Here's the situation:
A (male) friend's dad (call him X, he's in his mid-fifties) usually wakes up in the first two hours after going to bed to do washroom business. Last night, X woke up and realized he forgot essentially the last (few) year or so, such as his son having graduated from university (though he remembers his son is in university, and where), and pretty much all associated events in the last year (and even some other things like how to turn on the computer). He kept asking questions like "What year is it? What day is it? What month is it?" and looking generally confused, but didn't appear to be too absent-minded (like sleepwalking, I'm told). That basically continued for about an hour or so, until he was persuaded to fall back asleep. This morning, X had no recollection of the event, and pretty much had his memory intact (though maybe his wife telling him about the incident made him a little anxious).

My question is, would this be early onset of Alzheimer's? Or regular sleepwalking? Or transient epileptic amnesia? Or something else? How should my friend proceed? This is the first time it's happened (to their knowledge).

Thanks.