Taxi Drivers: The mean age at death is approximately 67.8 years.
General Population: in the same dataset, life expectancy averaged 74 years.
The average age at which patients are typically diagnosed with Alzheimer's disease is 79.
People in these jobs don't live long enough on average to get diagnosed, at the same rate. The same effect will happen in any job that lowers your life expectancy.
It pains me to see such a low-effort contrarian comment at the top: as stated in TFA taxi drivers are below other profession when controlling for age, and there are multiple professions with lower life expectancy that still have significantly higher Alzheimer rate than taxi drivers.
Fella has read the article, has an argument and some stats. What more do you want from a comment? He isn't running a study.
Besides, the point is a good one. There are a lot of professions. If we glance at the underlying study [0] Figure 1 suggests that we'd probably expect to see an outlier or two in that mess just through chance, we're expecting a few p<0.01. Taxi drivers doing unusually well doesn't seem especially impressive in that light, especially since it is one of the professions that seem to die off rather young and we might expect one of those professions to do rather well on Alzheimers.
[0] https://www.bmj.com/content/387/bmj-2024-082194
The comment insinuates that the study did not control for age. The study controlled for age.
It's not terrible to not make a good point, but it's not a good point. The not good points should not be ranked highly.
But after the study controls for age the starkness of the effect more or less disappears (eyeballing Fig 1, the 2nd graph).
It turns out that there is a profession with a lowest risk of getting Alzheimer's (duh, one had to exist) and it looks like a slight outlier (it's the lowest, we'd expect that one to look like a slight outlier). As outliers go it isn't that impressive, it looks like it is part of a fairly boring distribution. We just plotted 400 data points on the graph, the 1/400 chance weird data point is going to look a little weird. We're actually just reading a lot into the fact that the 2nd data point in ambulance drivers which isn't all that convincing.
Not to knock the study, I'm sure it is a great study. Lots of science done. They do good graphs and all that. But the study appears to be telling me that Alzheimer's is random with respect to occupation and ideally don't spend so much time on the road if you want to live to see old age.
A distinction is that Alzheimer's is in an uncommon category of mystery diseases.
If a study found people who swim regularly are are less likely to get heart disease, that wouldn't be very surprising because know a lot about why people get heart disease. Therefore it would be valid to insist on more rigour for accepting (swimming => less heart disease) because the only use of that information is for health advice.
However even weak statistical correlations can be a valid lead for further research into Alzheimer's disease if they suggest where to look. You don't need to prove that signposts are correct in order to use them.
True. But, these are still odd outliers in terms of low life expectancy, and that's something that the actual BMJ article cited (https://www.bmj.com/content/387/bmj-2024-082194) or TFA talks about at all. The LE is low enough for both professions to be awkward.
I'm also a little concerned that the BMJ plot of risk adjusted mortality still shows a clear positive correlation with age at death, which I strongly suspect would turn out to be statistically significant. The adjustment does not appear to be correct, therefore, and while that might still preserve these odd findings, it's definitely not ideal.
The much better occupation, from the graph, is the third outlier -- mining and geological engineers. Life expectancy: 80.3, risk-adjusted mortality: 1.1%. Or, alternatively, economists are close too (80.6; 1.19%).
Aircraft pilots, btw, really were the opposite end of the scale (78.1; 2.3%), surprising enough to be noteworthy beyond a control (the BMJ article does discuss this a little, but seriously -- that's very surprising for a highly-educated profession).
A better low effort contrarian comment - isn't it that early symptoms appear less often with people with a "reserve"?
Being mentally active (or physically active?) IIRC makes actual plaques both less likely, but also less detectable - a taxi driver can forget 90% of what they know and still not get diagnosed because they don't get lost on the way to the shops. Also they are often masters of small talk.
Just the top one?
Every top-level thread is like a multiple choice armchair takedown.
Here's an interesting counterpoint. "Unthinkable" presented studies of navigation tasks in 2D/3D and testing/training. Hippocampus measurements correlated with skill and training. Interestingly, this skill and training and measurements all correlated with beneficial responses in a disaster (as in, not panicking). Weird right?
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I do wonder if you can truly control for it in this case, or if doing so doesn't in and of itself introduce a survivar bias that masks a reversal of causality. That is: could the taxi drivers who are already predisposed to have a lower chance of developing Alzheimer for other reasons also be the ones who are more likely to live to be older than the average taxi driver?
But on some level I understand the immediate low level criticism. Of course, it’s stupid to criticize something without reading about it. However, I’ve seen waaaay more studies which was made with even lower effort.
For example, the other day I wanted to figure out what’s the current state about whether gender equality causes measurable benefits for companies… and the studies are terrible. All of them. Most of them was about Norway, and almost all of them had a reference point in 2008, one of the largest economic crisis, and somehow most of them was even worse than this. They openly distorted statistics. Depending on what they wanted to achieve to one way or another. Even the most cited ones. It’s disgusting. The best ones could prove only that inequality is not inherent of economics, but social. But the agenda was different for them too, so they tried to lie something bigger, all the time, while this would be more than enough to support it.
First time on HN?
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And how would you control for the causal possibility that those who will eventually develop Alzheimer's early on might tend to have undetectable memory issues that prevent them from becoming taxi drivers in the first place? You can't control for profession, since that's behind the very claim itself.
Its even worse than that, i can imagine people with undiagnosed early Alzheimer's self selecting for car accidents and cardiac issues through additional stress of mental fatigue while their brain tried to compensate for loss of function.
So you have people self selecting out of the profession, self selecting for early death within the profession, and on top of that, a general life expectancy discrepancy that is near impossible to adjust for.
What happens in the age of self driving cars?
Fewer car accident deaths, leading to more elderly people, which inevitably means a higher population of people with Alzheimers.
(Unless people highly predisposed to dying in car accidents are also highly predisposed to mudering people who will have, but don’t yet have, Alzheimers. But that seems sufficiently unlikely for the purposes of this hypothetical.)
Jokes aside, the serious answer depends on whether the link is causative or merely collerative.
At one point the amount of human induced accidents will increase since no human can account for sudden erratic brakes of a self driver, even though it predicted a correct incoming accident with another V2V connected car.
No taxi drivers
This is mentioned in the article as well.
Isn't the mean age simply brought down by the number who die at a very young age due to car accidents, robberies, and other reasons?
Not that cab drivers only live to 67 - many would still live to 75, 85, 95, but that occasionally a driver dies at 25 or 35 bringing the mean figure way down.
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The study accounts for that.
Delay your aging by using your brain a fuck ton, all the time, learning brand new things nowhere near anything you already know.
Alzheimer's is an entirely different beast than normal mental atrophy and there are plenty of stories of otherwise intelligent people ending up with it.
I'm not saying you shouldn't try using your brain more but this is just like saying Stephen Hawking should have tried exercising more.
Would this not be closer to saying Arnold Schwarzenegger should have tried exercising more?
Both Stephen Hawking and Arnold Schwarzenegger would have benefitted from exercising more, if controlled for age
/s
Collecting a bunch of covariates is never a substitute for recognizing that you can't force people to be taxi drivers for life.
However, you might be able to find a natural experiment were taxi drivers were randomly prevented from continuing with their driving career?
Could just be that whatever factor causes certain cabbies to live much longer than their cohort is also protective from Alzheimer’s. I guess they might have accounted for that too — I’ll have to look at the study.
Or, that if you can survive the thing that kills the rest of their cohort, it has beneficial tradeoffs. As in, perhaps smoking protects from Alzheimer's, if it doesn't kill you first.
Controlling for age in a profession with a high fatality rate like this seems like controlling for high alertness, consciousness, quick reaction times, and well restedness/low stress, low recreational drug and alcohol use.
Of those, sleep issues are highly correlated with Alzheimer's and also with auto accidents. Controlling for age alone here would select for low incidence of sleep issues.
Learning new languages (and actually using them) is a great way to do this for all ages!
I'm bilingual. Learning new languages is pointless if you have no one to talk to in the new language.
Language skills atrophy surprisingly fast.
| 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.
They claim to control for these factors in the 5th paragraph of the article here. Which is a standard thing to do in these kind of studies.
So you're point is either not relevant or that they didn't control for age correctly?
Studies typically use regression to account for stuff like that. CBA to look at the article, but I bet any money that's controlled for.
> 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.
So no indication they accounted for the expected lifespan of the profession.
Adjusting for age seems like an indication to me
It’s insufficient. For example, the people who develop Alzheimer’s may for whatever reason may be less likely to survive the profession where Alzheimer’s is the cause of death (eg getting into a fatal car accident where undiagnosed early onset is the problem). Bus drivers typically drive the same route over and over and probably have safer trips overall than taxi and ambulance drivers.
It’s a plausible hypothesis but it’s really really hard to tease things out and controlling for age is the obvious thing but that doesn’t get you the conclusive result you think it does.
Adjusting for sample/population age is the simplest interpretation of that
Indeed. I feel that although many people try to learn new languages, the intellectual stimulation provided by doing so is understated. Especially learning languages very different from your native language (grammatically, morphologically, etc.). It’s almost like finding new ways to think.
Seems like a fair point.
> CBA to look at the article
then don't post
Mate, you ever read a scientific paper? You dig regression? Did you read TFA yourself? Was I wrong?
Yep. Free solo climbers also rarely die of Alzheimer’s.
BASE jumpers and wing suit fliers too.
That's why I make sure to wear a wing suit at least one day a week.
As the paper points out that's accounted for in the analysis, because shockingly enough to most internet commentators researchers know that they need to control for confounding variables
https://www.bmj.com/content/387/bmj-2024-082194
The 1/60 to 1/100 difference could be explained by just one small confounder that is impossible to cover for. Therefore in my opinion making any conclusions based on this study wouldn't be fruitful at all.
Always insane to me how people will just read the headline of an article and point out "flaws" based on what they assume the article says
People jump the gun to show their perceived intellectual superiority. Typically same kind of people are last to admit of a mistake.
It's not necessarily about intellectualism. Science in modern times is plagued by publish or perish. Researchers just need to get things published to keep working, and negative results don't get published. So I think people often publish stuff without proper controls/missing confounding variables/inversion of causality/etc not out of ignorance, but because they know the conclusion is dubious - but if they don't publish, they're going to be out of a job.
I don't think many realize how huge the replication crisis is. You have 75% of studies in a leading social psychology journal failing to replicate. [1] Another replication effort on preclinical medical studies found only 11% were able to be replicated, a replication effort on cancer studies found the average effect size to be 85% lower than published, and much more. If you assume most science headlines, at least outside of the traditional hard sciences, are false - you're substantially more likely to be right than wrong.
[1] - https://en.wikipedia.org/wiki/Replication_crisis#In_psycholo...
> It's not necessarily about intellectualism. Science in modern times is plagued by publish or perish. Researchers just need to get things published to keep working, and negative results don't get published. So I think people often publish stuff without proper controls/missing confounding variables/inversion of causality/etc not out of ignorance, but because they know the conclusion is dubious - but if they don't publish, they're going to be out of a job.
This is very true. In my PhD research, I managed to perfectly predict the placebo effect using a random forest. Now, this was actually due to sampling variance, and the finding went away when I averaged over splits.
I often wonder if I'd still been in academia when this happened, if I would have been able to resist the siren call of a Nature/Science paper (and the consequent career benefits).
And then their comment also reliably becomes the top-voted comment in the post
You actually read the link ?
They got trained to said assumptions by bad sensationalist 'science journalism'. Remember how power lines caused brain damage in children? Not through the magnetic fields or anything like that, but the lowered property values.
> "researchers know that they need to control for confounding variables"
'Why ‟controlling for a variable” doesn't (usually) work' - https://dynomight.net/control/
Other things that don't work, including four other 'controlling for a variable' entries at items 39 through 43: https://dynomight.net/things/
Also https://journals.plos.org/plosone/article?id=10.1371/journal... and https://slatestarcodex.com/2014/04/26/stop-confounding-yours...
They are likely studying individuals that retired without getting fatally stabbed or shot on the job.
It's not violence from the job but their job was generally bad for their health in other ways. Sitting all day without getting up and driving around with windows down getting all this UV.
Also, older ones were exposed to a ton of cigarette smoke.
Also road accidents.
I could imagine taxi drivers have fewer fatal/grave road accidents than the average person or at most slightly more. They tend to drive in cities, are more trained, can't drink or do drugs on the job. For London only 1 taxi driver has died in a traffic accident since 2020.
If you drive more you are more likely to be in an accident, that's just how roads and accidents work.
Sure they might be better and per unit of time they drive they must have miniscule amount of accidents.
But if there's a 0.001% chance per hour driven, then over enough hours a few accidents are inevitable.
They don't just add more hours of driving they replace a small amount of risky hours for a lot of hours of low risk if they change location/job.
Also Drivers are generally less likely to die in accidents in urban areas, on high ways it's different.
Pedestrians are a lot more at risk. So that's unsurprising that annually 1/2 taxi driver might be fatally injured in one.
But I would assume the ratio of other drivers to taxi drivers would be high enough that this number should be zero as well.
I'm gonna go out on a limb and say that not even a double digit percentage of taxi drivers' careers are ended due to violent attacks. Taxi driver doesn't even appear in the U.S. Bureau of Labor Statistics top 20 most dangerous jobs.
> not even a double digit percentage
That's actually crazy if that's as low as you dare guess. I would have easily guessed it was like, a fraction of a percent. 1 in 10 would be fucking nuts.
That's like, almost all of them.
survivorship bias
" (...) 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."
Yep.
"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."
>People in these jobs don't live long enough on average to get diagnosed
not to mention the other devil in these studies: some professions are statistically going to have the lowest rate of every possible disease. you can't just cherrypick outliers and declare "causal!"
>Taxi Drivers: The mean age at death is approximately 67.8 years.
Where? What country/ies?
In the US, but you’d likely see a similar effect in other places. Taxi drivers are highly sedentary and occupationally exposed to a lot more road pollution than most jobs.
That's very interesting but why do taxi drivers have a job that lowers life expectancy? Is it because they're sitting too much? Or because they're inhaling CO from cars too much? Or staying inside (the car) too much? Or is it just stressful?
For from the look of it it doesn't look like an exceptionally hard job (btw a brother of mine did years of "VTC": "Vehicule de Tourisme avec Chauffeur", basically high-end taxis without the "taxi" logo).
I did it, briefly, twenty-some years ago. Lousy job—sitting all day, irregular pay, danger, nasty fares, drunk fares, belligerent fares, fares who seem to have nothing better to do with their days than to find ways to cheat a driver. But the thing that really sucks is the hours: shifts are twelve hours long, either ending or beginning at 3:00am, and because your rental for the cab is highest at the beginning of your work week, descending every successive day (free on day seven), the compensation is structured so that you're making good money only by working a ton of hours.
Because it doesn't pay very well. Being affluent increases life expectancy.
1. They are hardly in the bottom quintile, where the income effect is large enough that it could actually shave 7 years off their life. I'd expect nightly work, irregular sleep patterns, too much fast food and maybe a higher frequency of smoking to do their part.
2. The original study didn't just study taxi drivers, but also ambulance drivers. I doubt that their life expectancy is that much lower.
They are if you consider the amount of hours they work
>For from the look of it it doesn't look like an exceptionally hard job
Define "hard job". Carrying heavy objects?
Stressful on the body.
Odd hours, sitting too much, inhaling too many exhaust fumes, having people yell at you if _they're_ late.
Sounds like a fairly hard job.
Yes, taxi driving can be hard.
There are jobs stressful on the mind too - and some of them have very low "life expectancies".
Lower income, little physical mobility in their job, constantly breathing traffic fumes, and tire and brake dust would be my first suspects.
It’s a very sedentary job, pretty much by definition.
Getting stabbed in the neck by filthy street urchins.
Probably not smart to post something like this on the same message board you’re using to get a job
A joke?
might turn out that the next company they apply to is run by street urchins who don't take too kindly to the stereotype? or possibly humorless scolds who don't want their employees telling jokes in their free time?
did you read the study
Ah, the typical cheap HN reaction to a paper, along with "correlation is not causation", and as usual, for things already factored in into it.
Hilarious, because accounting for this stuff is drilled into your head when you study the softer sciences (like psychology) even as an undergrad.
Next up: "I didn't do a statistical analysis but the sample size seems small"
... in mice!
De Niro is 82, no Alzheimer's. /s
He was method acting, so I'll allow it.
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