Delaying bedtime by just 90 minutes each night damages cells that line the blood vessels, supporting the hypothesis that poor sleep is linked to heart health, a study among women participants has revealed.

A mild chronic sleep deficit may heighten the risk of developing heart disease later in life.

Surveys of thousands of people have found that people who report mild but chronic sleep deficits have more heart disease later in life than people who get adequate sleep.

A new Columbia University study of women, published in the journal Scientific Reports, now shows what’s happening in the body during chronic mild sleep deprivation.

After just six weeks of shortened sleep, the study found, that the cells that line our blood vessels are flooded by damaging oxidants. And unlike well-rested cells, sleep-restricted cells fail to activate antioxidant responses to clear the destructive molecules.

The result: cells that are inflamed and dysfunctional, an early step in the development of cardiovascular disease.

“This is some of the first direct evidence to show that mild chronic sleep deficits cause heart disease,” says study leader Sanja Jelic, director of the Center for Sleep Medicine at Columbia.

The researchers screened nearly 1,000 women for the study, enrolling 35 healthy women who normally sleep seven to eight hours each night who could complete the 12-week study.

For six weeks the women slept according to their usual routine; for the other six weeks, they went to bed 1.5 hours later than usual. Each participant’s sleep was verified with wrist-worn sleep trackers.

“Many problems could be solved if people sleep at least seven to eight hours per night,” Jelic said.

“People who are young and healthy need to know that if they keep getting less sleep than that, they're aggravating their cardiovascular risk.”

Jelic’s team is now designing a study to see if bedtime variability impacts vascular cells in the same way as chronic, but regular, short sleep.