Individual Responses to Sleep Deprivation Vary Substantially

By Dr. Gregg D. Jacobs

Although sleep deprivation can have significant adverse effects on mood, alertness, and cognitive performance, the effects of sleep loss depend upon the person, how much sleep is lost, motivation, and the circumstances under which sleep loss take place.

Some individuals show a remarkable tolerance for sleep loss, particularly if the person is motivated to cope with sleep loss (examples would be dealing with a crisis, caring for a newborn, etc.) or if the sleep loss occurs under positive circumstances (excitement, a vacation, social event, etc.).

Sleep deprivation researchers have learned that there are substantial individual differences in sensitivity to the effects of sleep deprivation on performance: some people are severely affected while others show minimal effects.

A recent study published in the journal Sleep (27 (3), 2004, 423-433) demonstrates that there are trait-like differences in individuals' responses to sleep deprivation. The study, conducted by Dr. Hans Van Dongen and colleagues at the University of Pennsylvania, examined responses to sleep deprivation in individuals who normally sleep between 6.5 and 8.5 hours.

Half of these subjects were asked to restrict their sleep to 6 hours per day, or extend their sleep by spending 12 hours in bed per night, for one week prior to experiencing 36 hours of total sleep deprivation. During the 36 hours of sleep deprivation, subjects were exposed to cognitive tests every two hours to measure the effects of sleep deprivation on neurobehavioral functioning.

The researchers found that, although prior sleep history (e.g. sleeping less or more than usual) affected responses to sleep deprivation (those who slept less than usual experienced greater decrements in neurobehavioral performance during sleep deprivation), there was stronger evidence for trait like individual differences in response to sleep deprivation. Specifically, subjects differed markedly in their responses to sleep deprivation.

While some subjects showed significant impairment in neurobehavioral functioning after 36 hours of sleep deprivation, others showed minimal impairment. And because the sample of subjects used in this study was a homogenous group of young, healthy adults, the researchers believe that individual differences in response to sleep deprivation in a real-world population of heterogeneous adults would be even greater.

Despite the evidence that the effects of sleep deprivation vary widely between individuals, the researchers were not able to identify the causes of these differences. For example, the differences may be due to biological pathways such as sleep need, sleep architecture, or psychological variables. Although these markers of differential responses to sleep deprivation have yet to b identified, it is likely that they may be similar to stress, which entails a combination of biological, emotional, and cognitive variables.

The results of this study are important since they clearly demonstrate that the effects of sleep deprivation are not a "one size fits all" phenomenon. Just as sleep requirements vary significantly amongst individuals, so do the effects of sleep deprivation. The effects of sleep deprivation are dependent upon the person, the type of sleep loss (partial or total sleep loss) and for how long (a few days or weeks), whether recovery sleep is allowed to occur, motivation, and the circumstances under which sleep loss take place.