Relationship between the use of seclusion and mechanical restraint and the nurse-bed ratio in psychiatric wards in Japan.

The relationship between the number of nurses in psychiatric wards and frequency of use of seclusion and restraint has been unclear. We aimed to clarify this relationship in Japanese general psychiatric wards while controlling for patient and ward-level characteristics. We hypothesized that seclusion and mechanical restraint are less likely to be used in a ward with more nurses. We used data for individual admissions from April 2015 to March 2017 in hospitals participating in the Psychiatric Electronic Clinical Observation (PECO) system, which extracted data from each hospital's electronic health record system. We analyzed the data of 10,013 admissions in 113 wards of 23 hospitals. We examined the relationships between the number of nurses per 10 beds in each ward and the use of seclusion and mechanical restraint, controlling for the patients' age, sex, diagnosis, voluntary versus involuntary admission, prescribed dose of antipsychotics, severity of symptoms, and length of stay, in addition to ward-level characteristics including ward size, location (urban or rural), and type of ward (acute ward or not), using multilevel multivariate logistic regression analyses. The fraction of admissions exposed to at least one episode of seclusion or mechanical restraint was 36.7% and 14.9%, respectively. The odds ratios of the number of nurses per 10 beds for the use of seclusion and mechanical restraint were 2.36 and 1.74, respectively, indicating that both seclusion and mechanical restraint were actually used more frequently in wards with more nurses. A possible explanation is that patients anticipated to need coercive measures are more likely to be admitted to wards with many nurses. Increasing the number of nurses in a ward may not contribute to reducing the use of seclusion and restraint.