My Dad is 86 and I've noticed he is having trouble keeping his eyes open. His Mom lived to be 109 (that's not a typo). She had surgery at 86 and never really was "right" again. She had trouble opening her eyes that got progressively worse until she passed. What causes this? Is this dementia coming on? He seems to be getting sun down dementia, maybe? Falling asleep at the table and seems disoriented later in the day/evening.
Sometimes medicine can make a person feel very sleepy. My blood pressure pills did that to me until I had the pills adjusted. Anti-histamines will also do that, along with pills that help calm a person down.
Wow, your grandmother had lived to be 109, that was amazing.