A new study at Yale takes a deeper dive into the importance of sleep.

Doctors say they found the amount of sleep you get can affect brain health later in life.

Doctors say a bad night's sleep can increase your risk of heart disease, obesity and depression.

Doctors at the Yale School of Medicine looked at brain images of nearly 40,000 healthy adults in the UK between the ages of 40-69 to understand how sleep may affect brain health.

Doctors say eight hours of sleep should be the goal for everyone.

A nine-year study at Yale found getting less than seven hours a night or nine or more hours of sleep can lead to silent brain injuries that could lead to stroke and dementia.

The study focused on the connections in the brain.

"These white matter hyperintensities are known to associate with future stroke, with future dementia, are known to be a marker of brain aging and are known to be a very important marker of what we call neurology small vessel disease," said Yale School of Medicine Dr. Santiago Clocchiatti-Tuozzo.

This is associated with hypertension.

"These were not people who had sleep apnea or insomnia. So indeed, in the primary analysis, some of the participants do have sleep apnea," said Clocchiatti-Tuozzo.

Even though the study removed people who had sleep apnea, doctors still saw a risk for stroke and dementia.

Yale doctors say they hope in future clinical trials their work can improve brain health in older age. They also want to study how genetics may affect sleep.

The study found the same results even after adjusting for other risk factors, like smoking and diabetes.