I have this, and have been on CPAP (continuous positive airway pressure) treatment for about a year.

I thought I just snored and didn't realise I was obstructing.I was not particulalry complaining of daytime sleepiness.

Now I would not be without it.

Correctly treated there should be NO daytime sleepiness, people can even return to LGV driving with annual medical (advice that the treatment is being used).

 That is also safety critical I would suggest.

The specialist can tell that you are using it as the machine  records the amount of hours it was used each night  and gives an average. (or at least that someone is using it! Theoretically you could force your partner to wear it to bump up you numbers!)

If the person concerned has not been referred to a sleep clinic and had treatment they should do so.

If it is not working they should be reviewed by specialist. 

If they are not complying with treatment and are therefore unable to do their, job that is another thing...

I remember this topic has been mentioned before  and one person said that  they had been stopped from driving pending treatment.

Is the person still driving?

Cheers

Diane