In Sleep Deprived Pay the Price for Shift Work, we learn more about the risks to 20% of American workers that are night-shift workers. These are folks who work as police officers, security guards, truck drivers, hotel desk clerks and auditors, pilots, nurses, and more jobs than I can mention. We’ve known that this sort of shift work puts you at higher risk for accidents and stress, and since December, we’ve known that the World Health Organization actually considers it carcinogenic with health effects such as:

* Night-shift workers have a 40% to 50% increased risk of heart disease compared with day workers, various studies have found.

* People who get five hours of sleep, common among night-shift workers, are 50% more likely to be obese than normal sleepers, Columbia University researchers have found. Several dozen other studies have tied sleep loss to weight gain as well.

* Women night-shift workers have higher rates of miscarriage, pre-term birth and low birth-weight babies.

* Night-shift workers show increased rates of breast (by 50%) and colon (by 35%) cancer in numerous, independent studies. And animal studies have shown that exposure to dim light during the night-time can substantially increase tumor development.

But why would this be?

Among the most significant — and startling — reasons: As much as 15% of human genes function on a schedule, with highly regulated, oscillating patterns of activity.

These clocklike genes are common features of most cells and can be found in every major organ in the body. They, in turn, affect the schedule of scores of biological functions, from metabolism to cell division to cognitive processes.

Wow.