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.

Working nights might affect your health differently depending on things like your gender, when you naturally feel awake or sleepy, or how much money you make — but this study didn’t check any of those things, so we can’t fully explain why other studies have found different results.

People who used to work nights don’t seem to have more health problems like diabetes or heart disease risks later on than people who never worked nights—even when you account for their age and medicines they take.

People who work nights don’t seem to have worse health markers like weight, blood pressure, or blood sugar compared to similar people who only work days—so night shifts probably don’t mess up your metabolism, heart, or immune system in this group of Germans.

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.