It’s often thought that getting adequate sleep is the most important thing we can do for our health. And it makes sense, as skimping on zzz’s is linked to an increased risk of diabetes, obesity, heart disease, and decreased cognitive functioning. But the question is: Why?

A new study, led by researchers at Massachusetts General Hospital, gives us an answer to this very question. According to the study, which was published in the journal Nature, adequate sleep protects against health issues by reducing inflammation in the body that can cause disease.

The team, led by Filip Swirski, Ph.D., of the MGH Center for Systems Biology, tested how poor sleep affects atherosclerosis. Atherosclerosis, often the cause of cardiovascular disease, is a condition in which fats and cholesterol build up on your artery walls and can restrict blood flow. They found that the mice who constantly had their sleep disrupted had increased plaque buildup on their arteries and higher levels of inflammatory cells in their blood vessels.

The researchers also found that the increase in inflammatory cells was triggered by a decrease in the hormone hypocretin, which plays a vital role in regulating sleep and the production of white blood cells. The mice with less sleep had lower levels of hypocretin and increased levels of inflammatory white blood cells, which increased their risk of developing atherosclerosis.

“We have discovered that sleep helps to regulate the production in the bone marrow of inflammatory cells and the health of blood vessels and that, conversely, sleep disruption breaks down control of inflammatory cell production, leading to more inflammation and more heart disease,” said Swirski in a statement.

So how much sleep do you need to prevent cardiovascular disease and keep inflammation levels low? The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults sleep more than seven hours a night—although research shows that 35 percent of U.S. adults report sleeping less than seven hours a night.

On top of hours of sleep, you can also work to improve sleep quality. Some easy ways to improve your sleep quality and duration include making your room darker and lowering the temperature, removing electronics from your room, avoiding caffeine about 10 hours before you sleep, and cutting off overly stimulating activities at least an hour before bed.

The good news is that on top of helping to protect against cardiovascular disease, you may see some immediate benefits like more creativity, sharper attention, and less stress! With World Sleep Day, it’s the perfect time to turn our attention to our sleep hygiene and try out some of these tips.