According to the results of a study published in the Journal of Clinical Psychiatry, more than a third of psychiatric inpatients on antipsychotic drugs meet American Diabetes Association (ADA) criteria for pre-diabetes.

The authors note that there is a vast body of literature identifying patients treated with second-generation antipsychotics as a group at high risk of developing type 2 diabetes mellitus, mainly due to the weight gain seen during treatment with these drugs.  They say that the identification of pre-diabetes and its proper management could mitigate the adverse metabolic effects of antipsychotics, and potentially prevent the development of diabetes and its complications in this patient group.  The purpose of their study was to establish the prevalence of pre-diabetes in a cohort of psychiatric inpatients receiving antipsychotics and to compare the clinical and metabolic features of patients with pre-diabetes to those with normal glucose tolerance and those with diabetes mellitus. 

The study included a total of 783 patients without a history of diabetes who were admitted to a psychiatric centre in Belgium between 2003 and 2007, who were treated with antipsychotics, and who agreed to routine metabolic screening.  The participants had a mean age of 37 years and 60% were male.  The majority had schizophrenia (70%) or schizoaffective disorder (13%) and most were treated with second-generation antipsychotics (94.5%).  Over half were overweight (37%) or obese (21%).

According to the ADA criteria, 290 patients (37%) had pre-diabetes (fasting glucose of 100-125mg/dL, or 140-199mg/dL at two hours after an oral 75-g glucose tolerance test, or haemoglobin A1c of 5.7%-6.4%) and 80 (10%) had newly diagnosed diabetes.  Compared to patients with normal glucose tolerance, those with pre-diabetes were older and had a higher body mass index and prevalence of overweight and obesity, higher insulin levels and resistance to insulin, and an increased prevalence of metabolic syndrome.  Those with pre-diabetes were more likely to be treated with clozapine than patients with normal glucose tolerance (13.3% versus 9.7%; p=0.001); the groups were similar with respect to other antipsychotics.            

The authors note that the use of metformin for the prevention of diabetes is not approved, but is proposed by expert panels.  They suggest that it may be particularly beneficial in psychiatric patients whose pre-diabetes has been produced by antipsychotic weight gain.  They add that their results "should further stimulate concerted efforts toward widespread cardiometabolic monitoring, which has remained inadequate, as well as toward more aggressively preserving or restoring glucose tolerance, insulin sensitivity, and overall metabolic health."