Differential trends in prevalence of diabetes and unrelated general medical illness for schizophrenia patients before and after the atypical antipsychotic era

Abstract 

Objective

To estimate the net growth in the risk of type 2 diabetes mellitus (DM) in the population of patients with schizophrenia that may be attributable to the increased use of the class of atypical antipsychotics (A-APDs), adjusting for community trends in DM risk.

Methods

Using data from the National Hospital Discharge Survey, we perform trend analyses for prevalence of DM and general illness unrelated to insulin resistance in patients with schizophrenia, as well as in individuals without known mental illness, during three time periods: 1) prior to any A-APDs introduction (1979–1989); 2) short-term after their introduction (1990–1995), and long-term following their introduction (1996–2001).

Results

Trends in DM and general illness risks were comparable among inpatients with schizophrenia and those without mental illness during the pre-A-APD era and the short-term post-A-APDs era. During 1996–2001, the net difference in DM prevalence grew at an increasing rate (0.7% per year, p<0.001). By 2001, over a base DM prevalence of 10% in patients with schizophrenia, 3.1 percentage points (p=0.016) could be attributed to the use of A-APDs. There was no significant net growth in the prevalence of general illness during this period for these patients. This growth was most pronounced among African-American females and middle aged (35–49 years old) patients. This increased risk of DM translates into additional direct medical costs of $800 million per year.

Conclusions

The introduction of A-APDs, after a lag period, is associated with increased risk of DM. This needs to be considered in light of the advantages of these drugs in efficacy and tolerability. Long-term studies are necessary to identify the effect of individual A-APDs on DM risk.

Keywords: Atypical antipsychotics, Schizophrenia, Diabetes prevalence, Costs