What is considered "adequate sleep"?
Researchers are not in agreement as to what "adequate sleep" means. What we like to think about it as the amount of sleep that will make you function at your best, and will make you feel physically and mentally at your best.
There is no set amount of sleep that everyone needs, though three independent studies have found that young adults, on average, need about eight hours and 15 minutes a night.
What is the definition of sleep loss?
I think sleep loss is best defined individually in relation to what the person's sleep need is. We often ask the volunteers at the sleep lab how much would they like to sleep and how much sleep they obtain. That, in a way, could be a measure of sleep loss.
A more scientific measure would be to clearly define for a given person the amount of sleep that that person can achieve, their sleep capacity. And then define sleep loss as the difference between the sleep achieved in daily life and the sleep capacity of the person.
The first symptoms of sleep loss are decreased alertness, decreased attention, often a little bit of depressed mood.
Does sleep loss accumulate over time?
The current concept is that sleep loss definitely accumulates. With consecutive days of having too little sleep, you get worse and worse. Your sleep debt increases and your sleepiness increases, your alertness decreases and your performance decreases as well.
