Background:
Cognitive impairment in
schizophrenia can result in considerable difficulty in performing functions of daily life or social rehabilitation.
Cognitive impairment in
schizophrenia is related to various factors, such as the psychotic severity, aging, medication, and
brain-derived neurotrophic factor (
BDNF). To date, however, no studies investigating the impact of these factors on cognitive functioning in chronic
schizophrenia patients have been performed. Objective: The aim of this study is to identify those factors that influence the cognitive functioning in patients with chronic
schizophrenia. Methods: Sixty-five of 116 long-term hospitalized chronic
schizophrenia patients (63.8 ± 12.1 years old, M/F = 29/36) were enrolled this cross-sectional study. We investigated the relationship among the patients' age, psychotic severity, treatment medication, serum
BDNF levels, and cognitive functioning (measured by the Japanese-language version of the Brief Assessment of Cognition in
Schizophrenia; BACS-J). Additionally, we performed a multivariable linear regression analysis. Results: According to the partial correlation analysis, certain parameters [i.e., age,
chlorpromazine (CP) equivalent,
biperiden (BP) equivalent, and serum
BDNF] were significantly correlated with cognitive functioning, including working memory (WM), motor function (MF), attention and processing speed (AP), and executive function (EF). For the multivariate analysis, the MF component, which had the highest correlation, was selected as the dependent variable, and the independent variables included age, Manchester Scale for chronic
psychosis (ManS) total score, CP equivalent, BP equivalent, serum
BDNF, estimated full scale IQ, and years of education. According to the multiple regression analysis of this model, R (multiple regression coefficient) was 0.542, the adjusted R2 (coefficient of determination) was 0.201, and only BP equivalent (β = -0.305, p = 0.030), but not age, ManS score, CP equivalent, or serum
BDNF, could significantly explain MF at the 5% significant level. Conclusion: In conclusion, aging, medication (administering more
antipsychotics or
anticholinergics), and serum
BDNF concentration are significantly correlated with
cognitive dysfunction in chronic
schizophrenia patients but not with the severity of psychotic symptoms. Furthermore, only the
anticholinergic dosage had a significant causal relationship with MF. Thus, the use of
anticholinergics in chronic
schizophrenia patients with deteriorating cognitive functioning must be reconsidered.