The hidden cost of the night shift and how to sleep

Among the waste products the system clears are proteins called amyloid and tau, which accumulate in the brains of people with Alzheimer’s disease. A single sleepless night can significantly increase the amount of amyloid in the fluid surrounding the brain. Do that over and over again, year after year, and the implications are dire.

A Swedish study conducted by researchers at the Karolinska Institute followed more than 13,000 shift workers, including night shift workers, for up to 41 years, and found that shift work in midlife was associated with a 36% higher risk of dementia – an increase the longer a person worked shifts.

Foster is careful not to skip the link. “You wouldn’t say poor sleep causes dementia, but if you’re vulnerable, it could be a risk factor.”

Mark’s data suggests it’s a possible link, but he cautions that it’s speculative at this stage and there could be many other factors at play.

“The sleep issue,” he says, “but the big vascular things — high blood pressure, smoking, diabetes. What’s not been mentioned yet is how much of the risk of Alzheimer’s comes from those — those are things we can do something about.”

There is also tentative but growing evidence that sleep disturbances increase the risk of heart disease. An analysis of 35 studies published last year found that reducing sleep to about 4.5 hours for three or more nights significantly boosted immune system activity. This is normally a good thing when it comes to fighting infection, but it causes inflammation in the body which, if persistent, is linked to heart disease.

Disrupted sleep increases the stress hormone cortisol, which promotes insulin resistance and predisposes the body to diabetes. Elevated cortisol levels further worsen sleep, locking workers into a self-reinforcing cycle. Add to that a sugar-laden snack that will keep some shift workers going overnight and create an extremely unhealthy cocktail.

As if that weren’t enough, the World Health Organization’s International Agency for Research on Cancer (IRC) has classified night shift work as “probably carcinogenic to humans,” citing data linking it to breast, prostate, colon, and colorectal cancers in the same risk group as red meat.

This may be because disruptions in the body’s circulatory system alter the timing of production of melatonin, a hormone thought to suppress tumors, as well as vitamin D depletion due to lack of daylight and chronic low-grade inflammation that disrupts sleep.