I'm in my early forties, and I've been having the same worries you list the whole time.
And the answer (for me, so far) is....it's complicated.
I definitely think I have a harder time processing new ideas. OTOH, I have a lot more context to connect them to, so I feel like I end up with a better understanding when I DO get them. I also have a wider perspective to decide WHAT I want to spend my precious time learning. When I do learn something, I'm less likely to think it's the answer to everything, while I'm still able to get excited and enjoy how much easier this makes many of my tasks.
And it's really hard for me to say how much is REALLY having a harder time grasping new ideas, and how much is a mix of (1) that additional context, which makes it harder/longer before I feel the sense that I truly "get" it (2) the overwhelming sense of how many things I DON'T know that makes it feel like "I'm not learning like I used to".
Docker has been on my list to learn for ~4 years, even though I've used it indirectly for most of that time, for example, but it's not that I haven't been learning new concepts in that time - I've just not been able to find free time where Docker has been on the top of my list. Kubernetes shows up on HN, and I've not done more than googled the general idea. Are these omissions because I don't have the capability to learn as well, or because I've got a very full schedule and mental web of connections to fit them into? No way to be sure - I don't know of any way to quantify them.
I try to make sure that I end each week being able to say I learned something new, and while those bits are often small, they are also often significant in my day-to-day.
Also, don't discount the impacts of physical decay on the psychological. Being unable to sit comfortably for long stretches, the wear and tear of a million tiny aches - they may as much to blame for psychological limitations from age as any direct neurological degradation.
And the answer (for me, so far) is....it's complicated.
I definitely think I have a harder time processing new ideas. OTOH, I have a lot more context to connect them to, so I feel like I end up with a better understanding when I DO get them. I also have a wider perspective to decide WHAT I want to spend my precious time learning. When I do learn something, I'm less likely to think it's the answer to everything, while I'm still able to get excited and enjoy how much easier this makes many of my tasks.
And it's really hard for me to say how much is REALLY having a harder time grasping new ideas, and how much is a mix of (1) that additional context, which makes it harder/longer before I feel the sense that I truly "get" it (2) the overwhelming sense of how many things I DON'T know that makes it feel like "I'm not learning like I used to".
Docker has been on my list to learn for ~4 years, even though I've used it indirectly for most of that time, for example, but it's not that I haven't been learning new concepts in that time - I've just not been able to find free time where Docker has been on the top of my list. Kubernetes shows up on HN, and I've not done more than googled the general idea. Are these omissions because I don't have the capability to learn as well, or because I've got a very full schedule and mental web of connections to fit them into? No way to be sure - I don't know of any way to quantify them.
I try to make sure that I end each week being able to say I learned something new, and while those bits are often small, they are also often significant in my day-to-day.
Also, don't discount the impacts of physical decay on the psychological. Being unable to sit comfortably for long stretches, the wear and tear of a million tiny aches - they may as much to blame for psychological limitations from age as any direct neurological degradation.