Andrew Dibner, a psychologist who created a new segment in the health care industry when he invented a medical alert system that let elderly and disabled people call for help when they cannot reach a telephone or knock on a neighbor’s door, died on Saturday in a memory care facility in Peoria, Ariz. He was 93.

Dr. Robin Dibner, his daughter, said the cause was complications of Alzheimer’s disease.

Mr. Dibner was a psychology professor at Boston University with a special interest in the problems of old age in 1972 when one day, while shaving, he pondered what happens when a frail person, living alone, falls and cannot move.

“How does someone who can’t call for help call for help?” he recalled wondering.

He and his wife, Susan Schmidt Dibner, a sociologist, answered the question in 1974 by starting Lifeline Systems, widely recognized as the first company to sell personal emergency response systems in the United States. She remained his partner in the company.

Lifeline prompted other companies to enter the business, most famously LifeCall, whose well-known television commercial featured an older woman lying on the floor, saying, “I’ve fallen and I can’t get up!”