It seems brain atrophy is a part of getting older and not necessarily getting Alzheimers. My last MRI showed it too.
Also, if you're dehydrayded you're brain will show shrinkage...I guess it's like a sponge. LOL I better get that drink.
Possible causes of frontal lobe atrophy include brain injury, brain tumors. hydrocephalus (which can cause headaches and apathy), excess alcohol intake, various forms of dementia, etc. Conditions such as multiple sclerosis or CNS lupus can also cause cerebral atrophy.
I'm not a doctor and I'm not saying anything is wrong--but if I was told this and I was also starting to feel not as sharp as usual and somewhat apathetic, I would pursue it further and make sure something that's treatable isn't being missed.
You're only 63. You might want to ask the doctors, "How does my MRI compare to the MRIs of other 63-year-old patients you've seen?"
I would definitely make sure you're doing things you can to help maximize brain function--Eating omega-3-rich foods, blueberries, green tea, apples, etc.; regularly doing crossword puzzles or other word games, staying as physically active as you can (as your doctors allow), staying socially connected with family and friends, etc.