RISK OF DIABETES MELLITUS (DM) appears higher in specific diseased populations. Hung et al. compared a group of antipsychotic-treated Chinese schizophrenia patients with a general population recruited for diabetes study1 and identified a significant increase of incidence of DM in younger patients (aged 20–49 years) but not in elderly (aged 50–69 years).2 Because the authors defined DM using a looser criterion (fasting plasma glucose ≥7.0 mmol/L) but a more stringent definition (2-h oral glucose tolerance test [OGTT]) was used for the reference population, the risk of DM in the schizophrenia patients might be inflated.

Here, we compared the prevalence of impaired fasting glucose (IFG), the pre-diabetic state of a schizophrenia population, with that of the Nutrition and Health Survey in Taiwan conducted between 1993 and 1996 (NAHSIT 1993–1996).3 A broader definition of IFG, that is, fasting plasma glucose ≥6.1 mmol/L, was adopted as reported in other epidemiological studies.4 NAHSIT subjects (989 men, 1159 women) within our defined age strata were compared with the schizophrenia population (369 men, 269 women).

Stratification by sex in the 19–44 age group demonstrated significant differences between the two populations in male patients (odds ratio [OR], 2.95; 95% confidence interval [CI]: 1.13–7.71, P = 0.021) and in female patients (OR, 6.19; 95%CI: 1.37–28.0, P = 0.023) in the risk of IFG; for the age range 45–64 there were no differences either in male patients (OR, 0.86; 95%CI: 0.37–1.96, P = 0.714) or female patients (OR, 1.07; 0.62–1.84, P = 0.802). The IFG prevalence in the schizophrenia population was significantly higher in the male and female patients for the 19–44 age range but not for the 45–64 age group when compared with the NAHSIT.

Our findings are in accordance with those of Hung et al. That the prevalence of IFG in older patients was not different from the elderly in NAHSIT, is possibly because the older strata of both populations carried similar risk of DM, that is, some young normal subjects without DM will develop DM when they get older. A shared biological susceptibility is suggested as demonstrated by an increased risk of DM in non-schizophrenic relatives, and linkage evidence that appears in both schizophrenia and type II DM.5

Received 16 August 2008; revised 2 October 2008; accepted 7 October 2008.


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