WASHINGTON >> President Joe Biden in recent weeks has started 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 indents from the mask were visible on the president’s face as he departed the White House.

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

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

While his history with the condition has long been disclosed, it didn’t come up during his most recent physical in February. When he was vice president, doctors noted Biden had an irregular heartbeat probably linked to apnea.

The 80-year-old president is running for reelection and is the oldest person ever to hold the nation’s highest office.

Roughly 30 million people in the U.S. are thought to have the condition, though only about 6 million are diagnosed with it, according to the American Medical Association. In people with the condition, throat and tongue muscles relax and block the airway during sleep, caused by obesity, aging or facial structure.

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