Some of the comments here are shocking and exhibit serious ignorance of causes of vascular dementia.
This is a type of dementia caused by lack of blood flow to the brain. It can happen following stroke, but in the absence of stroke, it is absolutely relevant that your dad sits on his rear end all day watching television and does nothing more challenging that emptying the dishwasher.
If he’s actually concerned and wants to do something about it, give him the information readily available online at reputable medical websites that lifestyle choices, including regular physical activity, can prevent or in his case slow the advance of this condition.
Does he smoke?
Does he have high BP?
Does he have metabolic disorder or prediabetes or diabetes?
All of these are risk factors for vascular dementia, as is advancing age.
I’m sure his balance issues contribute to his lack of activity - this is common in elders who develop fear of falling and subsequently sit all day which is terrible for brain health.
Depending on what his various health issues are, he should be able to increase his activity levels and slow the advance of the dementia. He needs to get off his rear for part of every hour of the waking day. He needs to get fit again and yes, it is absolutely possible at his age. Give him this link and a means to access it if they don’t already have a device to tap into YouTube:
https://www.bobandbrad.com/
He can start with chair exercises and work his way from there to regular walks with your mom. He *can* improve his health, *IF* he wants to.
~ elder caregiver