Study: Caffeine before bedtime offsets your internal clock

A study shows that drinking caffeine three hours before bedtime can delay your internal clock significantly.

A double espresso three hours before bedtime can induce a 40-minute time delay in your body's internal clock, making it harder to go to sleep on time and more challenging to wake up in the morning, scientists have shown for the first time.

The study led by the University of Colorado Boulder and the Medical Research Council's Laboratory of Molecular Biology in Cambridge, shows for the first time that evening caffeine delays the internal circadian clock that tells us when to get ready for sleep and when to prepare to wake up.

The research team showed the amount of caffeine in a double espresso or its equivalent three hours before bedtime induced a 40-minute phase delay in the roughly 24-hour human biological clock.

The study also showed for the first time how caffeine affects "cellular timekeeping" in the human body, said CU-Boulder Professor Kenneth Wright, who co-led the study.

"This is the first study to show that caffeine, the mostly widely used psychoactive drug in the world, has an influence on the human circadian clock," said Wright.

"It also provides new and exciting insights into the effects of caffeine on human physiology," he said.

For the study the team recruited five human subjects, three females and two males, who went though a double-blind, placebo-controlled 49-day protocol.

The subjects were tested under four conditions: low light and a placebo pill; low light and the equivalent of a 200-milligramme caffeine pill dependent on the subject's weight; bright light and a placebo pill; and bright light and the caffeine pill.

Saliva samples of each participant were tested periodically during the study for levels of the hormone melatonin, which is produced naturally by the pineal gland when directed to do so by the brain's "master clock."

The master clock is re-set by exposure to light and coordinates cellular clocks throughout the human body.

Melatonin levels in the blood increase to signal the onset of biological nighttime during each 24-hour period and decrease at the start of biological daytime, said Wright.

Those who took the caffeine pill under low-light conditions were found to have a roughly 40-minute delay in their nightly circadian rhythm compared to those who took the placebo pill under low light conditions, said Wright.

The magnitude of delay from the caffeine dose was about half that of the delay induced in test subjects by a three-hour exposure to bright, overhead light that began at each person's normal bedtime.

The study also showed that bright light alone and bright light combined with caffeine induced circadian phase delays in the test subjects of about 85 minutes and 105 minutes respectively.

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Differences in sleep issues between women and men

This article explains the differences in sleep issues faced by women and men.

As a nation we are severely sleep-deprived. According to data from the Centers for Disease Control and Prevention, as much as a third of all Americans do not get the recommended seven hours of sleep a night.

"One of the myths is that we can power through or sleep when we're dead," Dr. Charles Czeisler, chair of the National Sleep Foundation and director of sleep medicine at Harvard Medical School, told "CBS This Morning." "But of coursewe'll get there faster if we don't get enough sleep. "

Women and men run into different roadblocks when it comes to their quest for a good night's sleep.

Women are more likely to toss and turn frequently and fight bouts of insomnia, a result of differences in hormonal regulation. Estrogen tends to shorten the length of the sleep cycle, which is why women often report that they experience sleep troubles around the time of menstruation, pregnancy or menopause.

According to a poll taken by the National Sleep Foundation, 63 percent of women versus 54 percent of men experience insomnia at least few nights a week. Women are also more likely to experience daytime sleepiness.

"One of the things is the internal clock controls the timing of sleep," said Czeisler. "It runs faster in women than it does men. It's only about a tenth of an hour but it adds up so that women, in general, their internal clocks are set to about an hour or an hour and half earlier than men, and that means it wakes them up earlier in the morning and it's harder to stay awake in the evening."

On the other hand, anatomical differences in men mean they're more likely to have sleep apnea -- a result of more fat deposit around the neck. Approximately 17 percent of men and 9 percent of women are diagnosed with sleep apnea, a type of sleep disorder that is caused by infrequent or paused breathing.

"If you crowd out the airway then you're going to have trouble when you sleep," said Czeisler. "One out of 3 men and about 1 out of 6 women suffer from disturbed sleep disordered breathing. But unfortunately, because it tends to be viewed as a male dominated disease women are much less likely to be diagnosed. Only 1 out of 10 women compared with men get diagnosed for sleep apnea."

Regardless of these challenges, everyone can take a number of measures to avoid sleep deprivation. Czeisler says good sleep hygiene is essential, such as going to bed at the same time each night to regulate your circadian rhythm. Some people find it helpful to set an alarm for bedtime. Creating a bedroom that's conducive to sleeping is also essential: remove all electronics from the bedroom and keep your room cool and dark.

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Health consequences of sleep disorders

This article discusses the different health consequences of sleep disorders and issues with an internal clock.

Ulcers, hyperglycemia, diabetes, hypertension, gastric intestinal problems are not always caused by diet - they could be linked to a disrupted internal clock.

Working a job that requires shift-work or experiencing chronic jet lag disrupts your circadian rhythm. It results in countless consequences to your body that simply can’t be fixed by counting sheep.

“Stimulants such as caffeine can disrupt a patient’s circadian rhythm but also irregular sleep habits, jet lag, Delayed Sleep Phase Disorder, which is common in teenagers, Shift Work Sleep Disorder and Advanced Sleep Phase Disorder, which is common in older people,” says Dr. Baqhar Mohideen, the medical director of the Center for Sleep Medicine at Porter Regional Hospital.

“A quarter of American workers are on shift-work – 10 percent of which experience Shift Work Sleep Disorders.”

Delayed Sleep Phase Disorder is when patients fall asleep late and have difficulty waking up in the morning. Shift Work Sleep Disorder affects patients who work nights or rotating shifts. Advanced Sleep Phase Disorder is when patients go to bed early in the evening but wake up very early in the morning around 3 a.m., for example.

Our bodies work on a 24-hour cycle called circadian rhythm or internal clock. The main function of our internal clock is to determine when we sleep and when we wake. Unfortunately if a circadian rhythm is disrupted it affects many biological conditions in the body such as digestion, the release of certain hormones, body temperature, etc.

“Because your hormones are all mixed up, there are lots of consequences – ulcers, chronic fatigue, insulin resistance, glucose intolerance, diabetes, etc.” says Mohideen, who is a Diplomat of the American Board of Sleep Medicine.

Glucose intolerance is an umbrella term for metabolic conditions which result in higher blood glucose levels known as hyperglycemia.

Dr. Muhammed Najjar, sleep specialist at the Franciscan Healthcare Sleep Disorders Center located in Munster, agrees there are consequences for a disrupted circadian rhythm caused by Shift Work Sleep Disorder.

“Daytime functions shouldn’t be at night. When there’s a misalignment between the patient’s internal clock and the outside world, it’s not good for the body,” says Najjar. “Shift work causes stress to the body so blood pressure gets elevated, which is why this disorder can cause hypertension. Treating circadian rhythm disorders can help lower blood pressure.”

Najjar says besides patients experiencing the side effects of a disrupted circadian rhythm there are side effects to sleep deprivation also.

Sleep deprivation affects hormones as well which can lead to body weight and body mass index issues. Gastrointestinal tract problems can surface and it can also cause insulin sensitivity which can lead to diabetes. A patient’s body can also become resistant to treatment.

“Many patients are sleep deprived because when they do sleep, it’s not adequate sleep. This affects their level of alertness and they can become accident-prone,” says Najjar. “If a patient’s shift work schedule rotates, or they sleep with a different pattern on their days off, it’s like having continual jet lag —the circadian system never gets the chance to fully catch up.”

The process of adjusting the internal clock with cues from the environment is called entrainment. Light is a stimulant and can effectively re-align one’s circadian rhythm.

Mohideen says some patients take medication or melatonin to assist in the readjustment process.

Melatonin is a body clock hormone that chemically causes drowsiness and lowers the body temperature in preparation for sleep.

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Study: Genes link circadian clock to eating schedule

A study found that specific genes link a person's circadian clock to their eating schedule.

For most people, the urge to eat a meal or snack comes at a few, predictable times during the waking part of the day. But for those with a rare syndrome, hunger comes at unwanted hours, interrupts sleep and causes overeating.

Now, Salk scientists have discovered a pair of genes that normally keeps eating schedules in sync with daily sleep rhythms, and, when mutated, may play a role in so-called night eating syndrome. In mice with mutations in one of the genes, eating patterns are shifted, leading to unusual mealtimes and weight gain. The results were published in this month's Cell Reports.

"We really never expected that we would be able to decouple the sleep-wake cycle and the eating cycle, especially with a simple mutation," says senior study author Satchidananda Panda, an associate professor in Salk's Regulatory Biology Laboratory. "It opens up a whole lot of future questions about how these cycles are regulated."

More than a decade ago, researchers discovered that individuals with an inherited sleep disorder often carry a particular mutation in a protein called PER2. The mutation is in an area of the protein that can be phosphorylated -- the ability to bond with a phosphate chemical that changes the protein's function. Humans have three PER, or period, genes, all thought to play a role in the daily circadian clock and all containing the same phosphorylation spot.

The Salk scientists joined forces with a Chinese team led by Ying Xu of Nanjing University to test whether mutations in the equivalent area of PER1 would have the same effect as those in PER2 that caused the sleep disorder. So they bred mice to lack the mouse period genes, and added in a human PER1 or PER2 with a mutation in the phosphorylation site. As expected, mice with a mutated PER2 had sleep defects, dozing off earlier than usual. The same wasn't true for PER1 mutations though.

"In the mice without PER1, there was no obvious defect in their sleep-wake cycles," says Panda. "Instead, when we looked at their metabolism, we suddenly saw drastic changes."

Mice with the PER1 phosphorylation defects ate earlier than other mice -- causing them to wake up and snack before their sleep cycle was over -- and ate more food throughout their normal waking period. When the researchers looked at the molecular details of the PER1 protein, they found that the mutated PER1 led to lower protein levels during the sleeping period, higher levels during the waking period, and a faster degradation of protein whenever it was produced by cells.

Panda and his colleagues hypothesize that normally, PER1 and PER2 are kept synchronized since they have identical phosphorylation sites -- they are turned on and off at the same times, keeping sleep and eating cycles aligned. But a mutation in one of the genes could break this link, and cause off-cycle eating or sleeping.

"For a long time, people discounted night eating syndrome as not real," says Panda. "These results in mice suggest that it could actually be a genetic basis for the syndrome." The researchers haven't yet tested, however, whether any humans with night eating syndrome have mutations in PER1.

When Panda and Xu's team restricted access to food, providing it only at the mice's normal meal times, they found that even with a genetic mutation in PER1, mice could maintain a normal weight. Over a 10-week follow-up, these mice -- with a PER1 mutation but timed access to food -- showed no differences to control animals. This tells the researchers that the weight gain caused by PER1 is entirely caused by meal mistiming, not other metabolic defects.

Next, they hope to study exactly how PER1 controls appetite and eating behavior -- whether its molecular actions work through the liver, fat cells, brain or other organs.

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Children's internal clock could result in trouble sleeping

This article discusses how a child's internal clock, which regulates their natural melatonin levels, could result in the child fighting off sleep at bedtime.

"Just one more story, please?" ''I need a glass of water." ''Mom, I can't sleep!"

When youngsters continually struggle to fall asleep at night, new research suggests maybe their body clock doesn't match their bedtime.

That doesn't mean tots should be up at all hours.

"Just like nutrition and exercise, sleep is critical for good health," said sleep scientist Monique LeBourgeois of the University of Colorado, Boulder, who is leading the research.

The ultimate goal is to help reset a delayed sleep clock so that young children can settle down more easily, she said. Hint: It seems to have a lot to do with light.

We all have what's called a circadian rhythm, a master biological clock, that regulates when we become sleepy, and when we're more alert. Those patterns vary with age: It's the reason teenagers are notorious for late nights and difficult-to-wake mornings.

But how does that clock work in preschoolers, who need more sleep than older kids or adults? A first-of-its-kind study tracked 14 healthy youngsters for six days to begin finding out.

The children, ages 2½ to 3, wore activity monitors on their wrists to detect when they slept. Parents kept diaries about bedtime routines.

Then on the last afternoon, researchers visited each home, dimming lights and covering windows. Then, every 30 minutes for six hours leading up to the child's appointed bedtime, they also coaxed each tot to chew on some dental cotton to provide a sample of saliva.

The reason: To test for levels of a hormone named melatonin that is key to the sleep cycle and also sensitive to light. At some point every evening, people's melatonin levels surge and a while later, they begin to feel sleepy. Among adults who sleep well, that melatonin rise tends to happen about two hours before whatever is their chosen bedtime.

For preschoolers, the new study found that on average, the melatonin surge occurred around 7:40 p.m. The children tended to be tucked in around 8:10 p.m., and most were asleep 30 minutes later, LeBourgeois reported in the journal Mind, Brain and Education.

When melatonin rose earlier in the evening, tots who hit the sack around 8 fell asleep a bit faster. But when the melatonin surge was closer to bedtime, the youngsters were more likely to fuss or make curtain calls after lights-out.

Two children in the study actually were tucked in before their rise in melatonin ever occurred, and it took them up to an hour past bedtime to fall asleep, she said.

"We don't know what that sweet spot is yet," LeBourgeois said, but the data suggest bedtime is easiest if the melatonin surge occurred at least 30 minutes earlier.

The study reinforces what doctors have long suspected is one bedtime barrier, said Dr. Jyoti Krishna, a pediatric sleep expert at the Cleveland Clinic. Other factors can disrupt a child's sleep, too, such as noise, stress or anxiety, or disrupted home routines, he cautioned.

"But this paper reminds us that, hey, there is a time that the body is more ready to sleep than at other times," Krishna said.

The National Institutes of Health says preschoolers need 11 to 12 hours of sleep each day; some typically comes from an afternoon nap.

Parents don't have melatonin tests as a guide, so Krishna advises looking for cues when setting a bedtime — yawning, rubbing eyes — and then to adjust that bedtime as the child gets older.

"The melatonin onset and our body rhythms change," Krishna said. "You can't stick to what worked two years ago with this child, because this child is now a different child."

About 25 percent of young children experience some type of sleep difficulty, including trouble settling down at bedtime, LeBourgeois said. Harried parents aside, there's concern that early-in-life bedtime frustration might lead to more persistent sleep trouble.

"Listen to your child's physiology," she advised. Some steps that might help:

—Research shows that in adults, too much light in the evening delays the melatonin surge and subsequent sleepiness. While there's no data in young children yet, LeBourgeois says dimming the lights about an hour before bedtime makes sense.

—Avoid electronics near bedtime, because they generate a specific type of light that triggers wakefulness. LeBourgeois was horrified to hear one parent offer a sleepless youngster an iPad to play with as long as the child stayed in the bedroom.

—And make sure blackout shades aren't keeping your children from getting enough morning sunlight, she said. Light in the morning also is key to keeping the biological sleep clock on schedule.

Stay tuned: With funding from the National Institute of Mental Health, LeBourgeois has begun a larger study that will track sleep patterns of 40 2-year-olds until they're 5. She'll also measure their light exposure, and periodically record their brain waves during sleep, in a bid to better understand the influence of sleep patterns on children's development.

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