Question regarding raising concern to a family members dr

My dad (83) is showing signs of dementia and we are all very concerned. Really bad hygiene issues, agitation and irritability when he gets confused. Lashing out in angry episodes for seemingly no reason or trigger. He’s struggling to follow conversations and forgets important details. He is EXTREMELY defiant and anti doctor and always has been. He had a heart attack in the summer of 2023 and it was like pulling teeth getting him to take any medication or accept care at all. I also feel his current memory symptoms really presented themselves post heart attack. The heart attack was the first time he’d seen a doctor in years. We are unsure how to go about raising concern with his primary care doctor and what can really be done given his defiance. Does my mother have any standing in calling his doctor to express concern / can anything be done if my father isn’t aware and/or unwilling to admit he needs help? How do you all encourage family members to get a memory screening when they’re lucid enough to resist? It’s been really hard watching this unfold and we all feel helpless and stressed. Any info is appreciated. Thank you all.