A physical examination of the mouth and throat can’t alone identify those whose snoring signals a more serious sleep-breathing problem, researchers said on Monday.

The only sure way to diagnose obstructive sleep apnea is with an overnight test that monitors a number of things, including airflow through the nose and mouth, snoring, oxygen saturation, certain electrical activity of the brain and body position, according to doctors at Ludwig-Maximilians-University in Munich, Germany.

The condition, afflicting up to 4 percent of the U.S. population, causes repeated interruptions in breathing, leading to daytime sleepiness and other health consequences.

In a study published in the February issue of the Archives of Otolaryngology - Head & Neck Surgery, the German researchers said they looked at 101 patients who complained that they were having snoring problems.

They were examined under one process, which included a medical history and a look at anatomy in their nose and throat, and again by overnight sleep tests.

The patients ultimately diagnosed with apnea by the overnight test had readings on the first physical tests that were not significantly different from those did not have apnea, the study found.

“None of the reported medical history and/or anatomical parameters alone or in combination could be used to distinguish patients with (apnea) from snoring patients,” the report said.

“In our opinion, all patients seeking treatment for snoring should be screened overnight using a device measuring at least oxygen saturation and airflow,” it added.

“If the results are suggestive of (apnea), or if patients complain of excessive daytime sleepiness, standard (overnight tests) should be applied,” it concluded.