Early to bed okay, but early to rise might not make Jack a bright boy

Researchers in the U.S. say that an early start to school classes in the mornings means many teenagers lose much needed sleep and that makes them more likely to be moody and perform poorly in school.

In a study by researchers at Northwestern University and Evanston Township High School in Illinois of students aged 12 to 15 years old, the researchers found they lost an average of two hours of sleep on the nights before a school day, affecting their work and alertness in class.

In an earlier survey in 2003 it was found that 85 percent of high schools begin the day before 8:15 and more than one-third of high schools rang the bell to begin classes at 7:30 a.m. or earlier. This often meant students living long distances from school faced even earlier wake-up calls to catch rides.

According to the researchers sleepiness is linked to moodiness and poor school performance, and a chronic shortage of sleep correlates with a greater propensity to take up smoking or to be involved in car crashes.

Adolescents when they enter high school are at a time in their lives when their bodies are undergoing changes to their biological clocks called circadian rhythms, that govern when they become sleepy and fully awake. These changes say the researchers, tend to make them go to bed later and wake up later.

In the study, 60 teens kept sleep diaries during a month in summer when schools were closed and again during a few months of the school year.

It was found that while they lost sleep on school nights, they slept 30 minutes longer than usual on weekend nights during the school year and on summer nights, which indicated they were not just using weekends to catch up on sleep during the school year.

The research team say the weekend sleep and weekend wake times may represent a return to an intrinsic circadian rhythm that is lost during the week because of the imposed school schedules.

The findings point to sleepy students in the mornings who tend to become more alert in the afternoons.

Teachers in an accompanying report agreed with the study in this respect.

The report which is published in the journal Pediatrics was written by pediatric sleep experts.