Background: Sleep has a major role in daily cycles and reconstruction of physical and mental abilities. Regarding the importance of this feature, we decided to determine sleep quality in medical students.

Methods: A questionnaire containing demographic data, Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index was prepared. We distributed the questionnaires using a census method to every student at the Zanjan Faculty of Medicine. The completed questionnaires were collected and the data was analyzed using SPSS.

Results: A total of 224 students answered the questionnaire, with 133 (59.4%) students evaluated to have good sleep quality and 91 (40.6%) poor sleep quality. Of these 91 students, 38% were female and 44.8% were male (p=0.307). The prevalence of poor sleep quality according to the four stages of medical training was 24.6% of those in basic sciences, 42.9% of those in physiopathology, 41.7% of externs, and 53.5% of interns (p=0.008). According to residential status, the prevalence of poor sleep quality was 61.5% among students living with their spouse, 44.6% for students living in their own private homes, 37.6% among students living in the dormitory, and 20.8% for those living with their parents (p=0.024). According to marital status, 35.8% of singles and 64.9% of married students had poor sleep quality (p=0.001). According to financial status, 57.9%, 46.9%, and 33.9% of those from low, moderate and high economic classes, respectively, were sleep deprived (p=0.049). Among those with average grades of under 16 and over 16 out of 20, 47.5% and 32%, respectively, were suffering from poor sleep quality (p=0.047). There was no obvious relationship between sleep quality and BMI, sex, or history of depression or anxiety.

Conclusion: Poor sleep quality was significantly associated with lower grades, economic status, living arrangement and type of training. A large number of students quality of life and work may suffer because sleep deprivation.