WASHINGTON – President Joe Biden in recent weeks began using a continuous positive airway pressure, or CPAP, machine at night to help with sleep apnea, the White House said Wednesday. The revelation comes after the marks of the mask were visible on the president’s face as he left the White House.

The president has disclosed since 2008 a history of sleep apnea, a potentially serious but common condition in which breathing can stop and start overnight. Biden used the machine Tuesday night, White House officials said. The lines imprinted on his face were evident when he left Wednesday morning to give a speech in Chicago.

A CPAP machine is a motorized device that pumps air through a mask to open up a sleeper’s airway. About 5 million Americans have tried them.

While her history with the condition has long been revealed, it didn’t surface during her most recent physical in February. When he was vice president, doctors noticed that Biden had an irregular heartbeat likely related to apnea.

The 80-year-old president is running for re-election and is the oldest person to hold the highest office in the nation.

About 30 million people in the US are thought to have the condition, though only about 6 million are diagnosed with it, according to the American Medical Association. In people with this condition, the muscles of the throat and tongue relax and block the airway during sleep, due to obesity, aging, or facial structure.

They stop breathing, sometimes for as long as a minute and hundreds of times each night, then wake up with loud gasping and snoring. That prevents them from having a deep and restful sleep. Untreated sleep apnea can lead to dangerous sleepiness and an increased risk of heart attack. The problem is more common in men than in women.