PROJECT SUMMARY
Although the National Sleep Foundation recommends 8.5 to 9.25 hours of sleep per night for adolescents, more
than half of US 16-year-olds regularly get less than seven hours; further, girls and disadvantaged youth are at
even greater risk for short sleep duration. “Sleep debt” has consequences that extend far beyond hampering
day-to-day functioning as it is deleterious to multiple areas health and wellbeing. While a variety of forces such
as screen time, homework expectations, and other factors can be implicated in stymying American teenagers’
sleep, studies have revealed that early high school start times, which are asynchronous with adolescent biology,
are one of the most significant obstacles to youth being able to net sufficient sleep. When children begin
puberty, circadian rhythms shift such that melatonin is secreted later in the evening making it difficult to fall
asleep before 11pm. This neurobiological change means that adolescents who attend “early-start” (prior to
8:30am) high schools, even those who strive for an early bedtime, will struggle to get sufficient sleep. Natural
experiments have clearly shown that later school starts allow adolescents a greater opportunity to accumulate
adequate sleep, but unfortunately most US schools start before 8:30am. We hypothesize that the benefits of
later high school start times may extend to promoting school success, which in turn could have numerous long-
term benefits as low educational attainment is a profound contributor to population-level morbidity and
mortality from cardiovascular disease (CVD). We propose secondary analyses of data from the START study
(R01 HD088176). START is an existing cohort designed to evaluate the impact of a natural experiment in
school schedule modification on weight and weight-related behavior change over time. At baseline (Spring
2016), START recruited ninth grade students from five Minnesota high schools with early start times (7:30 or
7:45am). In the second and third years of the study (school years 2016/17 and 2017/18), two of the five schools
had delayed their start time by 50 or 55 minutes while three remained at 7:30am. Surveys on the full sample (n
= 2,422) and an object sleep measures subsample (n = 455) were collected annually. After planned START data
collection was completed, we obtained additional data from schools on student academic achievement and
behaviors that was individually linkable to START data. Our specific aims are: 1) Identify the impact of high
school start time on school performance and behaviors over time. 2) Determine how objectively measured
features of sleep (duration, timing, and quality) relate to school performance and behaviors over time. The
products of this line of research have potential for public health impact because they will characterize
associations between sleep policy and school success. It may also provide evidence for whether certain school
schedules might amplify student performance and wellbeing in ways that could reduce long-term
cardiovascular risk. If effective, later school start times, a policy that is deployable in a wide range of
communities across the US, could enhance the health-promoting effectiveness of education.
