Untreated sleep apnea has been proven to cause or worsen heart disease—and according to a new study, it happens faster than previously thought.

Researchers at the University of British Columbia-Okanagan Campus found that a single bought of sleep apnea impacts the human body’s ability to regulate blood pressure. Just six hours of the fluctuating oxygen levels associated with sleep apnea can begin to deteriorate a person’s circulatory system.

"While it is well established that sleep apnea is linked to high blood pressure, our study shows this condition has an impact on the cardiovascular system that can begin within a single day," Glen Foster, an assistant professor of health and exercise science, said. "After just six hours of fluctuating oxygen levels, similar to what happens with sleep apnea, the body's ability to regulate blood pressure is impaired."

Foster and his team observed the impact of intermittent hypoxia on the cardiovascular system in 10 healthy young adults. Participants wore a ventilating mask for six hours and oxygen levels were altered to mimic sleep apnea symptoms.

The findings showed that during that time period, reduced oxygen levels compromised the function of the participants’ baroreceptors and damaged blood flow to the legs. Overtime, this could impact vascular health.

"These findings suggest that interventions for people suffering sleep apnea should occur as soon as the condition is diagnosed," Foster said.

More than 18 million Americans suffer from sleep apnea.