DH qualified on application for an early dementia/Alzheimer study and medication. In person, however, he managed to ace the exam. Even though he has a severe family history of Alzheimer's with his mother and grandmother he insists he is fine, and many people remain in the beginning stages for several years, as did his mother. In hind-sight we realize his mother probably started sometime around the year she retired at 65, then slowly declined until the last five years of rapid change. Certainly no one desires to acknowledge the possibility that they are "slipping". DH knows there is medication to help delay the severity of the disease, but refuses to acknowledge any problems.
Is there a doctor friend that he trusts and likes? Could you talk to this person and have them talk to your husband and give you an opinion as to what they think? Then discuss this with your husbands doctor.
It does sound like he should not be driving and it most certainly sounds like he should not be practicing any longer.
This might be one of his biggest fears that if he is "officially" diagnosed his life as he knows it is over. He will no longer be a doctor, something that has defined his life. And I am sure in his years of practice he has see the worst of what happens, not just to the patient but to the family, and this is a heavy burden to carry.
We have a family member who was accepted into and participates yearly in an Alzheimer's study. She has Alzheimer's and it shows on her brain scans. Has your husband's brain been scanned??