It turns out that chronic sleep deprivation — in this experiment, less than six hours a night for a week — changes the activity of about 700 genes, which is roughly 3 percent of all we carry.
About one-third of the affected genes are ramped up when we go with insufficient sleep night after night. The other two-thirds are partially suppressed. Hundreds of “circadian genes” whose activity rises and falls each day abruptly lose their rhythm.
Among the genes disturbed by sleep deprivation are ones involved in metabolism, immunity, inflammation, hormone response, the expression of other genes and the organization of material called chromatin on chromosomes. These changes may help explain how inadequate sleep alters attention and thinking and raises the risk for illnesses such as diabetes and coronary heart disease.
“The findings will identify some of the pathways linking insufficient sleep and negative health outcomes,” said Derk-Jan Dijk, a physiologist at the University of Surrey in England, who led the study. “But how these things ultimately lead to obesity or diabetes is an unanswered question at this moment in time.”
The experiment’s results are “consistent with what we know from animal studies,” said James Krueger, a sleep researcher at Washington State University. “But until you do it in a human, you don’t know. We now have a survey of what genes are affected in humans by chronic sleep loss.”
Effects of sleeplessness
What’s clear is that inadequate sleep is a big problem.
In the federal government’s periodic National Health and Nutrition Examination Survey (NHANES), 37 percent of adults in 2008 reported “inadequate sleep” and 29 percent “severe sleep deprivation.” In a different survey in 2010, about 30 percent of employed adults reported sleeping six hours or less each day. Among night-shift workers, the prevalence of “short sleep” was 44 percent — and in those in warehousing and transportation, it was 70 percent.
A two-decade study of Wisconsin parents published last month found that 41 percent of parents of children younger than 18 slept for less than seven hours each night, and eight percent less than six hours. Only 31 percent of American high school students sleep eight hours on an average school night.
Sleeplessness has big consequences, too. The biggest is that it makes people . . . sleepy.
“We have looked at the behavioral response to this kind of manipulation [sleep deprivation] in great detail,” Dijk said. “Sustained attention, reaction time, working memory — we see effects on all of them.”
Cognitive performance, however, is just the most predictable and immediate problem. Others are rare or take years to develop.
Short duration of sleep is associated with a higher risk of developing heart disease and stroke. People sleeping less than six hours a day are twice as likely to have Type 2 diabetes as people sleeping eight hours. Dozens of studies across many countries have found a relationship between short sleep duration and obesity.