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Most of us are active by day and rest by night, but within these confines there are several possibilities ranging from larks (early risers) to owls (late risers).
These preferences, called chronotypes, have a genetic basis that controls one’s biological clock, but this can be modified by various factors such as light exposure, age and lifestyle.
However, when the genetic and environmental cues are not aligned a chronic condition known as ‘social jetlag’ may ensue.
This problem is exacerbated during adolescence when chronotypes become increasingly delayed, but schools start early in the morning.
This can cause sleep loss that may lead to major health and psychological problems and also affect academic performance.
In a recent study scientists examined how the interaction between chronotype and school start time influenced individual academic performance* by taking advantage of a high school system where 753 students had been randomly assigned to lessons in the morning (07.45 to 12.05), afternoon (12.40 to 17.00) or evening (17.20 to 21.40).
This enabled the unbiased testing of the effect of chronology and school schedules on academic performance in adolescents aged 13-14 years and 17-18 years.
The results showed that among the early morning group, very few students got adequate sleep.
The larks (early chronotypes) outperformed owls (late chronotypes) in all school subjects and this effect, which increased as students progressed through the school, was most extreme in maths.
This outcome, however, was not evident in those having afternoon schooling, and the situation almost reversed in those receiving evening schooling, where students with later chronotypes performed slightly better in languages than the early chronotypes in the same group.
Clearly academic performance is influenced by biological variation in daily rhythms, to an extent that has previously been underestimated.
The study authors, while conceding that it is impractical to attempt to fully align school timetables to individual chronotypes, suggest that it may be possible to, for example, progressively delay school start times during adolescence.
* Goldin et al. https://doi.org/10.1038/s41562-020-0820-2.