Dh has always had the tendency to zone out e.g. when he loads the dishwasher and I say something to him, he seems unable to take in what I am saying and respond. When speaking with his family his voice sounds like he is not really focusing, kind of very softy softy but absent minded. He doesn't sound like this when speaking to colleagues on the phone etc.
He is unable to 'get' what I (or the children) want or need unless it is something he has done before. So for example, if I ask for help with my email software (he works in IT but is not a technician) he does not seem to be able to listen to my description of the problem but jumps to conclusions, cuts me off and tries to fix it without understanding what the actual problem is. The best way I can describe it is that he is unable to understand concepts or situations that are new because he does not pay attention to the information that is given to him to make sense of it.
It almost comes across as if he is not intelligent but he is highly intelligent and has graduated with a first in a scientific topic, many years ago.
It's like he resides in his headspace in is not able (willing?) to be present in the moment and consider information from a broader perspective.
He has been quite stressed due to having young children, work, moving house etc. He is kind and helpful but often seems 'not with it'. 
He doesn't converse in a manner that takes into account what the other person is saying and seems to have delayed thought processing and response time (hope that makes sense).
When I received a kit in preparation for a cancer test and got a bit emotional and teary as I was scared of the procedure, he looked dumbstruck and could not comment on it not in an empathic way nor in a more scientific pragmatic way, he just didn't say anything at all and looked disinterested and confused. He was not worried not could he understand why I was worried. Later on when I took time to explain he got it and was sorry but he doesn't seem to be able to promptly process information in real times and respond in some sort of way so stays quiet often. On the other hand he can blurt out some impulsive and sometimes tactless stuff.
His mother has recently passed away from dementia, which she developed when she was 58 or so. DH is 45. I have often wondered if he has some attention problems (ADD?) especially as ds1 also has problems focusing but is also highly intelligent. I have always wondered if his father has high functioning autism. He is a successful medical doctor but is absolutely unable to take into account his families needs (but empathises with his patients).
I don't know whether to post this in relationship or health but I know he loves me yet he is unable to engage in realtime with what I or the children talk about. He seems absent minded and disengaged but is around for all the practical stuff, helps around the house and garden, he is dedicated but cannot communicate with us.
Could this be burn out? (but he was similar before we had dc)
Could it be add or similar?
Could it be very early onset of dementia?
Or just personality?
Any advice or thought should be great. Thank you.