Multiple positive outcomes of a later school starting time for adolescents

For Whom (and When) the Time Bell Tolls: Chronotypes and the Synchrony Effect

Circadian rhythms are powerful timekeepers that drive physiological and intellectual functioning throughout the day. These rhythms vary across individuals, with morning chronotypes rising and peaking early in the day and evening chronotypes showing a later rise in arousal, with peaks in the afternoon or evening. Chronotype also varies with age from childhood to adolescence to old age. As a result of these differences, the time of day at which people are best at attending, learning, solving analytical problems, making complex decisions, and even behaving ethically varies. Across studies of attention and memory and a range of allied areas, including academic achievement, judgment and decision-making, and neuropsychological assessment, optimal outcomes are found when performance times align with peaks in circadian arousal, a finding known as the synchrony effect. The benefits of performing in synchrony with one's chronotype (and the costs of not doing so) are most robust for individuals with strong morning or evening chronotypes and for tasks that require effortful, analytical processing or the suppression of distracting information. Failure to take the synchrony effect into consideration may be a factor in issues ranging from replication difficulties to school timing to assessing intellectual disabilities and apparent cognitive decline in aging.

Impact of delaying high school start times on weight and related behaviors - the START study

In the US, few adolescents get adequate school night sleep, largely due to early school start times. In the START study we aimed to test the following hypothesis: That following the implementation of later high school start times students have lesser longitudinal increases in body mass index (BMI) and shift to more healthful weight-related behaviors relative to students attending schools that retain early start times. The study enrolled a cohort of students (n = 2426) in five high schools in the Twin Cities, MN metro. Heights and weights were measured objectively, and surveys were administered annually from 9th through 11th grades (2016-2018). All study schools started early (either 7:30 am or 7:45 am) at baseline (2016). At follow-up 1 (2017) and continuing through follow-up 2 (2018), two schools delayed their start times by 50-65 min, while three comparison schools started at 7:30 am throughout the observation period. Using a difference-in-differences natural experiment design, we estimated differences in changes in BMI and weight-related behaviors over time between policy change and comparison schools. Students' BMIs increased in parallel in both policy change and comparison schools over time. However relative to changes in comparison schools after the start time shift, students in policy change schools had a modestly more healthful profile of weight-related behaviors - for instance they had a relatively greater probability of eating breakfast, having supper with their family, getting more activity, eating fast food less frequently, and eating vegetables daily. Later start times could be a durable, population-wide strategy that promotes healthful weight behaviors.

Self-perceived rhythmicity in affective and cognitive functions is related to psychiatric symptoms in adolescents

The objective of this study was to evaluate the relationship between self-perceived rhythms measured using the Mood Rhythm Instrument for adolescents (MRhI-Y) and depressive and psychiatric symptoms measured with the Children's Depressive Instrument (CDI) and the Strengths and Difficulties Questionnaire (SDQ). In this study, 186 adolescents were recruited in Rio Grande do Sul, Brazil. We performed a Spearman correlation analysis to evaluate the relationships between quantitative variables. All variables that had a statistically significant correlation were included in ANOVA multiple regression models. The dependent variables in the multiple regression analyses were CDI score and total and emotional scores on the SDQ. We found that only Cognitive self-perceived rhythmicity contributed significantly to the first multiple regression with CDI as the outcome variable. The second regression with SDQ Emotional score as the outcome variable showed that female sex, age, and self-perceived affective rhythmicity contributed significantly to the model. The third regression with SDQ total score as the outcome variable showed that chronotype, self-perceived cognitive symptoms, and affective rhythmicity contributed significantly to the model. In conclusion, we found that lower self-perceived rhythmicity in cognitive factors and higher self-perceived rhythmicity in affective factors were related to presence and intensity of psychiatric and depressive symptoms.