What Causes Memory Loss While Suffering From Elevated BP?

My husband is 67 years old and is having memory loss that is becoming noticeable. His judgment is being affected, he doesn t pay bills, etc. Last year he saw a neurologist and had a CT scan and MRI of the brain that were normal. He has high BP and our Family doctor recently increased his thyroid from 100 mg to 125 mg which seems to help some but he continues to forget important events. My question is this: He has worked in a body shop for many years......almost 40 years now. He has had his own body shop for at least 20 of those years. We ve only been married 7 years so I don t know if he has taken the proper precautions to protect himself from paint, primer, fumes, etc. He also does some mechanic work on the vehicles he buys. Could exposure to any of the above be causing any of these symptoms? The neurologist said that if his symptoms return he would need to do some neurological testing to determine if there is anything else going on. We are both worried about the possibility of Alzheimer s or Dementia but the scans did not show that. Thanks.