People who sleep less than six hours a night could be putting their bodies at a serious disadvantage, according to a study by the Surrey Sleep Research Centre published in the Proceedings of the National Academy of Sciences.
The new research showed than a lack of shut eye disrupts more than 700 genes critical for good health. This includes those related to the immune system, metabolism, sleep and wake cycles and the body’s reaction to stress.
The findings are particularly relevant to Americans. A survey published in the United States in 2010 showed that almost 30 percent of people said they slept no more than six hours a night.
The research also adds to evidence showing the potential dangers of sleep deprivation. In previous studies, researchers noted that subjects who slept less than five hours each night had a 15 percent greater risk of death from all causes than those who received adequate rest.
To measure the importance of sleep, the team at the Surrey Sleep Research Centre recruited 14 men and 12 women, all healthy and between the ages of 23 and 31, to live at the sleep center twice for a total of 12 days. On one visit, they stayed in bed for 10 hours a night. On the other visit, they were allowed only six hours in bed. On both occasions, at the end of the week, subjects were kept awake for 39-41 hours.
Scientists used EEG sensors to gauge how much the subjects slept on average. On the 10-hour nights, the men and women slept an average of 8.5 hours. On the six-hour nights, subjects slept about 5 hours and 42 minutes.
A blood test from each patient at the end of their stays revealed the impact of sleep on gene activity. In people who slept longer, the activity of about 1,855 genes rose and fell over a 24-hour cycle. In the sleep deprived patients, however, about 400 genes stopped cycling entirely. The remaining genes cycled within a much smaller range.
The impact on genes related to metabolism could worsen conditions such as diabetes or obesity, while changes to genes such as those in control of the body’s inflammatory activity could affect heart disease. A lack of sleep also influenced the genes that control the body’s biological clock—a shift that could increase sleep disruption.
It is still unknown how long it takes for gene activity to return to normal after sleep deprivation, however scientists hope to investigate this question in future studies. In addition, although many genes were disrupted, scientists can’t tell whether these were harmless, short-term changes, a sign of the body adapting to sleep deprivation or truly dangerous to patients’ health.