In a perfect world, I would go to sleep at night when tired and wake up after about eight hours of refreshing sleep at a time dictated by my internal body clock. But this rarely happens. Between my older daughter's swim team practices that begin before dawn and my younger daughter's gymnastics practices that run well past my ideal bedtime, I'm often torn (like many parents) between late nights and early mornings.
If we happen to get one day on the weekend that neither of them has practice or a meet, our alarm clocks are turned off and we all blissfully sleep in as long as we want. But research shows that by catching up on sleep on the weekends, I may actually be inducing a form of "social jet lag" that leaves me susceptible to a slew of chronic illnesses.
Till Roenneberg, a chronobiologist at the Institute of Medical Psychology at Ludwig-Maximilian University in Munich, Germany, coined the term social jet lag in 2006 to describe the effect that drastic changes in sleep patterns can have on the body. Roenneberg noticed many adults tend to sleep in on weekends to compensate for poor sleep during the week or to accommodate late nights of socializing over the weekend.
These adults think they're being healthy by catching up on sleep when they can, but Roenneberg found that changes in sleep patterns actually disturb body systems that rely on a circadian rhythm, such as temperature regulation, cell repair and digestion.
The science to back it up
A study conducted by Duke University Medical Center and published in the journal Scientific Reports analyzed the sleep patterns of almost 2,000 participants between the ages of 54 and 93 to determine if social jet lag would affect their health. Researchers found that those who slept irregular hours on the weekends were more likely to suffer from higher blood sugar levels, body mass index, blood pressure and more likely to suffer a stroke or heart attack.
However, the study's authors note that their findings don't show causality. "We can't conclude that sleep irregularity results in health risks, or whether health conditions affect sleep. Perhaps all of these things are impacting each other," said Dr. Jessica Lunsford-Avery, assistant professor in psychiatry and behavioral sciences from the Duke University Medical Center, in the study.
"Perhaps there's something about obesity that disrupts sleep regularity," Lunsford-Avery said. "Or, as some research suggests, perhaps poor sleep interferes with the body's metabolism, which can lead to weight gain, and it's a vicious cycle."
These findings further expound on previous studies that irregular sleep patterns could be linked to obesity and other health issues.
A study published in JAMA Pediatrics found that teens who experience social jet lag with major differences between their weekday and weekend sleep schedules are more likely to be overweight. The connection is particularly stronger for girls than for boys, the researchers found, although they aren't sure why.
In an earlier study published in Current Biology, researchers found that social jet lag was directly associated with increased body mass index, a key marker in diagnosing obesity. Additional studies have found similar links between changes in sleep patterns and chronic health conditions. A study published in JAMA Neurology found that older adults who reported changes in sleep patterns also had increased accumulation of the beta-amyloid proteins, which are known precursors of Alzheimer’s disease. Another study by the American Academy of Sleep Medicine found that for every hour of social jet lag a person experiences, the likelihood of developing heart disease increases by 11%.
The link between circadian rhythm disruption and cancer led the World Health Organization to declare night shift work a probable human carcinogen. Researchers now think this risk might extend beyond the night shift to those whose sleep patterns are altered by social jet lag.
So what can you do to reduce your health risks? In a perfect world, sleep would get more respect. School administrators, employers and we as individuals would align activities around sleep patterns rather than trying to squeeze sleep into the cracks of our lives.
But because most of us don't want to change jobs, keep our kids out of school or avoid socializing with our friends, the best we can do is to keep our sleep schedules as consistent as possible — during the week and on weekends — so that our bodies have a chance to get in a rhythm.
Editor's note: This article has been updated with new information since it was originally published in March 2018.