How important is timing of sleep?

I have no problem getting eight hours of sleep. Getting my sleep in the right hours is another matter altogether though. Often I don’t hit the sack before 4AM (and still lie awake for a considerable time) and lately I’ve been pondering if this could be the reason my training progress and mood leaves a lot to be desired. Could perhaps a delayed sleep cycle lead to permanently raised cortisol levels? I’m thinking normal night time sleep perhaps provides for some beneficial interaction between melatonin and cortisol which I’m missing? I’ve been searching the web for an answer but can’t find anything but heaps of information on Seasonal Affective Disorder, which I don’t think I suffer from as I feel the same in the (long dark Swedish) winter as in the summer. I’m convinced it’s a lot more healthy to sleep normal hours, but I’d like to know precisely WHY. It will be easier to change my habits then, I hope…

A good way to suffer from SAD is to sleep through much of the day to recover from the late nights. You need to start moving the sleep times back to a normal schedule. Any reason for the times or just habit? What time do you train? What about mineral supplements and training program? Maybe you’re suffering from CNS fatigue.

Public release date: 29-May-2003
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Contact: Michelle Brandt
Stanford University Medical Center

Stanford researchers identify best hours for shut-eye when sleep must be limited
STANFORD, Calif. - People getting a minimal amount of sleep do better if they go to bed early in the morning rather than late at night, suggests Stanford University Medical Center research. A recently published pilot study on the effects of sleep deprivation also found that individual tolerance of sleep restriction varies widely, yet study participants had a better overall adaptation to early morning sleep.
“The results were surprising,” said Christian Guilleminault, MD, professor of psychiatry and behavioral sciences at the School of Medicine and lead author of the paper that appears in the May issue of Sleep Medicine. “We had suspected that the more sleep-restricted the participants were, the sleepier they would be - regardless of when they went to bed. That’s not exactly what we found.”

It is well known that a cumulative reduction in nightly sleep results in decreased daytime functioning and a lower quality of life. Many factors contribute to the ways individuals tolerate sleep restriction, but the impact on the exact time that sleep took place on next-day behavior had not previously been studied.

“The fundamental question we wanted to answer focused on the time of sleep,” said Guilleminault. “If people can sleep for only a short period of time, what time should they sleep?”

The study involved eight men ranging in age from 18 to 25. The researchers monitored the participants’ sleep and collected baseline data as they slept for 8.5 hours for two nights. The men were then split into two groups: participants in one group slept from 10:30 p.m. to 2:30 a.m. for seven nights; the other group from 2:15 a.m. to 6:15 a.m.

The participants spent the week in the laboratory where researchers tracked their behavior and wakefulness through a series of tests, including the “maintenance of wakefulness” test, a series of daytime nap studies during which a participant is asked to stay awake and not fall asleep; memory tests; and a driving simulator. Blood tests were also done.

Not surprisingly, the researchers found that sleep restriction affected all participants. Results of the wakefulness tests taken the day after 8.5 hours of sleep differed greatly from results on the last day of sleep deprivation. But the results also differed between the two groups, showing that the timing of sleep may have an impact on daytime function.

The early morning sleep group’s score on the wakefulness test was significantly better than the late-night sleep group, indicating that early morning sleepers overall were more tolerant of sleep restriction. In addition, the researchers found that participants in the early morning sleep group had better rates of sleep efficiency (the percentage of time spent sleeping in the four-hour window) and sleep latency (the amount of time spent falling asleep).

Data from other tests is still being evaluated, but Guilleminault said these preliminary findings warrant further studies of sleep placement. Such studies could have particular importance to members of the military or other professions where sleep restriction is common, he said.

Aside from the impact of sleep placement, Guilleminault said the most striking part of the study was the great difference in individual responses to sleep deprivation. He noted that one participant in the early morning sleep group was not impacted by sleep deprivation until the sixth day of the study; he functioned in a “borderline normal” way for the first five days. Another participant, this one in the late-night sleep group, reacted so poorly to his new schedule that he developed severe insomnia.

Guilleminault said the unpredictability of a person’s response to sleep deprivation is a good reason for people to be cautious about limiting their amount of sleep. “What we show is that everyone becomes impaired by sleep deprivation, and that abnormal responses will be triggered in some people,” he said. “Many people stay up all night to study for a final or to finish a big project for the boss, but this sleep restriction can be very detrimental.”

Among the researchers’ other findings was that the secretion of leptin, a hormone that regulates appetite, decreased significantly during the period of sleep deprivation. Decreases in leptin levels are associated with increased appetite and possibly weight gain, and Guilleminault said further studies should focus on a possible link between sleep deprivation and obesity.

Guilleminault’s Stanford collaborators on this study include Nelson Powell, MD; Sandra Martinez, MD; Clete Kushida, MD, PhD; Luciana Palombini, MD; and Pierre Philip, MD. Tifenn Raffray, MD, now at Paris University’s medical school, also contributed. The study was funded by the Sleep Education and Research Foundation of Palo Alto.

Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children’s Hospital at Stanford. For more information, please visit the Web site of the medical center’s Office of Communication & Public Affairs at

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Well, it’s almost 3 AM here now, so I really shouldn’t be in front of the computer writing this :smiley:

Just a quick note though… Thanks a lot for your reply Charlie. I guess you’re right - by sleeping through the day I get less sun light and that’s what causes SAD if I’m not mistaken. I’ll just have to break my habit. The reason for the habit is basically that I feel so good in the evening. I feel alert, enthusiastic and creative but just the opposite in the “mornings”. This has more or less always been the case, but lately it has gotten worse as my present work allows for very flexible hours. Unfortunately I seem to need some outer discipline - like school…

Thanks to you too Herb. Odd results really :confused:

I’m off to bed now anyhow. Good Night to the both of you!