Shift workers make up about 15 percent of the American workforce, which translates to 15 million people in fields including hospitality, law enforcement and medicine. We may all moan about our sleeping issues, but most of our woes don't compare to those of shift workers. Some clock in at jobs when everyone else is sleeping. Others, such as waitresses, keep odd hours to accommodate fluctuating schedules. Statistically, the paltry, irregular sleep that comes with shift work corresponds to higher-than-average rates of metabolic disease and mood disorders. And bleary-eyed workers are prone to making potentially costly mistakes on and off the job.
Given the impact of shift work on both personal and population health, scientists and doctors are committed to figuring out, in precise detail, what happens to the body and brain, and what those changes mean, when people don’t get the rest they need.
Consider epigenetics: The young field (many scotches are older than it), perched at the nexus of behavior and biology, explores how various environmental conditions, including diet, stress, exercise and, yes, sleep, change gene activity. Epigenetics can help explain, for example, why identical twins share the same DNA but develop different diseases.
In one recent epigenetics study, a research team lead by Jonathan Cedernaes at Uppsala University in Sweden found evidence that a single night of sleep loss can affect the function of circadian clock genes — which regulate tightly choreographed bodily processes — in specific types of tissue cells critical to metabolic health. The study is the first to show the epigenetic effects of pulling an all-nighter at the molecular level. Think of it this way: Scientists can see the effects of skipping sleep by looking at single genes inside stomach fat cells. That’s a far cry from saying “you look tired.”
As we learned in high school bio, the roughly 25 thousand genes we all have are different-sized strips of DNA. That DNA sequence, coiled tightly inside cells, is the biological blueprint with which we enter and leave the world. Environmental factors can’t retroactively change these genetic plans, but they can change what our bodies do with them. How? By triggering chemical processes that leave markers on DNA — it’s like tagging the genome with some organic-compound graffiti.
In the current sleep-loss study, the environmental stressor was sleep loss and the epigenetic process was methylation, which occurs when a chemical compound called a methyl group gloms onto a DNA strand, thereby turning active genes off or inactive genes on.
The working hypothesis? Sleep loss would trigger methylation, which would in turn “shut off” clock genes in two types of tissue critical to metabolic processes: stomach fat and skeletal muscle.
We know that animals eventually develop obesity and Type-2 diabetes when the clock genes in these two types of tissue cells have been turned off.
Why does this matter? Clock genes power the circadian machine, the physiological system that coordinates a range of bodily processes according to a (roughly) 24-hour sleep-and-wake schedule. From previous studies, we know that animals eventually develop obesity and Type-2 diabetes when the clock genes in these two types of tissue cells have been turned off (through purposeful genetic modification).
Since shift workers disproportionately suffer from metabolic disorders, Cedernaes and colleagues set out to see whether otherwise healthy men who stayed up all night (in a context intended to mimic shift workers’ sleeping experience) would show both altered clock gene function in their fat and muscle tissue, as well as develop greater insulin resistance, a hallmark feature of Type-2 diabetes.
Fifteen normal-weight men visited a lab twice for two-night stays. Both times, they slept normally the first night. The second night, however, was experimental: They slept for 8.5 hours during one session and stayed up all night during the other session. After the experimental nights, researchers biopsied and analyzed the two types of bodily tissue. After the biopsies, they gave participants sugar water, and tested changes in levels of insulin resistance before and after drinking.
Tissue analysis showed evidence of altered clock gene activity only after the night of no sleep.
In particular, researchers saw signs of methylation (that epigenetic process mentioned earlier) in the stomach fat cells. The muscle cells showed changes in gene transcription, which is different from methylation, but also points to an off-kilter circadian clock.
“We don’t really know why there are these tissue-dependent changes,” Cedernaes told Van Winkle’s, “but it could be that these tissues are responding differently to sleep loss, because of course they have different types of function, and different processes take place at night and during the day because the body anticipates different biological needs when awake and asleep.”
Additionally, participants exhibited more insulin resistance when they drank sugar water after their all-nighters. People with insulin resistance, the number-one predictor of Type-2 diabetes, require more insulin to stabilize blood sugar levels.
Together, the findings support the notion that skimping on sleep triggers epigenetic changes that throw off the clock genes responsible for regulating metabolic processes. It’s not known, however, if a few nights of solid rest could “reset” these genes to normal levels, or if the small changes are cumulative. This study, like other epigenetic research, emphasizes the degree to which habits inform health, whether you feel #blessed or snubbed by the genetic lottery.
So what about those shift workers?
"With shift work, you're active when you're not supposed to be," said Cedernaes. "And your sleep isn't as good during the day as it is during the night, and then you have to shift back quickly — when your body might still be adapted to sleeping at night. It all disrupts the homeostatic process. The body isn't supposed to be shifting processes so quickly."
But, for people who can't or don't want to opt out of the shift-work life, Cedernaes recommends taking measures that lessen the burden of alternating between different circadian rhythms. In particular, he suggests trying blue light therapy, staying active and avoiding heavy meals before bed.