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Decreased Alzheimer’s Disease Incidence in Taxi Cab and Ambulance Drivers

Writer's picture: FibonacciMDFibonacciMD
6 days ago

In a study published in December 2024, researchers correlated almost 9 million U.S. death certificates with occupational data for the presence of Alzheimer’s disease listed as a cause of death. They used data from a national data registry of U.S. deaths. 


They reported that taxi cab drivers and ambulance drivers have statistically lower risks of developing Alzheimer’s disease than all the other 441 occupations they compared them to.  Airline pilots, sea captains and bus drivers all had higher Alzheimer’s disease risk than taxi and ambulance drivers. This is in contrast to the finding that vascular and unspecified dementias were not found to be less prevalent in taxi and ambulance drivers than in other professions. 


A previous study had looked at MRI scans of London taxi cab drivers and reported that taxicab drivers had, on average, larger hippocampus volumes than control subjects. They also found that hippocampal volume correlated to the number of years worked as a taxi driver. The authors of that study suggested that the constant use of navigational skills possibly increased the size of the hippocampus.


The authors of the current Alzheimer’s study postulated that similar changes in the brain’s hippocampus might be protective for Alzheimer’s disease. They also stated that the reason bus drivers did not have the same benefit might be due to fixed routes that did not require active navigation. 


Weaknesses of this study include the fact that the mean age of death was lower in taxi and ambulance drivers than other occupations, being 64.2 to 68.7 years compared to a mean of age of death of 74.3 for the other professions. Thus, taxi and ambulance drivers tended to die younger which could have affected the results, even though the authors state they adjusted the statistics for age. The cause of death on the death certificate is determined by health care provider and documentation may be incomplete leading to incomplete data. A person may have held multiple jobs in their life as opposed to one which could lead to inaccurate profession assignment.  Finally, there may be unknown confounding variables not taken into account which might lead to inaccurate results. One thought is that perhaps certain ethnic groups, who may have either increased or decreased risk of Alzheimer’s disease, might tend to cluster in certain occupations.  


Comments: 

In this interesting study, taxicab and ambulance drivers were found to have lower rates of dying from Alzheimer’s disease than other professions, although there was no protection against vascular and undefined dementias. The authors postulated that the active navigational process involved in these professions increased hippocampal size and might be protective. There were a number of weaknesses in the study design that might have affected the results, including the younger age of death of taxi and ambulance drivers than those in other professions. 

However, the issue of brain plasticity (the brain's ability to reorganize and rewire neural connections) by environmental stimuli is an intriguing one. In other studies, it had been suggested that individuals with conservative political views have larger brain amygdalae than those with more liberal views.  The question being, does a genetic predisposition to having certain areas of the brain being larger lead to a certain way of thinking and viewing the world, or does one’s approach to life lead to hypertrophy of some areas of the brain. 


 


 

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