I suddenly wore two hats — that of a retired physician who had cared for people with Alzheimer’s disease and now a person living with the same disorder.

I have a special interest in Alzheimer’s disease. For nearly 25 years, I practiced general neurology in Portland, Oregon, and some of my patients had dementia. In 2012, while doing a genealogical DNA search, I inadvertently discovered that I have two copies of the APOE-4 allele, meaning I had a very good chance of getting Alzheimer’s-caused dementia by age 80. I felt gobsmacked. I remember walking down the stairs in a daze after reading the report from the genetic testing service and telling my wife, Lois, “I think I am screwed.”

A year later, I retired at age 62 even though I had no symptoms of cognitive impairment. If I had almost any other job, I could have continued working for a few more years, but in medicine, forgetfulness could have fatal consequences. I suddenly wore two hats — that of a retired physician who had cared for a lot of people with Alzheimer’s disease and now a person living with the same disorder.

I had been taught, in medical school in the 1970s and even during my neurology residency in the 1980s, that Alzheimer’s disease progresses from onset to death in about three to five years, and nothing can be done about it. Neither statement is true.

In hindsight, my first symptom of Alzheimer’s disease was a gradual loss of smell that I first noticed in 2006. This was accompanied by odd olfactory hallucinations that smelled like baking bread mixed with perfume. I didn’t have any measurable cognitive impairment until 2015, when I had significant trouble remembering words, including the names of friends and colleagues.

I had a PET scan as part of a research study, which showed my brain had the beginning of abnormal tau protein, a key part of diagnosing Alzheimer’s. When the scans were repeated in 2018 and 2022, the tau protein can be seen spreading through my brain.

We now know that the first signs of Alzheimer’s disease, beta-amyloid plaques, can be seen in the brain up to 20 years before any cognitive changes. Tau-containing tangles start to form later, about two or three years before the onset of mild cognitive impairment. There is a variation in the speed of progression from mild impairment to full-blown dementia to death, probably about eight to 12 years on average.

I am now 73, and I have had mild cognitive impairment for roughly five years, followed by mild dementia for about four years. We don’t yet have a way to stop this progression, but what have I been doing to slow it?

There are lifestyle modifications that help, and they also decrease the likelihood of getting it in the first place.

Top among them is aerobic exercise. Multiple studies have shown up to a 50 percent reduction in the chance of getting Alzheimer’s disease for people who exercise regularly. The only group that doesn’t seem to benefit from exercise are those who already have dementia. The sooner you start, the better.

I started exercising daily in 2012 as soon as I learned that I was on the Alzheimer’s trajectory. Recent evidence shows that tai chi can help people who already are experiencing cognitive impairment.

The data for adopting a plant-based diet are almost as strong as exercise. I follow a variant of the Mediterranean diet called the MIND diet that includes eating foods with increased  flavonols such as nuts and certain vegetables. Many experts now recommend avoiding alcohol, especially for people with a family history of dementia. Recently, I gave up my daily glass of beer or wine. Frankly, I have been surprised that nonalcoholic beer tastes quite good.

Staying mentally active is very important. For me, my most important brain exercise is reading and writing. I do a crossword puzzle every day while eating lunch, and I enhance the brain benefit by looking up words I don’t know. Staying socially engaged is important but increasingly difficult as dementia progresses. It’s best for me to socialize with just one or two people at a time. Getting at least 7½ hours of sleep each night appears to reduce the chance of getting dementia.

What about drugs? We now have two FDA-approved drugs,  lecanemab and donanemab, that are effective in removing beta-amyloid from the brain, but they only slow cognitive decline by about 35 percent. They can also have lethal side effects in patients with two copies of the APOE-4 allele, like me. After only four monthly injections of aducanumab (a cousin of lecanemab) during the phase 3 trial, I developed swelling and bleeding in my brain requiring a stay in an intensive care unit and about four months to recover. The drug has since been discontinued by its manufacturer.

These treatments represent an important step forward in understanding the neurobiology of Alzheimer’s disease, but they should not be used by everyone.

So I have learned that Alzheimer’s disease is not the rapidly progressive dementia I was taught about in medical school. It is a slowly progressive disease that is asymptomatic for up to 20 years. Mild symptoms of cognitive impairment may be annoying but usually can allow normal activities for another five years or so. Even work may be possible with accommodations. Once someone has dementia, unable to live independently, lifestyle modifications and medications do not seem to be as effective. In my experience, it is critical to manage Alzheimer’s disease in the early stages to postpone the onset of dementia. Don’t wait for the horses to get out of the barn.

Daniel Gibbs has published two books about his experiences with Alzheimer’s disease, “Dispatches From the Land of Alzheimer’s” and “A Tattoo on My Brain: A Neurologist’s Personal Battle against Alzheimer’s Disease,” which was made into a documentary film that can be streamed on Paramount Plus. Gibbs also has a blog.

https://wapo.st/3ZWztZv