Can someone tell me if this is still stage 1 Alzheimer's or what stage it could possibly be?

I agree with the others that something is going on. Swelling doesn't come on that suddenly unless something has gone awry. Maybe his legs were hurt in the fall. Or maybe there is something happening inside of him that contributed to his falls, e.g. a heart condition. He needs some serious testing, including urinary, liver, and heart. Do you think he could be diabetic?

One really can't diagnose Stage 1 Alzheimer's, because there are no symptoms in Stage 1. It is the pre-dementia stage. Since the forgetfulness came on suddenly, I would suspect either a UTI or another metabolic imbalance. He needs medical assistance today.

Swollen legs, ankle and hands are a red flag, especially since it seems this happened very quickly. I would take him to the ER, now.

Walter, I found this article here on the Aging Care website that could be helpful. https://www.agingcare.com/articles/Stages-of-Alzheimers-disease-118964.htm

If he is recently disgnosed hopefully he was put on meds to try and help the progression of the disease. My sister talked to my mom daily on the phone. My mom did not really recognize those she had not seen often. At one point i had to say to my brother that he shoukd tell mom he wanted to kiss her before he did. I was beside and could see fesr in her eyes because she had no idea who this man was and why he was coming so close to her face. If you have not seen a neurologist you should get to one asap. Once my mom was diagnosed. The neuro doctor was basically the primary doctor that mom eould see. Good luck

Forget about stages. First off, get him to the doctor or urgent care and have him tested for a uti or other infection. Second, what kind of doctor dxed the the Alzheimers ? If it was anyone other that a neurologist who had extensive neuropsych testing done, I would seek a better diagnosis.