The influence of study design on the results of pharmacoepidemiologic studies of diabetes risk with antipsychotic therapy.
BACKGROUND
Retrospective large patient database studies have reported conflicting findings regarding diabetes risks associated with antipsychotics. This study compared two study designs to assess antipsychotic-related diabetes risk.


METHODS
Claims data were analyzed for over 60,000 patients with psychosis, both treated and untreated with antipsychotics, between January 1999 and April 2002. Diabetes odds ratios for patients treated with antipsychotics versus untreated patients were estimated. All patients and patients stratified by low, medium, and high antipsychotic dose were analyzed. Logistic regression controlled for age, sex, type of psychosis, length of observation/treatment, preexisting excess weight, and use of other drugs.


RESULTS
Under a less rigorous study design, diabetes risk was statistically significant with all antipsychotics versus no treatment. Under a more rigorous design, relative odds for quetiapine and risperidone declined and became statistically nonsignificant, whereas those for olanzapine and conventional antipsychotics increased and remained significant. By dose, only quetiapine showed a lack of statistical significance at all dose levels.


CONCLUSIONS
In database studies estimated risks of antipsychotic-related diabetes are affected by study design. With a more rigorous design, the risk associated with quetiapine and risperidone was not significantly different from that in untreated patients. These findings may explain inconsistent findings in pharmacoepidemiologic database studies.
Gianfrancesco
Frank
F
HECON Associates, Inc., Montgomery Village, MD, USA. heconassoc@aol.com
Wang
Ruey-Hua
RH
Nasrallah
Henry A
HA
D016907:Adverse Drug Reaction Reporting Systems / Q000706:statistics & numerical data; D000368:Aged; D014150:Antipsychotic Agents / Q000009:adverse effects* / Q000627:therapeutic use; D015982:Bias; D003924:Diabetes Mellitus, Type 2 / Q000139:chemically induced* / Q000453:epidemiology*; D003987:Dibenzothiazepines / Q000009:adverse effects / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D017891:Pharmacoepidemiology; D011618:Psychotic Disorders / Q000188:drug therapy* / Q000453:epidemiology*; D000069348:Quetiapine Fumarate; D012107:Research Design; D012189:Retrospective Studies; D018570:Risk Assessment / Q000706:statistics & numerical data*; D018967:Risperidone / Q000009:adverse effects / Q000627:therapeutic use; D014481:United States
D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D000069348:Quetiapine Fumarate; D018967:Risperidone