Factors associated with early response to olanzapine and clinical and functional outcomes of early responders treated for schizophrenia in the People’s Republic of China

BACKGROUND The aims of this analysis were to identify factors associated with early response (at 4 weeks) to olanzapine treatment and to assess whether early response is associated with better longer-term outcomes for patients with schizophrenia in the People's Republic of China. METHODS A post hoc analysis of a multi-country, 6-month, prospective, observational study of outpatients with schizophrenia or bipolar mania who initiated or switched to treatment with oral olanzapine was conducted using data from the Chinese schizophrenia subgroup (n=330). Factors associated with early response were identified using a stepwise logistic regression with baseline clinical characteristics, baseline participation in a weight control program, and adherence with antipsychotics during the first 4 weeks of treatment. Mixed models for repeated measures with baseline covariates were used to compare outcomes over time between early responders and early nonresponders to olanzapine. RESULTS One hundred and thirty patients (40%) achieved an early response. Early response was independently predicted by higher baseline Clinical Global Impressions-Severity score (odds ratio [OR] 1.51, 95% confidence interval [CI] 1.15-1.97), fewer years since first diagnosis (OR 0.94, CI 0.90-0.98), a greater number of social activities (OR 1.22, CI 1.05-1.40), participation in a weight control program (OR 1.81, CI 1.04-3.15), and high adherence with antipsychotics during the first 4 weeks of treatment (OR 2.98, CI 1.59-5.58). Relative to early nonresponders, early responders were significantly more likely to meet treatment response criteria at endpoint, had significantly greater symptom improvement (Clinical Global Impressions-Severity), and had significantly greater improvement in functional outcomes (all P<0.05). CONCLUSION High levels of adherence to prescribed antipsychotics and participation in a weight control program were associated with early response to olanzapine in Chinese patients with schizophrenia. Early response was associated with greater improvement in symptomatic, functional, and quality of life outcomes at 6 months compared with early nonresponse. Current findings are consistent with previous research outside of the People's Republic of China.