Difficult to work due to sleep apnea

One of my colleagues was suffering from sleep apnea problems. He was finding it difficult to breathe during his sleep. His sleep was getting disturbed due to this condition. He was also not able to concentrate on his work in office due to a lack of sleep. Since he was facing this situation for several months, and there was no improvement in his condition, we asked him to consult a doctor. So he approached the nearby clinic that day evening and told about his situation. The doctor examined him thoroughly and asked him to use a cpap mask while sleeping. He started using it, and after some days, he told us that he is getting better relief from this condition. We were also surprised to see him working smoothly in the office. Is there anyone who is finding it difficult to concentrate on your work due to sleep apnea? Do tell us the measures you adopted to overcome it.