You've listed all the symptoms of sleep apnea, including your age.
You keep waking-up because you have stopped breathing and eventually wake yourself self up, -which is better than having a stroke.
And yes, it can lead to dementia.
Get tested by a sleep specialist immediately, and if recommended, buy a CPAP machine (usually covered by insurance).
Don't want to spend the money?
Do you think it's cheaper to have a stroke, heart attack, or dementia and need someone else to wipe your backside every time you soil yourself?