Some 20 million Americans sleep during the day and work at night. This schedule affects their body clock, making them vulnerable to a condition that is known as shift work disorder.

This can not only lead to heart disease, it can also worsen sleep apnea.

If you have a job that requires you to work irregular hours, here are some tips to keep it from disrupting your sleep:

• Avoid frequently rotating shifts.

• Avoid long commutes that could put you at risk for falling asleep while driving.

• Keep your workplace brightly lit. Your body’s circadian rhythm will respond to light by keeping you more awake.

• Limit caffeine. Drinking coffee and other caffeinated drinks throughout your shift is tempting, but you should restrict it to the earlier hours of the shift, or you may be unable to fall asleep when you get home.

• Follow a regular sleep-wake schedule if you can.

• Ask your family to limit calls and other noisy activities to allow you to sleep soundly during the daytime.

• Use blinds to shut out daylight while you sleep.