[Symptoms] Can sleep apnea manifest itself mainly via cognitive symptoms and without fatigue ?

[NotNotLaosho]

I wasn't necessarily thinking of sleepiness but more of fatigue in general, but from what you tell me, I guess it's just as possible.
I have a kind of more or less constant lack of energy if that can indicate anything.

[Deborah K.]

I didn't notice that I was tired or sleepy or anything else before I went on a pap machine.  I had an episode of atrial fibrillation and the heart doctor said I needed to have a sleep study, as apnea can cause AFib.  So I had the study and found, to my great surprise,  that I have severe sleep apnea.  Have a sleep study and then you will know one way or the other.

[NotNotLaosho]

I see. In a way that makes me feel better. I really hope it's just the sleep apnea that's causing this. To tell you the truth, I'm afraid it's not that (or not just that) that's causing my symptoms.

[theredheadsaid]

the apnea can make your sleep quality bad = sleepy. 
BUT
The apnea can cause low oxygen, which your heart and circulatory system need to provide you energy, and without that, you will get fatigued. 
So, apnea is the upstream cause of fatigue.

[Psychotech]

Rather than asking for advice go for a polysomnography test everything will be clear if you have sleep apnea and what type of apnea you have, how low your oxygen is falling, all this questions will be answered then come here for advice then may be we'll be able to help you.