Sleeping in could be bad for your health – social jetlag may affect metabolism

If it hurt to get out of bed this morning, you may take some comfort from a new study that has found sleeping in may be bad for your health.

The study of 447 healthy shift workers set to explore the health effects of social jetlag – that is, the difference between our body’s natural clock and our social clock (when we have to wake up for work, for instance).

Unhealthy habit: When your natural body clock is misaligned with your social clock. Unhealthy habit: When your natural body clock is misaligned with your social clock. 

Social jetlag, in practice, is when we don’t have to go to work and sleep in the next morning to a time that is more in line with our body’s clock.

“The behaviour looks like if most people on a Friday evening fly from Paris to New York or Los Angeles to Tokyo and on Monday they fly back. Since this looks like almost a travel jetlag situation, we called it social jetlag,” according to Till Roenneberg, a professor at the Institute of Medical Psychology at the University of Munich.

Researchers already know that social jetlag increases a persons risk of obesity – in fact, for every hour of social jetlag, the risk of being overweight or obese increases by about 33 per cent.

“However, this is the first study to extend upon that work and show that even among healthy, working adults who experience a less extreme range of mismatches in their sleep schedule, social jetlag can contribute to metabolic problems,” said the lead author, Patricia M Wong, a graduate student at the University of Pittsburgh. 

“These metabolic changes can contribute to the development of obesity, diabetes and cardiovascular disease.”

To find out, participants wore wristbands that measured their movement and sleep patterns during the course of a week. They also answered questions about their sleep, diet and exercise habits.

The researchers found that the more people slept in on their days off, the more likely they were to have a poor cholesterol profiles, higher fasting insulin level, larger waist circumference, higher body-mass index and were more resistant to insulin than those who had less social jetlag.

It seems that our bodies become out of whack, the more our body’s natural rhythm is compromised.

“Our findings suggest that a misalignment of sleep timing is associated with metabolic risk factors that predispose to diabetes and atherosclerotic [hardened arteries] cardiovascular disease,” the authors said.

“It’s not clear yet that this is a long-term effect,” Wong added. “But we think of this as people having to sleep and work out of sync with their internal clock, and that having to be out of sync may be having these health effects.”