Circadian Signs Found in Hair Samples

You can find out a lot about a person’s health just by taking a hair sample. Employers and police use hair tests to detect traces of alcohol, cocaine, marijuana, meth and many more oft-abused substances. Your doctor can tell you if you have any vitamin, mineral or nutritional deficiencies from a few dozen strands. And now researchers are learning hair tests can show when we are supposed to sleep and whether our body clocks are off track.

Findings published in the Proceedings of the National Academy of Sciences suggest hair sample testing may help specialists in sleep medicine diagnose circadian rhythm disorders. Hair follicle cells from the head or chin hair contain clock gene expressions. In other words, the amount of the genetic material RNA in your hair shows whether you’re supposed to be alert. Your hair has the most RNA during peak hours.

The Japanese authors repeatedly took hair samples from volunteers as they continued their daily routines. Over the course of three weeks they adjusted their schedule by four hours. Hair samples show their peak activity was still about two hours off, meaning their body clocks weren’t adjusted to the new sleep schedule.

The effect was magnified for rotating shift workers. Their body clock differed from their sleep-wake schedule by an average of five hours.

Beard hair worked best for the tests: researchers needed only three strands to detect circadian rhythms. It took about five head hairs for people with thick hair and up to 20 for thin head hair.

The technique is still in its infancy but has potential for clinical use, the authors argue. Hair samples could potentially tell us our chronotype and diagnose circadian rhythm disorder, jet lag and shift work disorder.

Read more about chronotypes and shift work on the Sleep Education Blog.

Image by Sciencehealth

Morning Larks Lead Better Careers, Chronotype Expert Claims

The business world wakes up bright and early and the evening types have no choice but to fight their natural inclination to keep up with competition. For this reason it’s the morning types that hold an advantage at the office. The body of research by chronotype expert Christoph Randler suggests people who reach their peak performance in the a.m. hours seem to be better positioned for career success.

Randler was featured this month in the Harvard Business Journal’s “Defend Your Research” series. His latest research concludes morning larks are more likely to be of the “take charge” type. A sample of 367 college students responded to surveys with questions about when they tend to be most energetic and whether they are willing and able to take action to change a situation to their advantage. The students who reported they are at their best in the morning hours more often agreed with proactive statements about themselves.

He said its proactivity that leads to better job performance, greater career success and higher wages. Randler’s earlier studies suggest the advantage starts in school. The morning bell rings bright and early at most schools, and from a young age the morning types benefit. They tend to get better grades, which gets them into better colleges and then nets them better jobs out of school. They’re poised to start work early at a high level of performance once they join the 8 to 5 business world.

Despite how it sounds, evening people aren’t condemned to a life of destitution. Research shows they’re often smarter, creative, more outgoing and have a better sense of humor than their button-down counterparts. They can thrive given a more suitable schedule and environment.

These sweeping statements are a bit of a simplification, Randler admits. Evening types can be proactive and some can slightly shift their daily sleep-wake schedules without difficulty. Other research shows our chronotypes shift towards the mornings as we age. The effect may be due to the adult responsibilities such as working and raising children.

If you don’t know whether you’re a morning or evening type there’s an easy way to tell, Randler states. Evening chronotypes sleep in an average of two hours longer on weekends, while morning chronotypes are up bright and early as usual.

Image by Joey Parsons

Are the best and brightest natural night owls?

Our society seems to celebrate the ambition of early risers. We tend to admire the person who’s out on a seven mile jog at the crack of dawn or the employee who’s firmly planted at their desk long before everyone else arrives.

The night owl, who sleeps through most of the morning, is viewed as lazy or irresponsible at best, drunks or criminals at worst.

Do we have it all wrong? Evolutionary psychologist Satoshi Kanazawa poses that question in the latest entry in his blog The Scientific Fundamentalist.

He hypothesized the most intelligent American children grow up to sleep in later their peers. The author looked at the possible relationship between early childhood IQ scores and reported bedtimes in early adulthood.

Kanazawa classified children into five categories according to their IQ scores. Children with IQ less than 75 were considered very dull, above 125 were called very bright. Those in the middle of the bell curve, with a score around 100 were considered average.

You can see in the charts below, the higher the childhood IQ scores the more likely the subjects were to stay up later in early adulthood.





While the data suggests the smartest people turn out to be night owls and the least intelligent end up as larks, there might be more to this relationship than the author lets on. In his entry he fails to define early adulthood. If this includes people around the ages of 18-25 there may be some lifestyle factors at play.

College students are notorious for their nocturnal tendencies. Most Americans of above average intelligence pursue some form of higher education. Many of the most gifted go on to get Master’s degrees or PhD’s, extending that lifestyle by 2-6 years.

Those that choose to go straight into the workforce after high school don’t have the luxury of making their own schedule and sleeping in like college students. They jump right into working the typical 8-5, or even early bird hours, in the case of some blue collar jobs like manufacturing.

Regardless of if the hypothesis is true both chronotypes still come with downsides. Evening-types have a higher risk of severe depression symptoms. Larks may never reach a level of maximum performance during the day.

Contrary to traditional wisdom, morning types were found to be no healthier, wealthier, or wiser than night owls.

It’s best to follow your instincts when it comes to your sleep schedule. Trying to switch from night owl to lark may end up cutting into length of sleep, ultimately doing more harm than good.

Your Sleep Personality Type

A new study examined how your natural sleep preference may be related to your personality type.

The study from Spain involved 862 college students. They were between the ages of 18 and 30.

They completed a short version of the Morningness-Eveningness Questionnaire (MEQ). It measures your circadian “chronotype” – your preferred sleep schedule.

Some people have a circadian clock that makes them “evening types.” These “owls” have a natural tendency to stay up late at night and sleep late in the morning. In contrast “morning types” are “larks” who prefer to go to bed early and wake up early.

The students also completed a short version of the Temperament and Character Inventory (TCI). It measures seven dimensions of personality.

Results show that women had higher TCI scores for harm avoidance, reward dependence and cooperativeness. Men had higher scores for novelty seeking.

How did sleep preference and personality type interact? Evening types had higher scores for novelty seeking. People with this personality type tend to be curious, impulsive and easily bored.

Only men who were evening types had both a lower harm avoidance score and a higher novelty-seeking score. People who are low in harm avoidance tend to be carefree, energetic and outgoing.

Last year a study reported that people who are “evening types” have a higher risk of severe depressive symptoms. Another study suggested that morning types may never reach a level of maximum performance during the day.

Learn more about the lark and owl chronotypes.

Brain Activity & Muscle Force in Morning and Evening Types

A new study measured changes in brain activity and muscle force from morning to night in morning and evening types.

The study involved 18 people. Nine were “evening types” who prefer to stay up late at night and sleep late in the morning; nine were “morning types” who prefer to go to bed early and wake up early. Data were collected four times in one day: at 9 a.m., 1 p.m., 5 p.m. and 9 p.m.



Results show a difference in brain activity between the two groups. In morning types their “cortical excitability” was highest at 9 a.m.; this level decreased throughout the day. The brain activity of evening types was highest at 9 p.m.

The study also tested reflex response and maximum muscle force. Reflex response was tested using spinal-cord stimulation; muscle force was measured by maximum contractions of the calf muscle.

Evening types became physically stronger during the day. Their reflex response improved and their muscle torque increased.

For morning types the results were mixed. Their reflex response improved throughout the day; but there was no change in the muscle force that they generated.

"We are suggesting that morning people may never reach their true maximum performance,” study co-author Dave Collins said in a University of Alberta article. “Their brain [activity] is going one way and their spinal cord activity is going the other, so it's offsetting. In evening people, both brain and spinal cord are at maximum in the evening, and they get maximum performance at night."

The authors suggest that these results may have implications for people who perform shift work.

Another recent study found that both morning and evening types performed well when tested 1.5 hours after waking. But the evening types pulled ahead when both groups were tested after being awake for 10.5 hours. They were more alert and had faster reaction times.

Learn more about chronotypes on the Sleep Education Blog.

Risk of Depression in “Evening Types” and “Morning Types”

A new study examines how chronotype may be related to depression. Is the risk of depression greater in “evening types” (“night owls”) or “morning types” (“morning larks”)?

The study involved 200 healthy adults between the ages of 18 and 99 years. Results show that people who are “evening types” have a higher risk of severe depressive symptoms.

MSNBC reports that evening types went to bed around midnight; morning types went to bed around 11 p.m. and woke up about 40 minutes earlier. Total sleep time was about the same for the two groups.

The study was unable to show if sleep schedule causes depression. But it suggests that going to bed and waking up a little earlier could improve your mood.

Yet making a change may not be easy; your DNA has a strong influence on when you prefer to sleep.

Learn more about evening and morning chronotypes.

Morning Larks vs. Night Owls: A Circadian Alertness Advantage?

People who are larks function better in the morning. Night owls are more alert in the evening. But which “chronotype” enables people to function better over the length of a day?

A new study in Science takes a look. It involved 16 early morning risers and 15 night owls. They performed alertness tests in a brain scanner after following their normal sleep schedule.

Newsweek and Science report that both groups performed well when they took the test 1.5 hours after waking. But the night owls pulled ahead when both groups were tested after being awake for 10.5 hours. They were more alert and had faster reaction times. Overall their performance improved by about 6 percent.

So do night owls have a natural alertness advantage over morning larks? Not necessarily.

Health News points out that an advantage in the lab may not translate to the workplace. A person who is a “morning type” will be alert during the hours of a normal workday. But “evening types” may struggle to align their natural sleep-wake pattern with their work schedule.

How Children Affect a Mother’s Sleep-Wake Rhythm

Some women may have a natural tendency to be a “night owl.” But a new study shows that their sleep-wake rhythm may change after they have children.

The study involved 179 women. Some were mothers, some were pregnant, and some had no children.

Results show that women with children are more likely to be “morning types.” This means they would have a stronger tendency to go to bed early and wake up early.

The study found that mothers woke up about 1.5 hours earlier on weekends. Women with children also reported falling asleep faster than the other women.

Which group of women got the most sleep? The women who were pregnant had the longest average sleep duration.

Learn more about the many complex factors that can affect a woman’s sleep.

What’s Your Chronotype? Understanding the “Lark” and “Owl” Circadian Sleep Patterns

A New York Times column examines the factors that contribute to your preferred sleep schedule.

This is also called your “chronotype.” It turns out that your DNA has a strong influence on when you like to sleep.

Some people have a circadian clock that makes them “evening types.” These “owls” have a natural tendency to stay up late at night and sleep late in the morning. Children tend to become night owls as teens because of a shift in the timing of their circadian clocks.

Some night owls have delayed sleep phase disorder. This involves a struggle to conform to work or social demands. It can be difficult for them to function well during the day.

Other people are natural “morning types.” These “larks” prefer to go to bed early and wake up early. Adults often become larks as they get older.

Some larks have advanced sleep phase disorder. They fall asleep several hours before a normal bedtime. As a result, they also wake up hours earlier than most people wake in the morning.

So do larks have an advantage over owls? After all, it was Benjamin Franklin who said, “Early to bed and early to rise, makes a man healthy, wealthy, and wise.”

A study in 1998 put these words to the test. It found no evidence that larks were healthier, wealthier or wiser than owls.

Not everyone fits neatly into the categories of morning or evening types. Many people are somewhere in between the larks and the owls.

And many factors such as genetics and light exposure affect when you are sleepy and alert. A new study in the journal Sleep examined some other factors.

It involved 5,720 college students at two universities in Spain and Italy. Results show that females went to bed earlier and slept longer than males.

Nationality also had a significant effect on sleep patterns. On average the Spaniards went to bed and woke up later than the Italians.

The study even found a significant but small “season of birth” effect. Subjects born in spring and summer went to bed later than those who were born in fall and winter. A study in 1999 reported similar findings.

Image by Rachel