You may feel overwhelmingly sleepy quite suddenly at these times, shortly before bedtime or feel sleepy upon awakening. The good news is that some research suggests that the accumulated sleep debt can be worked down or "paid off."
Though scientists are still learning about the concept of basal sleep need, one thing sleep research certainly has shown is that sleeping too little can not only inhibit your productivity and ability to remember and consolidate information, but lack of sleep can also lead to serious health consequences and jeopardize your safety and the safety of individuals around you.
For example, short sleep duration is linked with:
According to researchers Michael H. Bonnet and Donna L. Arand, "There is strong evidence that sufficient shortening or disturbance of the sleep process compromises mood, performance and alertness and can result in injury or death. In this light, the most common-sense 'do no injury' medical advice would be to avoid sleep deprivation."
On the other hand, some research has found that long sleep durations (nine hours or more) are also associated with increased morbidity (illness, accidents) and mortality (death). Researchers describe this relationship as a "U-shaped" curve (see illustration) where both sleeping too little and sleeping too much may put you at risk. This research found that variables such as low socioeconomic status and depression were significantly associated with long sleep. Some researchers argue that these other variables might be the cause of the longer sleep: the fact that individuals with low socioeconomic status are more likely to have undiagnosed illnesses because of poor medical care explains the relationship between low socioeconomic status, long sleep and morbidity/mortality. Researchers caution that there is not a definitive conclusion that getting more than nine hours of sleep per night is consistently linked with health problems and/or mortality in adults, while short sleep has been linked to both these consequences in numerous studies.
"Currently, there is no strong evidence that sleeping too much has detrimental health consequences, or even evidence that our bodies will allow us to sleep much beyond what is required," says Kristen L. Knutson, PhD, Department of Health Studies, University of Chicago. "There is laboratory evidence that short sleep durations of 4-5 hours have negative physiological and neurobehavioral consequences. We need similar laboratory and intervention studies to determine whether long sleep durations (if they can be obtained) result in physiological changes that could lead to disease before we make any recommendations against sleep extension."
But a key question is how much is too much or too little. Researchers Shawn Youngstedt and Daniel Kripke reviewed two surveys of more than 1 million adults conducted by the American Cancer Society and found that the