Vonny said:
My memory has got much worse since I started caring for mum
this may be the key.
When we care for someone who has dementia we - at least in my experience - have to get into their world to try and understand conversations, behaviours etc. We also try to empathise with them - I remember telling Jan "yes, I have problems remembering this or that" to reasssure her, and it is true - some things have always eluded me.
In doing this it is easy to temporarily find it difficult to return to our own world. It takes so much energy - the caring - that we may not have the ability to do so with any speed.
Depression can also be a factor.
The thing about memory is that it is based on refreshing.
[large computers use something similar - hierarchical storage, where less frequently used information is progressively backed off its 'short term memory' into slower, long term memory, and can end up with a human needing to go to a safe to retrieve a tape]
The more things we do at a time, the more worries we have, the more that the refreshing doesn't happen, so things become less memorable.
I found that misplacing keys etc was not really a problem as we all do that from time to time. Picking up keys and wondering 'what are these things used for?' would probably freak me out though...