Ann,

Cognition problems in PD seem to appear because of real changes in the brain. SPECT scans and other scans show differences in PDers with cognition problems and those without them.

Lack of sleep sure doesn't help though. I sleep well. Perhaps it's my tricyclic antidepressant (doxepin) that helps. If I do awaken in the night, I fall asleep immediately.

My main cognition problem is a worsening of my short term memory, which I believe is caused by the artane I take, which reduces my acetylcholine.
The only time it bothers me is when I'm flipping through channels with my remote, and I forget what I was watching.