Researchers examined nearly nine million American death certificates from January 2020 to December 2022, covering 443 occupations. Taxi and ambulance drivers had the lowest risk of dying from Alzheimer’s disease of any of them. After adjusting for age, sex, race, ethnicity and education, roughly one in a hundred taxi and ambulance drivers died of Alzheimer’s, against one in sixty across the population.
The pattern did not extend to bus drivers or aircraft pilots.
That exclusion is the finding. It is not driving, not sitting, not shift work, not being outdoors. Bus drivers and pilots follow fixed or predetermined routes. Taxi and ambulance drivers do continuous real-time navigation: locating yourself in space, tracking a destination, and updating a mental map as conditions change.
The mechanism proposed is the hippocampus, which governs memory and spatial navigation and is among the first regions Alzheimer’s damages. Problems with orientation are among the earliest signs of the disease, sometimes appearing before obvious memory loss. Notably, the low Alzheimer’s mortality among these drivers was not seen for other forms of dementia, which is what makes the hippocampal explanation plausible rather than merely convenient.
The supporting evidence goes back to a landmark study in 2000, which compared licensed London taxi drivers with people who did not drive cabs. To earn that licence, a cabbie must memorise more than 25,000 streets within a six-mile radius of Charing Cross, a process known as The Knowledge that takes three to four years. The drivers had measurably more grey matter in the posterior hippocampus, the region tied to storing large-scale spatial maps, and the volume tracked with years of experience. Built through practice, not inherited.
Then the part that matters for anyone thinking about places rather than jobs.
A 2023 study ran a machine learning model on more than 22,500 people in a national dataset and predicted which zip codes had higher rates of Alzheimer’s with 84 percent accuracy, based purely on how spatially complex the environment was. A follow-up tied geospatial complexity of a person’s surroundings to greater volume in the brain’s navigation regions.
Dense street networks. Numerous intersections. Multiple landmarks. Places you have to think your way around.
Which puts a slightly uncomfortable question to a century of urban planning, because the direction of travel has been relentlessly toward legibility. Wide arterials, numbered grids, single access roads into estates, retail parks reached by one turning. Every one of those decisions removes a small navigational demand, and each removal is individually an improvement.
The old quarter that is impossible to drive through is also the one where the cafe on the corner survives, because the corner is a place rather than a coordinate. That has always been argued on charm. This is a different argument for the same thing.
Hatim Sharif, the civil engineer who wrote the piece, notes that spatial reasoning can be trained and that the opportunities already exist widely.
The cabbie spent four years learning 25,000 streets to get a licence.
