Shift Work: How to Protect Your Health When Working Nights

The central body clock, located in the suprachiasmatic nucleus of the hypothalamus, is synchronized mainly by light exposure and, under natural conditions, sets the rhythm of melatonin secretion, cortisol, body temperature, and appetite on a cycle close to 24 hours. Night work forces activity and meals into hours when the body — following the light signal and the internal clock — is physiologically primed for sleep and metabolic rest, while daytime sleep happens against the natural peak of wakefulness.

The problem is compounded by the fact that, besides the central clock in the brain, nearly every tissue and organ — liver, pancreas, fat tissue, muscle — has its own peripheral molecular clock, partly synchronized by the central clock and partly by meal timing and physical activity. Shift work leads to a situation where the central clock (responding mainly to light) and the peripheral clocks (responding partly to meal timing) start operating independently of one another — a phenomenon called internal desynchronization. It's this desynchronization, rather than sleep loss alone, that's considered the key mechanism linking shift work to metabolic disturbances.

A 23% increase in heart attack risk may look modest at the individual level, but at the population scale — given how large a share of the global workforce does shift work — it translates into a meaningful number of additional cardiovascular events each year. That's one reason the topic is treated as a public health issue rather than purely an individual occupational inconvenience.

In 2019, the International Agency for Research on Cancer (IARC), part of the World Health Organization, updated its classification of night shift work in Monograph Volume 124, keeping it in Group 2A — agents probably carcinogenic to humans. That's the same category as, among other things, consuming excessive processed red meat or very hot beverages.

Melatonin is the most commonly mentioned intervention for shift work, but — as we show in our separate article on the topic — its documented effect is real yet modest (extending sleep by a matter of minutes, in low-quality evidence). Below are strategies with a broader scope of action and independent support in the literature.

For many people, shift work is an economic necessity, not a choice they can simply abandon after reading an article about its health risks. That's why we take a pragmatic approach: rather than focusing solely on the scale of the risk, we try to point to concrete, evidence-based strategies — managing light exposure, strategic napping, and a consistent meal and sleep schedule — that meaningfully reduce part of that risk, even when the shift schedule itself can't be avoided.

Melatonin, covered in more depth in our related article, remains one option, but not the only one or the most thoroughly studied. Combining several strategies at once — rather than relying on a single intervention — has the strongest support in the available data.