for the first week. However, by the end of the study (one to 7 weeks later), total daily sleep time decreased to about 8.5 hours. This implies that the students made up for previous chronic partial sleep deprivation on initial nights and approached their underlying maximum ability for normal sleep by the end of the experiment. Compared with measures made prior to the research-related increased time in bed, the increased sleep times were associated with improved subjective alertness and longer times required to fall asleep on daytime nap tests (such nap tests are an objective way of measuring sleepiness such that the less sleepy and individual is, the longer it will take him/her to fall asleep during the day when asked to do so). There was also a significant improvement in reaction (response) time, although, this finding could be due to practicing on the task during the experiment. The results of this research study suggest that college students can increase their sleep time but probably cannot make themselves into permanent long sleepers. Another study, analogous to the sleep restriction studies described earlier, included a condition where time in bed was increased from 8 to 9 hours. This increase did not result in significant changes in performance (12). To our knowledge, only one study has shown reduced performance after extended sleep (13) while several have shown improved alertness and mood, particularly in individuals who may have been chronically partially sleep deprived prior to the studies. The studies generally support the ability of normal young adults to sleep an hour or longer each night with slight improvement in alertness and performance.
Sleep Duration and Health Consequences
Several research studies have shown that sleep restriction to about 4 hours per night on 1 - 2 nights has significant effects on normal individuals. Studies have shown an increased heart rate and blood pressure(14), increased inflammation as measured by C-reactive protein (a marker of inflammation which can be measured in the blood and which has been proposed as a risk factor for coronary artery disease -(15), impaired glucose tolerance (which can be a prelude to