it is possible to accurately measure the amount of sllep a person needs each day. Assuming the human body needs enough sleep to be alert the next day, reserchers at the sleep disorder center at stanford university medical school developed the measurement called the multiple sleep latency test (MSLT). the MSLT determines a person's need for sleep based on how fast the person falls asleep when given the opportunity to nap (Carskadon,1989). for example, a day worker who slept for six hours at night would receive a series of nap 'test' opportunites at 10:00 am., noon, 2:00 pm.and 6:00p.m.Each nap opportunity took place in a dark, quiet room lasting upto 20 minutes. if the subject did not fall asleep during any of the nap opportunities, he or she would receive a score of 20, which indicates optiml alertness with six hours of daily sleep. if, in contrast the subject fell asleep in three to four minutes on average, this low score would indicate serious sleep deprivation: six hours of daily sleep would not be enough for that person to maintain day time allertness. patients with norcolepsy, a genetically induced sleep-wake dissorder, typically score within this low range . thus there are normative and pathological values for the test that reveal weather total sleep time is sufficient for daytime allertness.
the average U.S worker obtains seven to eighthours of sleep each night and scores between 10 and 15 on the test. indicating chronic mild sleepines. when night time sleeping increasing to nine hours, day time sleepiness virtually disapears.
Therefore, sleep researchers suggest that close to nine hours of sleep each night is optimal for the average U.S worker to acheive full daytime alertness. Of cource, most of us rarely afford the luxuarry of going to bed when we feel sleepy and waking up when we are refreshed.Most of us day wake up and go to sleep according to external schedules-- alarm clocks, televison shows, work schedules-- rather than the way their body feels.
The problem is even greater than for shiftworkers.sleep researchers at stanford documented that effects of mild sleep deprivation are cumulatine .Although one night of reduced sleep may not may not significantly impair allertness, the impact grows on each succeeding night. Thus, the sleep patterns of shiftworkers cause sleep deprivation to buildup. Work schedules should include frequent days off to prevent this buildup of chronic deprivation.