitting time) between patients with schizophrenia and healthy controls matched for age, gender and body mass index (BMI). The second aim was to investigate associations in patients between overall sitting time, the presence of MetS, BMI and mental health variables and to investigate the extent to which overall sitting time was predictive for MetS and BMI.
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Participants and procedure
Over a 5-month period, consecutive in-patients with schizophrenia of the University Psychiatric Centre of Kortenberg and the Brussels Nighthospital Belgium were invited to participate. Psychiatric diagnosis based on DSM-IV criteria was established by experienced psychiatrists responsible for the patients' treatment. Patients were included if (1) acute symptoms were (at least partially) remitted, and (2) patients were stable on antipsychotic medication, i.e. using the same dosage for at least
Participants
A total of 87 patients with schizophrenia were initially screened. Four persons with co-morbid substance abuse were excluded. Of the 83 eligible patients, another 7 declined to participate. Seventy-six participants were included in the final analysis. Mean duration of illness for these 76 patients was 12.4±9.5 years. Twenty seven patients (35.5%) fulfilled the criteria for MetS (40.9% of the women and 33.3% of the men). An overview of the medication intake is presented in Table 1. Mean daily
Discussion
To the authors' knowledge, the present study is one of the first to demonstrate that patients with schizophrenia spend more time sitting than age, gender and BMI-matched healthy controls, i.e. patients with schizophrenia do watch more hours per day television and/or are more hours per day involved in other forms of screen-based entertainment and/or spend more time sitting during motorised transport. The sedentary nature of our schizophrenia-group confirms the previously observed low energy
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