Comment by cortic

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

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?

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.

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?

First time on HN?

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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.

This is mentioned in the article as well.

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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.

Collecting a bunch of covariates is never a substitute for recognizing that you can't force people to be taxi drivers for life.

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.

Learning new languages (and actually using them) is a great way to do this for all ages!

> 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.

> CBA to look at the article

then don't post

BASE jumpers and wing suit fliers too.

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

> "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/

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.

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.

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.

That's like, almost all of them.

survivorship bias

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."

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.

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.

>For from the look of it it doesn't look like an exceptionally hard job

Define "hard job". Carrying heavy objects?

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.

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"

He was method acting, so I'll allow it.