出租车司机为何少患阿尔茨海默症：空间推理或保护大脑

Figuring out a circuitous route between point A to point B can strengthen your brain. justhavealook/iStock via Getty Images Plus

Taxi and ambulance drivers are less likely than workers in almost any other job to die of Alzheimer’s disease. That was the surprising result of a 2024 study examining the death certificates of nearly 9 million people in the U.S.

These findings stopped me in my tracks because those two jobs rely on the same thing as my own work: maps.

I have spent more than two decades staring at maps. Not paper maps on a wall, but digital ones with multiple layers: flood boundaries draped over census blocks, car crash hot spots plotted against road geometry, and satellite readings of rainfall stitched across river basins. Much of my work as a civil and environmental engineer is done through GIS – that is, geographic information systems. Engineers like me hold several spatial relationships in their minds at once, reasoning about where things sit relative to one another across scales ranging from a city block to a whole watershed.

I always assumed that spatial reasoning across map layers was purely professional. But that study on taxi and ambulance drivers made me wonder whether all that mental work might be doing something good to the brain.

Taxi driver brains

Of the 9 million death certificates from January 2020 to December 2022 that researchers examined, taxi and ambulance drivers had the lowest risk of dying from Alzheimer’s disease out of 443 occupations. 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.

This pattern did 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.

Researchers believe the association between navigation-heavy work and lower Alzheimer’s risk centers on the hippocampus, a part of the brain 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.

In one landmark 2000 study, 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.

Can you memorize 25,000 streets and how to navigate them?

The researchers found that London taxi drivers had measurably more gray matter in the posterior hippocampus, a brain area tied to storing large-scale spatial maps. That volume tracked with experience: The longer someone had driven, the larger that part of the brain. The change was built through practice, not inherited. While people who are good at navigation might gravitate to this kind of job, the job itself does have an impact on the brain.

Together, these two studies make a coherent case: Work that intensively exercises the hippocampus may reshape it, and that reshaping may protect against one of the most feared diseases of aging.

Where map specialists fit in

Cartographers, urban planners and geospatial analysts spend their working days in sustained spatial reasoning. A geographic information system specialist might use a computer to overlap population data on flood exposure maps to find who is at risk, or read satellite imagery to map land cover after a wildfire. Researchers juggle several layers of data, coordinate systems and scales at once.

Does spatial reasoning through a screen engage the hippocampus the way moving through a real city does?

While a taxi driver navigates from inside the scene at street level, GIS researchers picture space from above as a map – what cognitive scientists call allocentric reasoning. But these two perspectives overlap in the brain: The hippocampus also builds maps from outside viewpoints, not just from a navigator’s own position.

Research on cognitive maps points toward the same conclusion as the study on taxi drivers. In 2023, researchers ran a machine learning model on more than 22,500 people in a national dataset and were able to predict which ZIP codes had higher rates of Alzheimer’s with 84% accuracy based on how complex the environment was. Those living in spatially complex surroundings – the kind that force active map building, such as dense street networks with numerous intersections, diverse points of interest and landmarks, and multiple path options – were less likely to develop Alzheimer’s.

Living in spatially complex places challenges your brain. fhm/Moment via Getty Images

A follow-up study tied geospatial complexity in one’s environment to greater volume in the brain’s spatial navigation regions. The researchers hypothesized that routinely building cognitive maps exercises the very circuitry that Alzheimer’s attacks first. Repeatedly engaging the cognitive systems involved in spatial navigation could help delay symptoms of disease.

However, these two studies focus on where people live, not the work people do. Whether spatial reasoning through a screen exercises the same circuitry as real-life city navigation remains untested.

Protecting your brain

The implications of whether sustained spatial reasoning protects the brain reach beyond mapmakers and cab drivers. Studies have repeatedly found a link between mentally complex occupations and delayed cognitive decline and lower dementia risk, even after accounting for education.

Research on cognitive reserve – the brain’s capacity to continue functioning despite disease – can help explain why two people with a similar disease burden can show markedly different levels of cognitive impairment. If demanding spatial thinking protects the brain, then how societies design schooling, professional training and retirement all become questions of brain health.

Spatial reasoning can be trained, and training opportunities are already widespread. GIS and remote sensing instruction are available through geography, engineering, public health and environmental science programs worldwide.

If sustained engagement with spatial reasoning can help the brain strengthen the circuitry that Alzheimer’s attacks first, its value reaches well beyond the technical skills it builds.

• Neurodegenerative disease
• Neuroscience
• Spatial
• Brain
• Geography
• Hippocampus
• Civil engineering
• Geographic Information Systems
• Alzheimer's disease
• Maps
• Brain health
• Spatial reasoning
• Taxi drivers
• Spatial memory
• Spatial skills
• GIS
• Mental maps
• Alzheimer's risk