BACKGROUND : Previous studies have suggested positive association between residents' workload and medical errors. However, few studies have investigated the possible associations between procedural errors, workload, and the individual characteristics of residents, including personality, mental state and job satisfaction.
OBJECTIVE : To explore possible associations of workload and individual characteristics of residents with their procedural error rates.
DESIGN : Prospective observational study based on a daily questionnaire.
PARTICIPANTS : Residents of postgraduate year 1 and 2.
MEASUREMENTS : Residents' workload (on-calls, work hours, sleep and napping hours), residents' physical and mental health state, personality inventory, and procedural error rate (defined as procedural error counts divided by overall procedural attempts).
RESULTS : On average, the residents (N=49) were responsible for 9.8 inpatients per day (range, 1.9-23.1), worked for 16.0 hours per day (range, 12.6-19.8), slept for 4.4 hours per day (range, 2.8-5.7), napped for 0.2 hours per day (range, 0-0.7), and experienced 1 overnight work shift every 7.2 days. The procedural error rate was 2.2 per 10 procedures (range, 0.4-5.0). Using a multivariable adjusted regression model, significant factors associated with lower error rates included : longer napping ; reflective personality ; better mental state ; higher job satisfaction ; and, less on-call frequency.
CONCLUSIONS : Procedural error of residents is positively associated with higher on-call frequency and inversely associated with napping, reflective personality, better mental state, and higher job satisfaction. For reducing procedural error among residents, improvement of modifiable factors, such as workload and mental health, is needed.

OBJECTIVE : This study was conducted in a Japanese population to better understand the association between insomnia and sleeping prone.
METHODS : A cross sectional questionnaire study was conducted with outpatients of St. Luke's International Hospital in August, 2007. Information on sleep position habits, symptoms, quality of life, and sleep quality was collected. The Athens Insomnia Scale (AIS) was used to measure sleep quality. Participants with an AIS score of 4 or higher were categorized as sub-threshold insomnia and as the insomnia group.
RESULTS : Of the 784 subjects who returned completed questionnaires (response rate=65%) 30.4% were men. About 13% of the respondents slept in the prone position at least three times a week. Based on multivariate adjusted logistic regression analysis, there was a significant association between sleeping prone and having no problem with insomnia (odds ratio, 0.61 ; 95% CI, 0.38-0.99).
CONCLUSION : These data suggest that sleeping in the prone position is associated with good quality sleep.