1. Adequate sleep: Respondents report how many hours of sleep they usually get, or what time they usually wake up and go to sleep. The National Sleep Foundation (2000) recommends 8.5–10 h of sleep per night for adolescents ages 12–19. Following these recommendations, person-year observations under age 20 are assigned a value of 1 if they report adequate (8–11 h) sleep, and a value of 0 otherwise. For those aged 20 or older, a value of 1 is assigned if adequate sleep (6–9 h) is
reported and 0 otherwise