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17-04-2013 | Article

Obesity linked to reduced cognition in schizophrenia


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medwireNews: Patients with schizophrenia who are obese have poorer cognitive function than their normal-weight counterparts, results from a Chinese study show.

Jingping Zhao (Central South University, Changsha) and team found that obese (body mass index [BMI] ≥27.5 kg/m2) schizophrenia patients had poorer scores on tests of executive function, processing speed, and visual memory than healthy-weight (BMI 18.5-22.9 kg/m2) patients.

"Future studies should explore if weight loss and management can improve cognitive function in obese patients who suffer from schizophrenia," write the authors in BMC Psychiatry.

The researchers studied a total of 896 schizophrenia patients, aged 18-50 years, from 10 sites in China. Of the patients, 18.1% were obese, 35.6% were overweight (BMI 23-27.4 kg/m2), 39.9% were of a healthy weight, and 6.4% were underweight (BMI <18.5 kg/m2).

After accounting for gender, the team found that a higher BMI was significantly associated with lower scores on the Visual Reproduction test of the Wechsler Memory Scale-Revised (WMS-R), which assesses visual memory, and the Digit Symbol test of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), which assesses processing speed, as well as a lower composite z score.

Regarding BMI categories, post-hoc analysis revealed that obese patients with schizophrenia had significantly poorer scores than healthy-weight patients on the Trail Making Test B (123.7 vs 106.7 - higher scores equate to poorer performance), which assesses executive function, the WMS-R Visual Reproduction test (8.2 vs 9.3), the WAIS-R Digit Symbol test (44.0 vs 48.3), and the composite z score.

Although there was a significant difference in mean BMI between patients taking typical and atypical antipsychotics (22.9 vs 23.6 kg/m2), there were no significant differences between the two groups regarding measures of cognition.

"To our knowledge, this is the largest study to assess the relationship between obesity and cognitive function in schizophrenia," comment Zhao et al.

They conclude: "Our study suggests that, in addition to its well established risk for various cardiometabolic conditions, obesity is also associated with worse cognitive function in Chinese patients with schizophrenia."

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Mark Cowen, Senior medwireNews Reporter