“It has literally been hell,” said Ms. Schnepp, a strong believer in the right to bear arms. “At some point, if you have guns in your life, you need to think about what you’re going to do about that.”

Alzheimer’s, the most common form of dementia, affects 5.1 million Americans 65 and older, a number that is expected to nearly triple by 2050. People with the disease can become aggressive and hallucinate, sometimes lose peripheral vision, fail to recognize loved ones and forget the purpose of an object. While those in the early stages may handle a gun responsibly, the risk of trouble grows as the disease progresses, doctors say.

The few studies that examine gun ownership among people with dementia and other cognitive disorders suggest that families are not removing guns after a diagnosis. In one assessment, which examined 106 patients at a South Carolina clinic, 60 percent of them had a firearm at home. In another, involving 495 people at a Cleveland clinic, 18 percent did.

Perhaps that is because many relatives do not know how to approach the subject. While doctors are legally permitted to give advice about gun storage, they often do not, according to a paper published in May in Annals of Internal Medicine. “Some physicians believe it is against the law to discuss firearms,” the authors wrote. Others are unfamiliar with “what to say during firearm safety counseling and how to say it.”

In Asheville, N.C., Dr. Virginia Templeton runs an outpatient clinic for people with dementia and said that 40 percent of clients had a gun at home. She asks about this on an intake form, and counsels caregivers in the appropriate method of removal.