Lost Z’s Not Easily Recouped

July 30, 2010 at 12:51 pm Leave a comment

Lost Z’s Not Easily Recouped                                                               

Many individuals believe they can adapt to chronic sleep loss or that recovery requires only a single extended night’s sleep.  Yet, a recent study (see Uncovering Residual Effects of Chronic Sleep Loss on Human Performance published in the Science Translational Medicine January 2010), showed that sleep recovery is actually harder than we thought. 

 The study examined the effects of “sleep deficit” — the cumulative amount of lost sleep due to poor sleep habits, sickness, awakenings, etc., over three weeks of alternating staying awake for 33 hours and sleeping for 10 hours – – the equivalent of 5.6 hours per night.  

 According to the lead author of the study, Daniel A. Cohen, M.D.:

  • The brain literally keeps track of how long we’ve been asleep and awake — for weeks.
  • An extended nights’ sleep (10 hours in the study) can restore your performance from chronic sleep loss to normal during the first several hours of wakefulness, but you will peter out very quickly after that.   .
  • Those who pull an all-nighter after 2-3 weeks of chronic sleep loss will have reaction times comparable to those who are legally drunk within 18 hours of being awake.  
  • Circadian rhythms may make you think you are managing the effects of sleep loss better than you are because for most people, melatonin, the hormone that makes you sleepy is lowest between 3 p.m. and 7 p.m. 
  • Of particular concern to researches was that the circadian low or some call it the circadian “night”, when the sleep producing melatonin is the highest, (roughly between 3 a.m. and 7 a.m.) magnified the effects of sleep loss, markedly slowing down reaction time – an important consideration for those with overnight jobs.
  • It could take up to two of weeks of a normal sleep schedule before someone overcomes a long-term sleep deficit.  

The Sleep Foundation says that sleep needs vary depending on lifestyle factors such as health, work schedules and stress, but they offer the following “sleep needs spectrum” below.

How Much Sleep Do You Need? *                                            

Newborns  (0 – 2 months) 12 to 18 hours
Infants  (3 -11 months) 14 to 15 hours
Toddlers (1 – 3 years) 12 to 14 hours
Preschoolers  (3 – 5 years) 11 to 13 hours
School-age children (5 – 10 years) 10 to 11 hours
Teens  (10 – 17 years) 8.5 to 9.25 hours
Adults (18 years and over) 7 to 9 hours



*Source: National Sleep Foundation


Erin O’Donnel, Fortifying Winks: Lost Sleep is Hard to Find, Harvard Magazine, July/August 2010.

Daniel A. Cohen, Wei Wang, James K. Wyatt, Richard E. Kronauer, Derk-Jan Dijk, Charles A. Czeisler, and Elizabeth B. Klerman, Uncovering Residual Effects of Chronic Sleep Loss on Human Performance , Science Translational Medicine 2, 14ra3 (2010).

The National Sleep Foundation


Entry filed under: Health Advice. Tags: , , , , .

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