Published on June 20, 2007 at 8:14 AM
The researchers assessed 18 standard sleep parameters, including sleep duration, time to fall asleep, and the amount of time in each sleep stage (stages 1 through 4 and REM sleep). They found large individual differences in these sleep parameters, which showed up consistently across the eight nights with sleep—regardless of whether or not there had been sleep deprivation in the night before. This meant that the individual differences were not driven by circumstance, but were at least partially biologically determined. For deep sleep (stages 3 and 4) in particular, the individual differences were overwhelmingly biological in nature.
“In this group of healthy young adults, the wide variation in the duration and structure of their sleep was, to a large extent, biological in nature. The next logical step is to look for genes that may be responsible for these large individual differences,” Van Dongen said.
The physiological or functional significance of these sleep traits remains a mystery. The fact that all subjects were healthy, young adults and good sleepers seems to rule out any immediate clinical relevance of the differences among them. However, Van Dongen thinks that the sleep differences may be predictive of future clinical conditions.
“Recognition of trait individual differences in sleep may help to understand the increasing evidence for a functional link between sleep and health,” he said.