Working irregular shifts messes up your body clock, which makes it harder to sleep well. Poor sleep raises a stress hormone called cortisol, which then makes your sleep and heart function even worse over time — raising your risk of heart problems.

People who work night shifts or irregular hours tend to have weird cortisol patterns—low in the morning and high at night—which seems to make their sleep worse. This might be because their body’s internal clock is out of sync with their work schedule.

Working irregular hours or not sleeping well can mess up your body’s internal clock, which in turn hurts your metabolism and liver — making it harder for your body to process food and stay healthy.

When your body's internal clock is out of sync—like from shift work or jet lag—it messes up your stress hormones, stops your sleep hormone from working right, and turns on inflammation in the same way that being tired or stressed for a long time does.

Nurses who work nights and have trouble sleeping are much more likely to develop heart problems, even when you account for their age, weight, and work hours—suggesting that just having insomnia might be a hidden danger for their hearts.