Methods This cross-sectional study was conducted from mid-July to September 2013 in
Hokkaido Prefecture, Japan. Questionnaires were distributed to 1,245 teachers in public junior
high schools. Information about basic characteristics including working hours, and responses to
the Pittsburgh Sleep Quality Index were collected anonymously. Multiple logistic regression
analysis was used to calculate odds ratios (ORs) for the association between long working hours
and sleep problems separately by sex