The hidden cost of the night shift and how to sleep it off
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 measurably raises amyloid levels in the fluid surrounding the brain. If you do this over and over again, year after year, the results will be annoying.
A Swedish study by researchers at the Karolinska Institute that followed more than 13,000 shift workers, including those who worked the night shift, for up to 41 years found that shift work in middle age was associated with a 36% higher risk of dementia.
Foster is careful not to exaggerate the connection. “You can’t say that poor sleep causes dementia,” he says, “but if you’re vulnerable, it’s a potential risk factor.”
Markus’ data indicates a possible link, but he cautions that this is a hypothesis at this stage and many other factors are likely at play.
“Sleep is important,” he says, “but so are major vascular conditions like blood pressure, smoking, diabetes. It’s never mentioned how much of the Alzheimer’s risk comes from these; these are things we can actually do something about.”
There are also tentative but growing indications of how sleep disturbance may increase the risk of heart disease. An analysis of 35 studies published last year found that reducing sleep to about 4.5 hours over three or more nights significantly increased the activity of the body’s immune system. This is normally a good thing when activated to fight infection, but it also causes inflammation in the body and, if persistent, is associated with heart disease.
Disrupted sleep increases the stress hormone cortisol, which increases insulin resistance and pushes the body towards a diabetic state. Higher cortisol levels also worsen sleep, locking workers in a self-reinforcing cycle. Add to that the sugary snacks that cause some shift workers to work through the night, and you have a seriously unhealthy cocktail.
As if that wasn’t enough, the World Health Organization’s International Agency for Research on Cancer (IARC) has classified night shift work as “possibly carcinogenic to humans” and put it in the same risk group as red meat, citing evidence that it is linked to breast, prostate, colon and colorectal cancers.
This may be because disruption in the body’s circadian system alters the timing of production of melatonin, a hormone thought to have tumor-suppressing properties, as well as vitamin D depletion from lack of daylight and chronic low-level inflammation promoted by disrupted sleep.
