Mom has spells where she feels air-headed. She can verbalize the problem but does not know why. Any suggestions?

Thanks for your thoughts and ideas. When this feeling happens, it last for several days, so it is unlikely that it is caused by BP (tho that does fluctuate and she is on meds) or food. If that were the case, then it would fluctuate throughout the day, but the feeling is steady for days at a time. She is not on any new meds, nor does it occur with medication changes. She does not show signs of a stroke during these periods.
I know she does not drink enough water, which can cause lightheadedness, too, but again, her water intake remains stable during these periods and when she feels normal.
I will definitely relay this information to her PCP, but that will likely just lead to another doctor, and frankly, they all just say it's part of the dementia. This just upsets her because she does not think she has dementia - just memory problems. At 91, maybe it is better to just leave it alone as it has been going on for years, now, just like some days she has the ability to remember things, and somedays not.

Crazy "disease."  Thanks for your input!

Beyond the medical issues which Eyerishlass addresses, food choices can be a factor, especially if they're high in sugar and processed foods. You mentioned that she eats and watches tv. What does her diet consist of?

Your mom's symptoms may be a side-effect of a medication she's taking. Is she on anything new?

It could also be blood-pressure especially if she's sitting a lot. Her BP may drop when she stands up. That would make her lightheaded.

Not knowing the state of her health, lightheadedness can also be caused by lack of oxygen to the brain.

Many things could be the culprit. Does your mom show any signs of stroke? Slurred speech? Unable to use one side of her body?

Contact her doctor to report her symptoms. None of us are doctors so we can't really say what's causing this in your mom. If she's on numerous medications maybe the pharmacist can tell you if one of her meds can be causing this sensation in your mom.