Sleep "Fog"
Thinking ability suffers immediately after awakening

January 17, 2006

How do you feel immediately after you wake up? Does it take time for you to think clearly? The grogginess you feel is called sleep inertia. Scientists have found that the thinking abilities of people immediately after they wake up are worse than their abilities when they are deprived of sleep for 26 hours.

Researchers at the University of Colorado (Boulder, CO) and Harvard Medical School (Boston, MA) had nine people (8 men, 1 woman; average age = 29.1 years) sleep about 8 hours each night for three weeks at home and then spend a fourth week in a sleep lab. On the last day in the sleep lab, the subjects were tested for their ability to add pairs of two-digit numbers for several times after they woke up (1, 21, 41, 61, 120 minutes, and then every 2 hours after awakening).

The subjects did more poorly immediately after waking up than they did at all other times. Test scores measured one minute after people woke up were only 65% of the best performance. Test scores immediately after awakening were even worse than those after 26 hours of sleep deprivation.

Short-term memory, counting skills and math ability are measured using the two-digit addition test. Students and adults use these abilities in many different situations. However, it is not known if people would have problems performing tasks that require movement, such as driving, immediately after they wake up. Also, doctors, soldiers, police officers and fire fighters must often make quick decisions after they wake up. Future experiments may show how decision making is affected immediately after awakening and may change the way such decisions are made.

References and further information:

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