Hong Kong J Psychiatry 2008;18:81


Body Mass Index and Waist Circumference among Patients with Schizophrenia

To the Editor — I read with interest the recent cross-sectional study by Ainsah et al1 of the anthropometric measurements among patients with schizophrenia. I am concerned that their findings may be affected by its methodological limitations.

Information about the sampling method and response rates was missing; this would affect optimal estimation of the prevalence rate of obesity and overweight among patients with schizophrenia. The young age (44% being younger than 30 years) and high level of education (40% having studied to the tertiary level) may reflect a biased sample. This may underestimate the prevalence of obesity and overweight among patients with schizophrenia in the general psychiatric setting.2,3 The major limitation is their use of bivariate analysis. The comparison of body mass index and waist circumference between patients receiving various types of antipsychotics could be confounded by many factors, e.g. gender and duration of treatment. Regression analysis would be an option to model the relationship between these variables.

Body mass index and waist circumference are anthropometric measures, which are useful in the assessment of obesity and its related health risk.4 Body mass index correlates with body fat, morbidity and mortality, while waist circumference indicates the abdominal fat distribution.4

Lower body mass index on olanzapine and clozapine are inconsistent with large-scale prospective study.5 The causal relationship could be better estimated by changes in body mass index and waist circumference, which was not addressed in the cross-sectional design. Other shortcomings included the difference in proportion of patients taking weight-gaining antipsychotics between their groups, which could lead to different results in comparison to those in receipt of more conventional and atypical antipsychotics.6

Without doubt, investigation of physical factors affecting co-morbidity among psychiatric patients would reveal the extent of this important but neglected problem in Asia. Hopefully, this study will help stimulate future local research in this field.

Dr Edwin Lee, MSc, MBChB, MRCPsych
E-mail: elee@cuhk.edu.hk
Department of Psychiatry
The Chinese University of Hong Kong
Hong Kong, China


  1. Ainsah O, Salmi R, Osman CB, Shamsul AS. Relationships between antipsychotic medication and anthropometric measurements in patients with schizophrenia attending a psychiatric clinic in Malaysia. Hong Kong J Psychiatry 2008;18:23-7.
  2. Homel P, Casey D, Allison DB. Changes in body mass index for individuals with and without schizophrenia, 1987-1996. Schizophr Res 2002;55:277-84.
  3. Shrewsbury V, Wardle J. Socioeconomic status and adiposity in childhood: a systematic review of cross-sectional studies 1990-2005. Obesity (Silver Spring) 2008;16:275-84.
  4. Aronne LJ. Classification of obesity and assessment of obesity-related health risks. Obes Res 2002;10(Suppl 2):S105-15.
  5. Lieberman JA, Stroup TS, McEvoy JP, Swartz MS, Rosenheck RA, Perkins DO, et al. Effectiveness of antipsychotic drugs in patients with chronic schizophrenia. N Engl J Med 2005;353:1209-23.
  6. Allison DB, Mentore JL, Heo M, Chandler LP, Cappelleri JC, Infante MC, et al. Antipsychotic-induced weight gain: a comprehensive research synthesis. Am J Psychiatry 1999;156:1686-96.
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