Most people know the feeling of dragging yourself out of bed in the morning and feeling wiped out periodically (or chronically) throughout the day. Many of us even have trouble falling asleep at night, as it seems harder and harder to put the cell phone down or turn off the computer.
Researchers have come up with a new term for our skewed sleep-wake cycles: Social jet lag. And it could be responsible for more health issues than just feeling tired from time to time.
People who were more socially jet lagged were more likely to have higher body mass indices (BMIs) than others.
Social jet lag refers to the fact that the schedules we keep are fundamentally out of sync with our internal clocks, which, along with the sun's movements, cue us to wake and sleep at certain times of the day.
"We have identified a syndrome in modern society that has not been recognized until recently," said study author Till Roenneberg in a news release. "It concerns an increasing discrepancy between the daily timing of the physiological clock and the social clock. As a result of this social jetlag, people are chronically sleep-deprived.” Sleep-deprivation itself has been linked to insulin resistance, heart disease, and earlier death.
When you sleep, as opposed to how much you sleep, may be the real key.
The authors of the new report looked at data over a 10-year period, and chronicled participants’ sleep schedules and certain body measures, like weight. They found that people who were more socially jet lagged were more likely to have higher body mass indices (BMIs) than others. What’s interesting is that the relationship between social jet lag and BMI was separate from sleep duration, suggesting that it really is whether our clocks are out of sync rather than how long we sleep that’s to blame.
Roenneberg also points out that social jet lag is a fairly recent development in human history. Humans’ schedules may have started shifting with the advent of the light bulb, but says, "[w]aking up with an alarm clock is a relatively new facet of our lives.” The results of the study may add substance to the idea that kids might be better off if school started a little later.
The study was carried out by researchers at the University of Munich, and published in Current Biology.