How to keep one's focus during discussions and meetings

I noticed that I have more and more serious problems keeping focused, and despite my efforts to fix it the problem is just getting worse over time.

When I'm in a research-related discussion with someone, my mind easily wanders, and I won't be able to recall the last thing other person was saying so I have to politely ask them to repeat it. Usually this is because I'm still thinking about the last idea they mentioned instead of continuing to listen to them talk, but sometimes it's just as if my mind just turned off for the duration of a sentence of two.

At least when I'm talking to one person, I can always ask them to repeat what they said or ask them to slow down. But when it's a group discussion or a lecture/talk, this is not possible. When I was an undergraduate and attended lectures regularly, I didn't have this problem.

Am I alone with this problem, or do others encounter it too?

What strategies can one use to improve concentration and comprehension? How can I train myself to focus better?

I am very concerned about this problem as it affects my academic work and performance.