The Pittsburgh Sleep Quality Index (PSQI)
The Pittsburgh Sleep Quality Index (PSQI) is an instrument with seven components (sleep quality, delay in falling asleep, the sleep duration, the sleep efficiency, sleep disorders, consumption of sleep-inducing medications, and the daily performance) and 18 questions. The score of every item in this questionnaire is between 0 and 3. The sum of the scores means of seven components was used as index of sleep quality (5).