Key clinical point: High school students who started classes later in the morning slept significantly more on weeknights than their early-starting peers.

Major finding: At 2 years, students saw a mean 43 minutes more daily sleep associated with the delayed start time (P < .001), compared with students whose start time stayed at about an hour earlier.

Study details: An observational cohort study tracking 455 students at five Minnesota schools over 2 years, with objective sleep data from wrist actigraphy.

Disclosures: Dr. Widome and colleagues’ study was supported by a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development; the authors received support from a grant from the Minnesota Population Center. One of the coauthors acknowledged receiving a consulting fee from Jazz Pharmaceuticals.