Why do Ambulance Drivers Rarely Die of Alzheimer’s?

It's not just ambulance drivers; taxi drivers fall into the same happy category too.

It's all about spatial awareness

According to the results of a study examining the death certificates of nearly 9 million people in the U.S., taxi and ambulance drivers are less likely than workers in almost any other job to die of Alzheimer’s disease. After adjusting for age, sex, race, ethnicity, and education, roughly 1 in 100 taxi and ambulance drivers died of Alzheimer’s, compared with 1 in 60 people overall.

However, this remarkable difference in mortality rates does not extend to other driving jobs. The researchers concluded that the key to reducing the risk of Alzheimer’s was not driving itself but continuous real-time navigation: the constant work of locating yourself in space, tracking a destination, and updating a mental map as conditions change. Drivers whose jobs relied on fixed or predetermined routes, like bus drivers and aircraft pilots, didn’t seem to experience a similar advantage.

But why? Researchers postulate that the association between navigation-heavy work and lower Alzheimer’s risk revolves around the hippocampus, a part of our brains that governs memory and spatial navigation. It’s one of the first brain regions that Alzheimer’s damages: Problems with spatial navigation and orientation are among the earliest signs of the disease, sometimes surfacing before obvious memory loss.

This latest study follows one from 2000 when neuroscientists compared the brains of licensed London taxi drivers with those of people who did not drive cabs. Their findings provided the first evidence via structural imaging that regions of the adult brain can measurably change under sustained navigational demand. To earn a license, London cabbies must memorize more than 25,000 streets within a 6-mile radius of Charing Cross, a challenge known as “The Knowledge” that takes three to four years.

The study found that London cabbies had measurably more gray matter in the posterior hippocampus, the part of the brain linked to storing large-scale spatial maps. Indeed, this gray matter expanded with experience: The longer someone had driven, the larger that part of the brain.

Together, these two studies make a compelling case: Work that intensively exercises the hippocampus may reshape it, and that reshaping may protect against one of the most feared diseases of getting old. However, if you are not a taxi or ambulance driver, it's good to know that major trials have begun for a medicine that has the potential to halt the degenerative condition in its tracks before symptoms even appear.