The man, who was a life-long smoker and had chronic bronchitis, was admitted to King's Mill Hospital in Sutton in Ashfield, Nottinghamshire, because he was having hallucinations during the night and was confused during the day. Doctors could find nothing wrong with him, apart from the bronchitis and decided he had dementia after a brain scan showed mild atrophy. They were about to send him home when his wife mentioned he was a snorer.
His snoring was loud and included periods of choking and breath-holding - symptoms of a common disorder called sleep apnoea. Tissue at the back of the throat collapses and blocks the airway, which reduces oxygen levels in the blood.
In the man's case, the sleep apnoea combined with his bronchitis caused the oxygen level in his blood to fall very low during the night. Doctors arranged for him to have oxygen in bed through a mask and his hallucinations and confusion rapidly improved.