In my NAION post I mentioned sleep apnea as an important risk factor for ischemic nerve disease.
The exact connection between non-arteritic anterior ischemic optic neuropathy (NAION) and obstructive sleep apnea (OSA) is not fully understood, but there does seem to be a connection. Various studies have looked into a connection and found that among patients with NAION, anywhere from 30% up to 91% also had OSA. This is much higher than the general population.
I have heard multiple theories about how the two are connected:
1 OSA is generally bad for your circulation, so if you have OSA it is more likely for NAION to occur.
2 OSA causes drops of oxygen. If the blood does not have adequate oxygen then the nerve won't get what it needs to survive and that causes the NAION.
3 OSA causes changes in blood pressure. Apnea means you stop breathing. If there is a long pause in the breathing the body goes into a mini panic and the blood pressure shoots up momentarily, then finally when the patient takes a breath the blood pressure crashes back down. All of this happens while the patient is sleeping and so they are usually unaware.
I believe it is likely all three of those. You can imagine a scenario where a patient has poor circulation all the time, then during the night has an apnea and the blood pressure shoots up then goes back down- too low. Then just at the moment the blood pressure is crashing down the next apnea begins and the oxygen drops with it. All three of those conspire together and deprive the nerve of the blood supply and oxygen it needs.
Once NAION occurs, the nerve is swollen and damaged, and there may not be much that can be done. However, it could get worse, so it is important to identify any risk factors and treat them. That is especially true when we consider the possibility of an event in the other eye.
Treating the risk factors is my main recommendation.
One study looked at patients with NAION and moderate or severe sleep apnea. (Mild sleep apnea means the patient stops breathing more than 5 times per hour, moderate occurs more than 15 times per hour and severe occurs more than 30 times per hour.)
They looked at whether the patient used their CPAP machine and whether they had an event in the second eye. The patients who did not use CPAP were 25 times more likely to have the second eye event. In other words, patients on CPAP treatment were 25 times less likely to have that other eye event! We are often excited to see a treatment that reduced risk by 2 or 3 times. This was a real substantial reduction at 25 times.
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| CPAP can really reduce risk if a patient has moderate or severe OSA. |
In summary, we don't know for sure how OSA and NAION are connected but there is definitely some link between the two. If a patient with NAION does indeed have OSA then treatment with CPAP machine or other treatment options could substantially reduce their risk of new events.