Melbourne secondary students to be part of long-term study into sleep, body clock, mood, and academic performance

Adolescence is a crucial time for brain and social development, yet it is also a time when a teen’s body clock naturally becomes later, causing their sleep patterns to change substantially. Sleeping later, having less sleep and irregular sleep-wake patterns are thought to contribute to increased sleepiness, inability to concentrate, negative mood and poor mental health.

Researchers at Monash University are recruiting Year 8 students from Melbourne high schools to participate in a long-term study tracking adolescents’ sleep, body clock, and a range of other outcomes. Importantly it will also test the impact of evening exposure to light on both academic performance and mood. This is particularly relevant at the time of digital age, when 82 per cent of children in Australia aged 12–13 years regularly use a smartphone and 71.5 per cent of adolescents reported using at least one light-emitting electronic device in the hour before bed.

The Circadian Light in Adolescence, Sleep and School (CLASS) Study based at the Turner Institute for Brain and Mental Health is dual funded by the Australian Research Council and National Health and Medical Research Council. The study follows adolescents from Year 8 to Year 12, and assess sleep, body clock, light exposure, and a range of mental health and cognitive functioning outcomes every 6 to 12 months.

According to Dr Julia Stone, Research Fellow and Project Lead, during adolescence, sleep and circadian timing shift later, contributing to restricted sleep duration and irregular sleep-wake patterns. “The association of these developmental changes in sleep and circadian timing with cognitive functioning, and consequently academic outcomes, has not been examined prospectively. The role of ambient light exposure in these developmental changes is also not well understood,” she said.

“We will study these to determine their impact on academic performance and mental health.”

According to the Turner researchers, who recently published the study protocol in the journal, British Medical Journal Open, a key feature of adolescent sleep is a progressive delay in bed and wake times, which is exacerbated on weekends and during vacation, when sleep schedules are less prescribed with sleep before non-school days often 2 or more hours later than on school nights, with longer total sleep time. “These developmental processes interact with early school start times, leading to these large differences in sleep-wake timing as adolescents alternate between school and non- school days,” Dr Stone said.

Among adolescents, developmental changes in circadian and sleep characteristics are associated with:

  • increased daytime sleepiness (reported by nearly 50 per cent of adolescents aged ~14 years)
  • reduced alertness and sustained attention
  • poorer academic performance.

The study will also test evening exposure to light, in particular short wavelength (blue) light, which is known to impact the setting of the circadian clock. “Light exposure during the evening and early night, even at levels typically experienced in indoor settings, delays the circadian clock and suppresses the synthesis of melatonin. Light is also a stimulant, increasing alertness directly, with responses persisting for several hours after lights are turned off, leading to taking longer to fall asleep and reduced restful slow-wave sleep,” Dr Stone said.

“These effects may be particularly pronounced during adolescence, as circadian sensitivity (measured via melatonin suppression) to evening light exposure is increased during early-mid puberty compared with late puberty.” Electronic devices such as smart phones emit bright and blue enriched light and are used close to the eyes.

The CLASS study is currently recruiting Year 8 participants.
To find out more about the study and participate, see the study webpage here: Class Study Monash.

Read the full paper in British Medical Journal:

About Monash University

Monash University is Australia’s largest university with more than 80,000 students. In the 60 years since its foundation, it has developed a reputation for world-leading high-impact research, quality teaching, and inspiring innovation.

With four campuses in Australia and a presence in Malaysia, China, India, Indonesia and Italy, it is one of the most internationalised Australian universities.

As a leading international medical research university with the largest medical faculty in Australia and integration with leading Australian teaching hospitals, we consistently rank in the top 50 universities worldwide for clinical, pre-clinical and health sciences.

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