Anne and Bill Uhler have been married 49 years. Bill was diagnosed with Parkinson’s-related dementia in 2012 and Anne has been his primary caretaker since that time. Travis Heying The Wichita Eagle

Can a person can delay or reduce their chances of getting Alzheimer’s? The answer is not straight forward.

Late-onset Alzheimer’s, the most common kind, typically starts after age 65. The Alzheimer’s Association estimates, based on current figures, that a 65-year-old has a 1-in-8 chance of getting dementia before they die, while an 85-year-old has a 1-in-6 chance.

But medical researchers are cautiously starting to believe that the incidence of dementia is falling, according to the New England Journal of Medicine. That means the chance that any particular person will get it seems to be dropping.

They don’t know exactly why. Alzheimer’s is caused by a buildup of protein plaque outside neurons in the brain and twisted strands of the protein inside the neurons. Both slowly kill the neurons, which leads to loss of memory and judgment, confusion and bad behavior, then loss of speech and the ability to walk.

It eventually becomes the underlying reason for a fatal fall, pneumonia or other cause of death.

Age is the top risk factor, according to the association. The older you are, the more likely you are to get it.

But Alzheimer’s is not a routine part of aging, and getting old is not enough to cause the disease.

Other factors include a family history of Alzheimer’s, the APOE-e4 gene, cardiovascular disease, education, social and mental engagement, and traumatic brain injury.

Researchers theorize that the lower incidence comes with greater wealth and better education, factors leading to better overall health; and to specific treatments that lower cardiovascular disease such as the use of statins, anti-hypertensive agents and non-steroidal anti-inflammatory drugs.

The gains are fragile, and a permanent shift could be reversed by generational health factors such as the rise in obesity.

What can be done intentionally to fend it off? That is where it gets hard.

Robin Heinrichs, neuro-psychologist with KU School of Medicine, downplayed how reliable the other factors are in predicting who gets late-onset Alzheimer’s. Those with a family history of it appear to have a slightly elevated risk, but not enough to focus on, she said. Researchers don’t understand the relation between the risk factors and the disease.

“There is a randomness that people are a little unsettled by,” she said.

Alzheimer’s makes up 60 to 80 percent of all dementia, an umbrella term for several disorders marked by a decline in memory, speech, language, judgment, reasoning and planning, and the ability to do everyday activities, such as cooking, paying bills and driving.