Early birds less prone to depression
Largest study yet links chronotype to mental health
June 14, 2018
Science Daily/University of Colorado at Boulder
A study of 32,000 women found that those with an early chronotype, or sleep-wake preference, were significantly less likely to develop depression.
Middle-to-older aged women who are naturally early to bed and early to rise are significantly less likely to develop depression, according to a new study by researchers at University of Colorado Boulder and the Channing Division of Network Medicine at Brigham and Women's Hospital in Boston.
The study of more than 32,000 female nurses, published in the Journal of Psychiatric Research, is the largest and most detailed observational study yet to explore the link between chronotype, or sleep-wake preference, and mood disorders.
It shows that even after accounting for environmental factors like light exposure and work schedules, chronotype -- which is in part determined by genetics -- appears to mildly influence depression risk.
"Our results show a modest link between chronotype and depression risk. This could be related to the overlap in genetic pathways associated with chronotype and mood," said lead author Céline Vetter, director of the Circadian and Sleep Epidemiology Laboratory (CASEL) at CU Boulder.
Previous studies have shown that night owls are as much as twice as likely to suffer from depression. But because those studies often used data at a single time-point and didn't account for many other factors that influence depression risk, it has been hard to determine whether depression leads people to stay up later or a late chronotype boosts risk of depression.
To shed light on the question, researchers used data from 32,470 female participants, average age 55, in the Nurses' Health Study, which asks nurses to fill out health questionnaires biennially.
In 2009, all the participants included in the study were free of depression. When asked about their sleep patterns, 37 percent described themselves as early types, 53 percent described themselves as intermediate types, and 10 percent described themselves as evening types.
The women were followed for four years to see who developed depression.
Depression risk factors like body weight, physical activity, chronic disease, sleep duration, or night shift work were also assessed.
The researchers found that late chronotypes, or night owls, are less likely to be married, more likely to live alone and be smokers, and more likely to have erratic sleep patterns.
After accounting for these factors, they found that early risers still had a 12 -- 27 percent lower risk of being depressed than intermediate types. Late types had a 6 percent higher risk than intermediate types ( this modest increase was not statistically significant.)
"This tells us that there might be an effect of chronotype on depression risk that is not driven by environmental and lifestyle factors," said Vetter.
Genetics play a role in determining whether you are an early bird, intermediate type, or night owl, with research showing 12-42 percent heritability. And some studies have already shown that certain genes (including PER2 and RORA), which influence when we prefer to rise and sleep, also influence depression risk.
"Alternatively, when and how much light you get also influences chronotype, and light exposure also influences depression risk. Disentangling the contribution of light patterns and genetics on the link between chronotype and depression risk is an important next step" Vetter said.
Vetter stresses that while the study does suggest that chronotype is an independent risk factor for depression, it does not mean night owls are doomed to be depressed.
"Yes, chronotype is relevant when it comes to depression but it is a small effect," she says, noting that her study found a more modest effect than previous ones have.
Her advice to night owls who want to lower their risk?
"Being an early type seems to beneficial, and you can influence how early you are" she said. Try to get enough sleep, exercise, spend time outdoors, dim the lights at night, and try to get as much light by day as possible.
https://www.sciencedaily.com/releases/2018/06/180614212658.htm
Early to bed and early to rise: it's keeping kids leaner
September 30, 2011
Science Daily/American Academy of Sleep Medicine
Researchers recording the bedtimes and wake times of 2,200 Australian youths found that the night owls were 1.5 times more likely to become obese than the early birds, twice as likely to be physically inactive and 2.9 times more likely to sit in front of the TV and computer or play video games for more hours than guidelines recommend.
A study in the Oct. 1 issue of the journal Sleep recorded the bedtimes and wake times of 2,200 Australian participants, ages 9 to 16, and compared their weights and uses of free time over four days. Children who went to bed late and got up late were 1.5 times more likely to become obese than those who went to bed early and got up early. Furthermore, late-nighters were almost twice as likely to be physically inactive and 2.9 times more likely to sit in front of the TV and computer or play video games for more hours than guidelines recommend.
"The children who went to bed late and woke up late, and the children who went to bed early and woke up early got virtually the same amount of sleep in total," said co-author Carol Maher, PhD, a postdoctoral fellow with the University of South Australia. "Scientists have realized in recent years that children who get less sleep tend to do worse on a variety of health outcomes, including the risk of being overweight and obese. Our study suggests that the timing of sleep is even more important."
Maher said mornings are more conducive to physical activity for young people than nights, which offer prime-time TV programming and social networking opportunities. This relationship between time of day and available activities might explain why more sedentary and screen-based behaviors were observed with later bedtimes, she said. At a time when research is showing that teenagers have a natural tendency to stay up late and wake late, the results of this study could stand as a warning.
"It is widely accepted that the sleep patterns of adolescents are fundamentally different from children and adults, and that it is normal for adolescents to stay up very late and sleep in late in the morning," Maher said. "Our findings show that this sleeping pattern is associated with unfavorable activity patterns and health outcomes, and that the adolescents who don't follow this sleep pattern do better."
Other findings from the University of South Australia study:
Early-bed/early-risers went to bed 70 to 90 minutes earlier, woke up 60 to 80 minutes earlier and accumulated 27 minutes more moderate to vigorous physical activity each day than late-risers.
Late-bed/late-risers watched TV, played video games or were online 48 minutes longer each day than early-bed/early risers, primarily between 7 p.m. and midnight.
Only 12 percent of late-bed/late-risers had an average of two hours or less screen time per day, which is recommended for children and teens by the Australian Department of Health and Aging. In comparison, 28 percent of early-bed/early risers met the recommendation for screen time.
On a broad scale, late-bed/late-risers replaced about 30 minutes of moderate to vigorous physical activity with 30 minutes of sedentary behavior each day, relative to the early-bed/early-rise group.
Body-mass index (BMI) scores were higher in late-risers than early-risers, and late-risers were more likely to be overweight or obese. Late-bed/late-risers tended to have few siblings, live in major cities, come from lower household incomes and have a part-time job.
http://www.sciencedaily.com/releases/2011/09/110930052216.htm
Being A Night Owl in High School is Linked with Lower College GPA
June 11, 2009
Science Daily/American Academy of Sleep Medicine
According to a research abstract that will be presented on June 9, at Sleep 2009, the 23rd Annual Meeting of the Associated Professional Sleep Societies, students who consider themselves to be evening types (that is someone who feels more alert and does their best work later in the day) have poorer sleep hygiene scores than morning and intermediate types.
Sleep hygiene is the group of behaviors linked to good sleep and alertness. Examples include having a regular bedtime routine, a regular wake time, a regular bed time, and sleeping in a comfortable bed.
The researchers found that this poor sleep hygiene was related to poorer academic performance and a decline in grade point average (GPA) during the transition from high school to college.
http://www.sciencedaily.com/releases/2009/06/090609072813.htm