Background: Cognitive dysfunction is considered to be the core symptom of schizophrenia and cognitive function measurement is considered to be an indispensable test for grasping the condition and prognosis of a patient with schizophrenia. However, the results of cognitive function tests are affected not only by the state of schizophrenia, but also by various clinical features, such as age, sex, duration of disease, and antipsychotic drug dosage, as reported in overseas studies. Unfortunately, few studies have investigated this area in Japan. Therefore, in this study, we examined the influence of clinical features on the results of a cognitive function examination for Japanese patients with schizophrenia.
 Method: We investigated each subtest raw score, sum raw score and composite score of the Brief Assessment of Cognition in Schizophrenia (BACS Japanese version) from the medical records of 111 patients with schizophrenia (40 men, 71 women). These patients were admitted to the department of psychiatry, Niigata University Medical and Dental Hospital, between October 2010 and March 2015. We also examined their age, sex, age of onset, duration of illness, years of education, antipsychotic medication dose, presence or absence of anticholinergics and benzodiazepines (BZD) and Brief Psychiatric Rating Scale (BPRS) score. To investigate the relationship between these features, multiple regression analysis was conducted. This research was approved by the Ethics Committee of Niigata University School of Medicine.
 Result: The results of multiple regression analysis revealed that verbal memory was significantly affected by duration of illness (R²=0.066, P=0.004). Working memory was affected by being male, years of education, and duration of illness (R²=0.178, P=2.49E-5), while motor function was affected by BPRS score and years of education (R²=0.088, P=0.003). Attention and processing speed was affected by BZD, years of education and age (R²=0.161, P=7.01E-5), and executive function was affected by being male, years of education and age (R²=0.209, P=3.37E-6). Sum raw score was affected by years of education, age and BZD (R²=0.183, P=1.80E-5), and finally, verbal fluency was not found to be significantly affected by any clinical features.
 Conclusion: This is a study on Japanese schizophrenia patients who are hospitalized in the relatively acute phase, using the BACS Japanese version, and there have been no reports of research on these groups in Japan. From the results of this study, it became clear that, even in these groups, various clinical features affect the cognitive function of Japanese schizophrenic patients.
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