Jason (not his real name) walked into my clinic and started telling me things that would have kept an audience wide awake.

However, he was struggling to stay awake himself as he said softly: "My boss is about to fire me.

"I was a model employee but now I cannot concentrate on my work. My memory has become bad, and twice I fell asleep at my desk in the middle of the afternoon."

Jason, who works in his company's finance department, continued: "Once, I was about to give a talk to a group but when the spotlight shone on me, everyone saw me snoring with my mouth open like a fish."

I looked at Jason carefully. He was well built with a good physique. He was clearly not overweight.

However, an examination of his airway provided the answer to his distress - "kissing tonsils".

This describes the presence of extremely enlarged tonsils that touch each other across the mid-line of the throat. It results in an obstructed airway during sleep, with reduced oxygen going to the body.

What Jason now has is a medical condition called obstructive sleep apnoea.

During sleep, the obstruction can cause the oxygen intake to drop to a dangerously low level. The body reacts by increasing chest and body movements in an effort to suck more air into the body.

The individual's bed partner may be awakened by cycles of loud snoring or gasping noises followed by a long period of silence. Meanwhile, the chest keeps heaving.