New Sleep Research from the Human Chronobiology Lab

Napping and Cognition

	Research assistant being analyzed at the Human Chronobiology Laboratory.

Nappers concerned that a mid-day snooze might ruin a good night's sleep – fret not! Ongoing research from NewYork-Presbyterian Hospital/Weill Cornell Medical Center may show that not only does napping have little effect on sleep onset, but it may also be beneficial for mental processing the following day.

People over the age of 60 get two hours less sleep than younger individuals, which can impair mental functioning during the day. The researchers believe that a mid-day nap may improve daytime performance and mood in the elderly and in those who don’t get enough rest. The subjects are all "normal sleepers," but the researchers want to learn how napping affects their daily lives and mental functioning.

"By learning more about how normal people sleep, we may gain a better understanding of what is happening in the bodies and minds of those with sleep disorders," says Dr. Patricia Murphy, the associate director of the Human Chronobiology Laboratory at NewYork-Presbyterian/Weill Cornell. Along with the laboratory's director, Dr. Scott Campbell, she studies the influences on human sleep cycles, termed human chronobiology – research into the relationship between biology and time.

Participants in the study come to the sleep lab for several nights, where their sleep and wakefulness states are recorded via electrodes attached to the head and a wrist activity monitor. After napping, and on the following day, they are then asked to perform arithmetic, decision-making and reaction time tests.

During napping-days results have shown that subjects' cognitive performance is better right after the nap and the next day, and napping does not affect their nighttime sleep, when compared to non-nap-days.

Menopause and Sleep Maintenance

Last month, "Science Briefs" featured sleep research from Dr. Matthew Ebben, looking at how body temperature plays a role in sleep onset. Dr. Murphy is also studying, in women with menopausal "hot flashes," whether body temperature during sleep influences the ability to remain asleep and get back to sleep quickly after waking up.

Dr. Murphy's research is examining whether melatonin can help menopausal women who suffer from hot flashes sleep better throughout the night. Melatonin is a hormone secreted by the body during nighttime hours in response to darkness and is thought to influence sleep rhythms. It has also been known to lower body temperature.

The causes of hot flashes are unknown, but they are a common symptom of menopause, associated with, but not caused by, lowering levels of estrogen in the body. Dr. Murphy's study is examining the roles of other hormones, particularly luteinizing hormone – a hormone that triggers ovulation – in the regulation of temperature and sleep problems in menopausal and post-menopausal women.

Having Trouble Sleeping in Your Genes?

People who suffer from Delayed Sleep Phase Disorder can't fall asleep until the early morning hours and don’t wake up until the late afternoon. Advanced Sleep Phase Disorder is just the opposite – falling asleep early (around four or five in the afternoon) and waking up in the early morning hours. People who suffer with these sleep disorders find it impossible to break out of this cycle.

That is why Drs. Campbell and Murphy are researching a possible genetic link. The scientists believe that these unusual sleep cycles may be genetically determined.

Participants in the study remain at the sleep lab for three weeks. During their stay, participants are not allowed to look at clocks, view television, listen to the radio or read anything that may clue them into the time of day or date.

These measures control for environmental influences that may affect subjects' sleep patterns. The researchers want the subjects to live on their own internal clock, so that the scientists can accurately determine the lengths of their wake and sleep cycles, explains Dr. Murphy.

The researchers from the Human Chronobiology Laboratory are collaborating with scientists at Rockefeller University to help locate the genes that may be responsible for the study participants' sleep woes.

If you are interested in participating, please call Ms. Dawn Vega, research coordinator, at (914) 997-5825 for eligibility information.

For media inquiries please contact Andrew Klein at 212-821-0560 or ank2017@med.cornell.edu