LES PIEUX, France — On a sunny but chilly June morning, Dr. Martial Jardel took his black motorcycle out of his camper van, put his helmet on and started the engine. For his last day on Normandy’s Cotentin Peninsula, he was ready to hit the road along the English Channel to visit a patient.

Michel Piquot, 92, standing on his doorstep in blue slippers, was waiting impatiently.

“When was the last time you had a blood test?” Dr. Jardel asked after arriving at the single-story house, speaking louder for the hard-of-hearing Mr. Piquot, a former employee of an aviation company.