I recently changed to an S9 APAP machine, having previously had a Goodknight 420 and have been monitoring the software readings as a result. Something has registered, of which I was never aware: The 'central apnoes' seem to be closely linked to blood sugar levels.
I've used the machine at various times of the day to look at the readouts.
As many with type 2 diabetes - age-related - know, blood sugar starts to rise about 4am and with me tends to peak with a very high level at around 8am.
The S9 software - amazingly - shows a completely corresponding increase in 'central apnoes' during this time, which can even be as often as every few minutes around 6-8am if I stay sleeping. On the other hand, during the period up to 4 am, when blood sugar is normally low, there are virtually no centrals.
Obstructive apnoes however, remain at normal intervals - ie. seldom - the whole of the time.
The tie-in between central apnoes and blood sugar is something I will discuss with the doc next time I'm there.