Influences of patient-related variables on risperidone efficacy for acutely exacerbated schizophrenia: Analyses with rigorous statistics

Response predictors of risperidone or other newer atypical antipsychotics for schizophrenia treatment remain unclear. This study aimed to investigate the influence of patient demographics on risperidone efficacy for schizophrenia. One hundred twenty-one newly hospitalized patients who had schizophrenia with acute exacerbation entered this prospective, 6-week risperidone trial. The target dose was 6 mg/day, or lower in case of side effects. Consequently, the mean +/- SD dose remained quite stable after week 2 and reached 4.4 +/- 1.3 mg/day at week 6. Efficacy and side effect assessments were conducted biweekly. The mean total score of the Positive and Negative Syndrome Scale (PANSS) declined during the trial, particularly within the first 4 weeks. Further, of the various efficacy scores (and their natural logarithm values) collected, only the logarithm of the PANSS total score was selected to serve as the response value, because it was normally distributed and thus suitable for regression analyses. After adjusting the effects of treatment duration (weeks 0-6) and other patient-related variables with the generalized estimating equation method, each 1-week increase in duration of prior hospitalizations raised the PANSS total by 0.04% (p = 0.002) and each 1-year increment in the education duration decreased the PANSS by 0.94% (p = 0.04). Gender, age, age at illness onset, duration of illness, diagnosis subtype, or number of prior hospitalizations, however, did not significantly impact the response value. These preliminary results suggest that longer hospitalization duration and shorter education predict higher symptomatology. Further studies with longer observation and larger samples in not only acutely ill patients but also other populations (e.g., first-episode patients) are warranted.