Taxi drivers offer a clue to Alzheimer's risk | Hacker News Reader

Taxi drivers offer a clue to Alzheimer's risk

wsj.com

127 pointsjulienchastang109 comments

A study came out in 2000, back when I was driving a taxi, showing that London cabbies with "the Knowledge" had changes to their brain anatomy.[0]

My girlfriend at the time spotted it in a college course and showed it to me. I remember her joking that she was only with me for the size of my hippocampus.

I would hypothesize that it's more related to spacial/geographic memory than simply navigating spaces one visually perceives. My guess is the effect would be much less pronounced in people who drive for a living now relying on GPS maps.

London taxi drivers, apparently, still must pass the notoriously difficult Knowledge test.[1] A similar (but less rigorous) test was required for Los Angeles cab drivers when I drove. And of course, if you weren't familiar with the street where your next call was (or where your passenger wanted to go), you had only seconds at a red light to leaf through the enormous Thomas Guide and memorize how you would get there.[2]

[0] https://www.pnas.org/doi/full/10.1073/pnas.070039597

[1] https://london-taxi.co.uk/the-knowledge/

[2] https://archive.org/details/losangelescounty0000thom/page/n9...

There have been a few HN threads about that over the years—here are some (I think there may be others?)

Streetwise (1996) – BBC doc about The Knowledge (memorising every London street) - https://news.ycombinator.com/item?id=26581295 - March 2021 (1 comment)

The Knowledge of London for cab drivers - https://news.ycombinator.com/item?id=25485509 - Dec 2020 (45 comments)

The Guardians of London's Black Cab 'Knowledge' - https://news.ycombinator.com/item?id=10717003 - Dec 2015 (20 comments)

London’s Legendary Taxi-Driver Test Puts Up a Fight in the Age of GPS - https://news.ycombinator.com/item?id=8585781 - Nov 2014 (105 comments)

World's Hardest Geography Test - https://news.ycombinator.com/item?id=8306536 - Sept 2014 (1 comment)

For London's Cabbies, Job Entails World's Hardest Geography Test - https://news.ycombinator.com/item?id=8295264 - Sept 2014 (68 comments)

I think it’s also in a Malcom gladwell book.

I would hypothesize thats its related to getting ousted from the job as a taxi driver if you have just early Alzheimer’s

meaning no cognitive benefits from just navigating around a city more often

Brilliant comment—-The effect could easily be an ascertainment bias that is downstream of winnowing 55-70 year-old drivers who cannot hack route selection effectively anymore. They drop out and take on other jobs.

I'm not so sure. The study didn't stipulate that taxi driving was the patient's last occupation, nor how long they did the job for.

Also, with Alzheimers, aren't older memories the last to go? A driver would probably be more likely to have trouble finding their keys before they forgot the streets they'd been driving for 30+ years. At that point, it would be hard to train for another job.

Additionally, I've never heard of a cab driver losing their license for getting confused en route. Taking the wrong way on purpose can lead to some disciplinary action, but even that is rarely if ever pursued.

I am not sure either. The authors (more correctly, the author of the review of the the parent paper) imply that the constant challenges to adapt to complex spatial navigational tasks is the most likely explanation. Familiarity with routes is not the key variable (no bus driver benefit). It is active navigational adjustment or perhaps just ascertainment. Controlling for ascertainment bias would be possible but hard because you would face secular confounds (e,g., impact of COVID-19 on taxi drivers vs other professions).

By the way, the original l”London taxi drivers have larger hippocampii paper” was NOT replicated. So sad since this is such a fun story.

From a programmer's and former taxi driver's perspectice, finding a fuzzy path through something chaotic and shifting like a city optimizes for very different logic than finding a path through a maze or a jam of vehicles. It's reducing from a big picture versus trying to iterate solutions from a small picture. And I can't tell you how many times I get in a lyft these days and know better than the GPS how to get around a traffic snarl, because pathfinding generally doesn't consider what might happen to traffic 30 minutes from now given the current conditions (if everyone is headed northeast to a concert, for example).

Here is there selection criterion and justification:

“occupations involving extensive day-to-day navigation, with often unpredictable, real time navigational demands.”

All subjects died between Jan 1 2020 (COVID) to Dec 31, 2022.

There was no data on duration between active employment in listed employment categories and age of death. This is a problem given the fact that Uber and Lyft have radically changed the taxi industry in 101 ways that will interact with age of drivers. Not true of ambulance drivers.

Mean age of death of target groups: 64 (ambulance) to 68 years (taxi) and mostly men. Both values are awfully (sadly) low. I want to understand the poor expectancy of ambulance drivers. Is it stress?

And here is summary of their analysis:

>For each occupation, we first calculated the percentage of deaths due to Alzheimer’s disease and the mean age at death in years (ie, average life expectancy). We plotted the association between these two variables, with each observation reflecting a single occupation. The purpose of this analysis was to illustrate the need to account for the person’s age at death since the risk of Alzheimer’s disease rises with age and therefore Alzheimer’s mortality would naturally be lower in occupations with a lower life expectancy.

And here is their discussion on ascertainment bias (great job):

>Firstly and perhaps most importantly, selection bias is possible because individuals who are at higher risk of developing Alzheimer’s disease may be less likely to enter or remain in memory intensive driving occupations such as taxi and ambulance driving. This could mean that the lower Alzheimer’s disease mortality observed in these occupations is not due to the protective effect of the job itself but rather because those prone to the disease may have self-selected out of such roles. However, Alzheimer’s disease symptoms typically develop after patients’ working years, with only 5-10% of cases occurring in people younger than 65 years (early onset).1114 While subtle symptoms could develop earlier, they would still most likely be after a person had worked long enough to deem the occupation to be a so-called usual occupation, suggesting against substantial attrition from navigational jobs due to development of Alzheimer’s disease.

>> The purpose of this analysis was to illustrate the need to account for the person’s age at death since the risk of Alzheimer’s disease rises with age and therefore Alzheimer’s mortality would naturally be lower in occupations with a lower life expectancy.

Just a nit: This sort of analysis seems lazy, because while it's true that without advanced age one's likelihood of dying from Alzheimers is lower, it's also true that without Alzheimers one's likelihood of dying at advanced age is lower. The dataset used for the non-Alzheimers death rate should be adjusted for what the death rate would be if Alzheimers didn't exist, not the death rate from all other age-related causes in a world where it does exist.

Only a tiny group of people with Alzheimer show symptoms at their 30s, while practically nobody at their 20s (early Alzheimer)

okay. that might be a medical industry distinction for early Alzheimer’s, I am referring to a colloquial definition of “passengers noticed it and reported the driver and their their license got revoked so they arent a taxi driver anymore”

The vast majority of people don't report when taxi drivers get a little lost, for most something really serious must occur to report, e.g. crashes, overcharging

I agree with that. I don’t think passenger reports leading to taxi driver termination is a likely path.

But if a taxi driver has cognitive decline which imparts their ability to route plan effectively that would increase their stress, and preceived workload. What i think can be more likely is that those drivers would self-select out of the pool of taxi drivers. Subjectively they would say something like “it was too much trouble, there are better jobs elsewhere, etc” but what might be behind is the early symptomps of Alzheimer.

This is not how taxi driving works / worked. Let me give you a slice of taxi driving here, since I did it for some years.

99% of taxi drivers in America are immigrants. I was one of the few exceptions, one of only 3 native born drivers in Los Angeles that I knew of. (One was in a rock band, one was on drugs and slept in different motels every night; then me). The young immigrant drivers might be from anywhere, most of them have no education. But the drivers in their 50s to 70s (all men) who are still working are all either Korean or Russian immigrants. They have university degrees, they were engineers or factory managers in Russia. They're highly educated and extremely intelligent. They're also excellent at committing petty fraud.

There is absolutely no such thing as one of these people quitting their job as a taxi driver to do something else. Never happened. They will spend all day playing poker on the hood of their cab waiting in line at the airport and saying that "driving taxi is killing my soul", they will die in the driver's seat before quitting because they think they've become too out-of-touch to continue. And by no means would they get some other job if they quit. The scenario in which they quit and get another job just doesn't exist.

For a rough analog, go to a casino and look at the people over 60 who are playing a slot machine who used to have a somewhat respectable career as a service manager at a car dealership in the mists of the distant past, and consider the chances of them quitting gambling and going to rehab and then training to be a bank teller, and actually getting a job as one. That's about the chance of a 60 year old cab driver in LA quitting before he dies.

Driving taxi is/was, among other things, deeply addicting as a gambling pathology. Any given ride could get you killed, get you robbed, or get you laid. And driving around picking up strangers at 4am with a wad of $500 in your pocket is a thrill. The only difference between you and the cops was that you were unarmed and the cops would find your body. You were picking up the same people.

Very cool story. But so what? The people you describe are the ones who stuck with it. The people for whom it was not working went and found something else. So you would not describe them as taxi drivers. You would describe them as used car salesman, or grocery store casheer, or simply bum on the street.

That wouldn't surprise me in the least.

Beyond the basic health things (weight, activity, smoking, diet, blood pressure) just about everything that they come up with that relates to living longer could also be filtering. I remain unimpressed because of this.

A friend had a job installing security equipment and kept Thomas Guides in his car. This is only the second time I’ve seen the name.

I’m so glad to live now, as I used to get very lost before GPS.

Here's a link to the actual study, which is very readable:

https://www.bmj.com/content/387/bmj-2024-082194

I wonder if this also applies to people that live urban environments that don't drive and have to navigate walking or using the subway.

From my anecdotal evidence, it does seem that the average elderly person in NYC is way more active and social than an elderly person in the suburbs. But of course, it could be that people that live in cities self-select.

The fact that they have physical exercise (i.e. walking) probably contributes a lot..

They sort of self-select by the ability to earn enough to afford living in a city like NYC. There's enough low-income n-th generation inhabitants though to form a control group.

Is there a correlation between income and incidence of alzheimers? I wasn't aware of one.

The more money you have, the longer you live?

Yes but I'm not talking about quantity of older people in total, I'm talking about what percentage of them get a disease.

With cancer, which is also more likely the older you get, studies show that the chances of dying from it are about 12% higher in the poorest counties than wealthier counties in the US. That is despite people in those counties having a shorter lifespan from all other things as well.

So my question in response to the parent's throwaway class warfare riff was: Given two people who survive to the same age, let's say 80, is one more likely to get Alzheimers than the other based on income? The article here would suggest otherwise, given that taxi drivers and ambulance drivers are among the least well compensated workers and yet strangely have 1/3rd the rate of Alzheimers.

[0] https://www.cancer.gov/news-events/cancer-currents-blog/2020...

Sure, but in general people care about their future risks.

So the difference between when you look 30 vs 80 year olds makes it important to define what you mean when you say more likely to get it.

My point is, if you live to be 80, you won't be any less likely to get Alzheimers if you're rich. So there's not really a correlation between 90 year olds walking around NYC dementia-free and the fact that they're wealthy enough to live to 90.

I lived a couple years in a working class farm town in Spain where the old people were mostly not wealthy by but were really physically fit and mentally sharp. I think it was due to them having constant social interaction, every day walking around the plazas talking with their elderly friends. Some of these people were living alone in their mid-90s, and their diet mostly consisted of fried sardines, pork, olives, and cheap local wine. So living a good full life may be better protection against the ravages of dementia than living a wealthy one.

Wealthy people are less likely to get Dementia, which has multiple causes one of which is Alzheimers.

https://www.alzheimersresearchuk.org/news/wealthy-linked-red...

No correlation known to me, but likely still a bit of self-selection, at least for some large swaths, which can potentially bring in a confounding factor.

There’s plenty of subsidized senior housing in New York. My grandmother is in a complex like that right now, and all she does is collect SS.

Even among people who live in NYC, the elderly people who are outside going for walks and taking public transport are going to be healthier. If they're sicker or weaker, they would be more likely to take a cab or stay indoors and have things delivered.

If they’re sicker or weaker, they would be more likely to leave the city.

It is a difficult place for anyone, but especially for those with trouble climbing lots of stairs, handling icy surfaces, repeatedly shedding and putting on clothes, etc.

Or who are too old to sustain the illusion that their income is on an upward trajectory, and the current difficulties thus temporary.

What about navigating all those Walmarts and parking lots?

When the weather is cold, driving means you’re not outside nearly as long when you go shopping, and you can go less often, in better weather.

The shorter your exposure to weather extremes the more you can tolerate and the less you need to be prepared. Consider some extremes of human tolerance: The 300 club. 200F (sauna) to -100F (south pole winter), naked other than foot protection. IIRC the requirement is to walk around the world in that -100F condition. Or, for very limited exposure: cryotherapy. I'm finding conflicting numbers on just how cold it can go. WebMD says some chambers go as low as -300F, although any chamber that cold your head stays outside. (That level of cold is done with nitrogen, the chamber itself will be an anoxic environment.) It's normally done with protection for all the small bits that stick out, but otherwise minimal attire.

Does navigating spaghetti code count as well?

I think navigating code definitely has a relationship to navigating meatspace, and the ability to internalize a view of the code space makes for a good programmer.

I'm long retired now, but attribute a lot of my programming ability to having had very poor sight in early childhood thus having to keep a mental map of my surroundings.

Navigating it? How about writing it?

Sure hope so. Staying mentally sharp into old age is one of the things I comfort myself with when I am putting in long hours and just want to go outside.

Having a healthy cardiovascular system, like you might get from brisk walks, seems important for mental health

I do wonder though if its cause and effect are the wrong way.

Perhaps the type of person who can remember enough to get the job and be good at it is already less likely to get Alzheimers, and we just selected for those people.

I think this is not very likely though

Yeah, I don't think the selection into being a taxi driver is that intense though (at least in 99% of markets), it's a fairly low wage job

They should replicate the study in the UK where the test to become a licensed taxi driver is extremely hard and requires years of study to memorize I believe close to 30,000 street names.

just because it's low wage and a lot of people know how to do it, doesn't mean it isn't cognitively demanding

and, driving is one of the most lethal activities that people commonly do in the modern world. according to osha 'transport incidents' represent 39% of all occupational fatalities

https://www.bls.gov/charts/census-of-fatal-occupational-inju...

presuming an absence of any survival bias is probably a little cavalier.

Taxi drivers often have a shady side gig in being a police informer, drug dealer etc. Also practically all valuables which clients forget become theirs.

I think it’s more like those that were taxi drivers that got Alzheimer’s quit earlier than those that didn’t get it. So it’s more like survivor bias.

This is just typical for science "journalism".

Take a study that only shows a correlation, and then write a clickbait article about causation.

The actual study says:

>Importantly, our study design has several limitations that limit causal inference and result in the possibility of other explanations, including unmeasured confounding from biological, social, or administrative factors. Firstly and perhaps most importantly, selection bias is possible because individuals who are at higher risk of developing Alzheimer’s disease may be less likely to enter or remain in memory intensive driving occupations such as taxi and ambulance driving.

>...

And

>Our large scale epidemiological findings raise novel questions about the linkage between taxi and ambulance driving and Alzheimer’s disease mortality. While these findings suggest a potential link between the demands of these occupations and reduced Alzheimer’s disease risk, this study design does not permit interpretation of a causal effect between occupations and risk of Alzheimer’s disease mortality or neurological changes in the hippocampus

I have noticed this for many years that when a study passes from the authors to science journalists to regular journalists to social media, information is lost at each level just like in Chinese whispers.

> This is just typical for science "journalism".

This one is not that bad.

First, and it is the most important point, it links to the actual studies. So many articles don't do that... Maybe some journalists should be told that unlike paper, the web has hyperlinks, but here, the author knows.

More than that, the article doesn't mentions a single study, and is cautious regarding potential causation. The article title doesn't explicitly mention causation, just that "taxi drivers offer a clue". It is clickbait, but clicks is how they get paid, as mainstream journalists, they don't really have a choice.

As a mainstream news article I'd give it a 9/10. It has sources, makes an effort that goes beyond interpreting a single paper, and talks about shortcomings.

Recently related:

Herpes virus and repeated head trauma linked to Alzheimer’s, study finds (2025) https://news.ycombinator.com/item?id=42629076

Why Alzheimer's Scientists Are Re-Thinking the Amyloid Hypothesis (2025) https://news.ycombinator.com/item?id=42628529

Herpes Virus Might Drive Alzheimer's Pathology, Study Suggests (2025) https://news.ycombinator.com/item?id=42578383

> Taxi drivers may have a lower risk of developing Alzheimer’s because they are constantly using navigational and spatial processing.

It would be interesting to know whether certain kinds of video game play have a similar effect. On the one hand, you don’t do it for 8+ hours a day every day (unlike cab drivers), but on the other hand, there might be a much higher volume of spatial and navigational decisions packed per minute in certain games.

You would be surprised how many people pack in more than 10 hours of Fortnite or similar games.

On the other hand reality is much more complex than any game, so I am not sure if these nav decisions are equivalent.

> On the other hand reality is much more complex than any game

Untrue. A Taxi driver won't have to worry about elevation changes much at all. Zooming around a computer-generated space in a game might have a lot of that.

PvP games can get pretty difficult. You need to remember the map, make a strategy, know which moves and counter moves exist, also make timing-precise input (e.g. active parry frames are 6 out of 30) and not forget to compensate for network latency you have judge by the vibes.

As long as you disable the minimap in game. Which is the correct way to play open world games anyway. Other ways you look at the arrow instead of looking at the environment.

I'm not sure it's equivalent to building a mental map of a 3D space. It certainly might be, but I can also imagine that it might have key differences.

Am I interpreting the data correctly in that, whatever protective effect was found on Taxi drivers and Ambulance drivers, was actually aggravated on Ship Captains and Airline Pilots?

My immediate thought went to the negative effect of sleep quality and work schedules, but I would expect the same sleep strain/stress for Ambulance drivers. A lot going on epidemiology wise but interesting study nevertheless.

Perhaps because those go on autopilot most of the time?

This is basic "mind palace" theory, no? Human memory is linked to navigation; the more you associate memories with navigable places, the stronger your memories will remain.

I have distinct memories as a kid of mapping things into abstract 3d spaces. The number line in my head is a weird 3D thing I still visually navigate whenever I think about numbers.

what's weird is that even while I still use my representations formed as a kid, I don't seem to make new ones when I learn new info, which makes remembering things much harder.

> I have distinct memories as a kid of mapping things into abstract 3d spaces. The number line in my head is a weird 3D thing I still visually navigate whenever I think about numbers.

I do the exact same thing! I wrote a blog post about how I visualise numbers: https://bjoernkw.com/2022/01/02/i-see-numbers/

It's a specific type of synaesthesia called "time-space synaesthesia".

>> I still use my representations formed as a kid, I don't seem to make new ones when I learn new info

Very interesting; why do you think that is?

> the more you associate memories with navigable places, the stronger your memories will remain.

Some of us have a location synaesthesia where thinking about particular topics often evokes a sense of being specific places, looking particular directions, each paired apparently randomly (but durably) with topics. Not sure if this is association (since it seems to form without any associating event with the location) or just signal "leakage" triggering the connection.

This reporting feels a bit superficial, especially given the exciting direction Alzheimer’s research is taking.

It might sound unconventional, but what if taxi drivers, through constant exposure to small amounts of pathogens from travelers worldwide, experience enough immune imprinting to help prevent diseases like Alzheimer’s?

There’s an intriguing study suggesting that one type of Alzheimer’s might be linked to a chronic gut infection that eventually makes its way to the brain.

https://news.asu.edu/20241219-health-and-medicine-surprising...

We are likely on the verge of a scientific revolution that will redefine viruses as key drivers behind some of the most devastating diseases known to humanity.

When I read these headlines I wonder "Causation? Correlation?". Maybe it's addressed in the study but.....

Is it that navigating with you brain is good to prevent Alzheimers? Or are you just more likely to die from something else as a cabbie. Statically speaking your more likely to die, than average, from a traffic related accident. Maybe the all the fumes cause something else terrible that kills you, etc.

It does seem logical to me that using your brain more could help offset these dementia related diseases. But it also seems like if that made a huge difference, we'd see statistically vastly more alzheimers in "low thought" jobs like retail cashiers and people who don't work/retire early vs say... collegiate professors.

May be a simple as being poor and not retiring makes you less likely to develop Alzheimer's.

The correlation alone provides evidence of something worth pursuing and understanding.

They do have some possible causation when considering hippocampus development observed in taxi drivers in other studies.

They adjust for overall lifespan in the study: https://www.bmj.com/content/387/bmj-2024-082194

My guess is it's correlational. It's almost always correlational. Remember the knowing a second language reduced risks of dementia, turned out it was correlational. The real cause was under diagnosis in immigrants who were disproportionately more likely to speak a second language.

Still worth investigating further but dollars to donuts it's not causal.

> Taxi drivers may have a lower risk of developing Alzheimer’s because they are constantly using navigational and spatial processing.

A good reason to not use GPS/GNSS apps too much.

Unless it's going to a location that's completely unfamiliar, I try to only check for red zones before I leave, and then use my familiarity of my city to get to my destination: know my starting point, know a major intersection near the destination, and avoid known-bad locations in between. If I get lost I can always pull out the app to re-orient.

Agreed - I use GPS to do the initial pathfinding - in much the same way I'd use a paper map in the old days.

It's part of why I have a good sense of direction.

Even when using it to go someplace unfamiliar you can pay attention and try to spot features of the area that you can use later to orient yourself if you ever want to navigate there again but without GPS.

I wonder if that would sufficiently engage your navigation and spatial processing to give some of the same benefits the study found?

I like to leave the map open with no route set. Then I can look for shortcuts or check the traffic but I get to run my own routing algorithms (which I often find to be much more flexible and dynamic).

Before GPS navigation apps (I was a kid), I had to either print the whole route or bring a map of my city. When I didn't use such aids I would get lost, and I still do.

A whole generation now uses navigation, is the prediction that there will be an increase in Alzheimer’s in this new generation due to reduced navigational processing?

Alzheimer’s is heart disease for the brain. Some even say it’s a form of diabetes. Using your brain less definitely increases risk.

Not sure how that compares to era where most people didn’t use google maps, but if you use google maps, you are using some part of your brain less especially memorizing or trying to reverse a route from memory. Or that if you can’t remember very well, you wouldn’t last long as a taxi driver(survivor ship bias)

Did this study identify who had the APOE4 gene?

Another study https://www.nature.com/articles/s41590-023-01627-6 suggests the APOE4 gene may be preventing immune cells in the brain from switching to the defensive "clean" mode.

I know my mother's hippocampus was smaller than something like 94% of people her age when she was diagnosed 11 years ago.

First signs of AD generally show up in the hippocampus.

Maybe with heavy spatial reasoning activity in that region, the AD mechanism is stunted or interfered with.

I would be curious to know what activities outside of vehicle navigation stimulate the hippocampus equally. I still play a lot of 3D video games.

I remember a study as well where folks who were much more religious also had a lower rate of Alzheimer's. The purported cause was that remembering the hymns/chanting verses forces your brain to be more supple and active, staving off whatever causes it. Will try find it and link later.

The study also shows that taxi drivers have very low lifespan, which of course is highly correlated to ower risk of death by Alzheimer's. They also ignored may other professions with similar or lower Alzheimer's risk.

Overall, it feels suspicious that they ignored other potential explanations for the data.

They adjust for overall lifespan in the study: https://www.bmj.com/content/387/bmj-2024-082194

Does anyone know how to download the data for the charts in the study?

https://www.bmj.com/content/387/bmj-2024-082194

The last one (9/9) has a download link, but none of the others do.

It looks pretty easy to extract from the svg elements, as the aria-label attributes contain everything, e.g. "Urban and regional planners, Colour 2: Grey, Size: 1, Mean age at death, years: 76.82, Risk-adjusted % of Alzheimer's deaths: 1.92". The following seems to work (may need to be inspecting something in the plot iframe):

  a = []; document.querySelectorAll('path.data-point').forEach(e => { a.push(e.ariaLabel); }); console.log(a.join('\n'))

As said the last time this was posted

Its because taxi drivers with Alzheimer's will get complained about and ousted from the profession before their death

Meaning there are no cognitive benefits to extrapolate from this reality of using your brain, from this study

also probably higher rates of social interaction

I would be really interested in seeing an easily sortable and queriable dataset where you can sort also different causes of death and order them by all professions.

I guess it might be hard to keep being a taxi driver when your brain gradually subsymptomatically deteriorates because of illness that will eventually kill you.

Or taxi drivers with Alzheimer's get fired or quit

Does this control for taxi driver ethnicity?

That's a great question, since we also have this study:

https://www.mcgill.ca/oss/article/food-health/curry-and-alzh...

Could we just be seeing selection effects for very early indicators of alzehimers?

Maze Runner premise? Stimulate brain activity.

so - switch off your sat nav

My DoorDash drivers can barely tie their own shoes. So yes, probably something to this.

My Partner has absolute dogshit spatial memory. I visit a city once and I remember my bearings instinctively, probably due to playing a lot of badly designed mazelike Video games, but she can visit a City several times and still get lost going somewhere she has been before. Should we be worried?

Very flawed study. Looked at profession based on death certificate which is most recent profession.

Those with Alzheimer's likely won't last long as taxi drivers so they find a new profession. And voila their profession from the viewpoint of this study is no longer taxi driver.

Much surprise that our lauded peer review process didn't catch this.

Does most recent profession have more impact than the profession with most years?

It's likely that using ones brain on average more while driving may be a contributing factor. Wayfinding can be a neurally intense activity.

Very specious comment. From the actual article:

> Additionally, death certificates included a field for reported usual occupation (the occupation in which the decedent spent most of their working life), generally completed by a funeral director with help from the decedent’s informant.

So, not as closed-case as you suggest.

Slam-dunking on studies is a top-tier trope on HN. All studies are flawed, but some are useful.

I'd love it if the slam-dunkers occasionally went out and made their own, better, studies to show the world how to do it correctly.

I would love to and could do a better job, the barrier is the current system, it is immediately dismissed as unscientific if done outside of academia or an institution adjacent.

How do you know? Have you tried?

It is certainly harder to get published as an independent researcher, but it is also not unheard of. See discussion at: https://www.researchgate.net/post/Can_a_individual_without_a... Publishing your own study isn't the only way to critisise a hypothesis, you could also just write a rigouros blog post.

Also: Scientists are humans, not godlike beings in ivory towers, thus science lives from participation. If you can find a methological flaw in a study that you are confident about, consider writing them. Who knows, maybe they already accounted for it (and you learn something) or they didn't (and they learn something). Either way they get a chance to clarify or correct.

In the end the goal is to help figuring out what effective Alzheimers prevention looks like. Creating a good discourse around a study can be helpful, but it is also important to be rigorous and communicative when doing so. See as an example the discussion in the peer review of the discussed study, especially the section on survivorship bias: https://www.bmj.com/sites/default/files/attachments/bmj-arti...

If I wrote a study that has a flaw I'd like to be the first to hear about it, just like I like to get a bug report when my software has a bug. Especially if it is a good cause.

Brutal

The author's themselves acknowledged this very point as the most important weakness of the study:

Firstly and perhaps most importantly, selection bias is possible because individuals who are at higher risk of developing Alzheimer’s disease may be less likely to enter or remain in memory intensive driving occupations such as taxi and ambulance driving. This could mean that the lower Alzheimer’s disease mortality observed in these occupations is not due to the protective effect of the job itself but rather because those prone to the disease may have self-selected out of such roles. However, Alzheimer’s disease symptoms typically develop after patients’ working years, with only 5-10% of cases occurring in people younger than 65 years (early onset).

Their explanation however only holds if pretty much all taxi drivers retire at 65 which is clearly not the case. It also ignores the relative prestige of professions. If your father both owned a store and drove a taxi for awhile which will you put on the death cert? Then do airline pilot plus owned a store.

Also dunking on studies is very much the point. The goal is to challenge beliefs and figure out where we are wrong.

We're well short of an obvious slam dunk. We're into a caveat that applies 5-10%% of the time, presented (perhaps disingenuously) as a personal "aha" in a curt, unjustified, and completely dismissive manner on a post that didn't deserve it. Just bad discussion all around, so I stick by the pushback. But it no longer matters - better discussion was had by all in other threads.

From a previous comment:

> Here is there selection criterion and justification: “occupations involving extensive day-to-day navigation, with often unpredictable, real time navigational demands.”

> All subjects died between Jan 1 2020 (COVID) to Dec 31, 2022.

> There was no data on duration between active employment in listed employment categories and age of death.

This study is a formalization of existing outlier data, that many people associate with Alz resistance. This is basically anecdata.

How confident do you have to be to make a comment like this? Not only point out a problem, but make a snarky comment about the larger system in top of it. What happens to your psyche if you’re wrong? Is the risk of being wrong outweighed by the emotional boost of being right? Did you even consider you might be wrong? I’m genuinely curious

After making a bad comment, don't come back to check replies.

The study doesn't show the same effect for airline pilots, who definitely can't work while having Alzheimer's.

https://www.bmj.com/content/387/bmj-2024-082194

> Very flawed study.

Without a doubt. Borderline useless.

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