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Parachute use to prevent death and major trauma when jumping from aircraft (bmj.com)
370 points by pentestercrab on Dec 14, 2018 | hide | past | favorite | 110 comments

Remember to reard the linked editorial for context: https://blogs.bmj.com/bmj/2018/12/13/we-jumped-from-planes-w...

> We conducted the PARACHUTE trial to illustrate the perils of interpreting trials outside of context. When strong beliefs about the standard of care exist in the community, often only low risk patients are enrolled in a trial, which can unsalvageably bias the results, akin to jumping from an aircraft without a parachute. Assuming that the findings of such a trial are generalisable to the broader population may produce disastrous consequences.

>Before you jump to the conclusion that we’re suggesting we jettison RCTs from clinical research, let us clarify that that is not our intention. In an ideal world, new interventions would always be carefully evaluated through rigorous RCTs before widespread adoption. But when pre-existing convictions about an untested intervention affect the population enrolled, even a well conducted RCT can provide misleading results. Without careful attention to context, extrapolating findings from such an RCT to the patient in front of us may be, well, a leap too far.

It's also essential to read the first cited article (https://www.bmj.com/content/327/7429/1459?ijkey=3b8c1a70a8d2...) which very much inspired this paper and is also quite a bit funnier.

$37 for 1 day access to download the paper. If that's not part of the satire, I don't know what it is.

That might be the suggested amount, and it is a great paper, but I think you are allowed to donate less if you choose: http://sci-hub.tw/10.1136/bmj.327.7429.1459

Thankfully at least bmj still has a real website. Most of the elsevier journals have moved on to a 'web app' design for journal articles and IEEEXplore has as well. These load and display absolutely no article information until you successfully run all of their third party code (only works in latest Chrome and FF). That means you can't even get the DOI from the page for sci-hub. All you get is the crappy little 'loading' spinners.

You will benefit from http://unpaywall.org/

It's like when someone says something funny, then another person follows up with a witticism that basically repeats the same joke...

Like someone makes an inspired pun and some dude immediately exclaims "LITERALLY!"

The point being made by this new paper is actually substantially different to the original 2003 one

They did an actual trial here though

Also, the one with the trial was just published, while the funny one is from 2003. Maybe this is immediate in sea turtle years?

>We think that everyone might benefit if the most radical protagonists of evidence based medicine organised and participated in a double blind, randomised, placebo controlled, crossover trial of the parachute.


> The relevance to parachute use is that individuals jumping from aircraft without the help of a parachute are likely to have a high prevalence of pre-existing psychiatric morbidity. Individuals who use parachutes are likely to have less psychiatric morbidity and may also differ in key demographic factors, such as income and cigarette use. It follows, therefore, that the apparent protective effect of parachutes may be merely an example of the “healthy cohort” effect.

I've always known the parachute manufacturers mostly ride on fear, uncertainty and doubt on this. They ruthlessly cash in on people's lack of knowledge and fear of death, advertising parachutes as a safer option which people buy because it's like insurance; if you'd happen to fall, you'd at least want to feel having prepared.

So I'm glad to hear there's now some scientific evidence pointing to the futility of parachutes. Surely, the experiments were carried out in a constrained environment with some unavoidable assumptions baked in but it does rather convincingly suggest that parachutes consistently do not offer any help in the event of freefall.

A corollary might appear that parachutes might even do more harm, adding weight to the falling person which could cause further injuries unnecessarily upon touchdown.

I'll look forward to follow-up research.

The big question is how would altitude affect the results.

For experiments at higher altitudes they might need to locate an airstrip situated on a mountain, with enough runway to allow larger planes to land there and enough free space on the tarmac for several planes while they carry out the jumps. It will likely shed much more light and build confidence to the applicability of this new research and the obvious conclusion.

Also, I'd like to see jumps done from different kinds of aeronautic vehicles, by more people, different brands of parachutes etc if should there be any differences regarding that. But it looks like after a few rounds of serious experiments we should quickly conclude the benefits are thin and see no need for excess research but, rather, reaching a steady conclusion.

I suspect that landing on water has no discernible effect on the health of the suspect. And he will be completely soaked, so avoid jumping over water and always try to land on land.

Notably, as to choosing land vs. water when falling from high altitude, see the ever fresh: https://news.ycombinator.com/item?id=11748528

A coworker of mine once made this proposal. 5 of us would start a company. The company would buy key man insurance for everyone, then go on a company team building trip. On this trip, we'd all skydive, but one of the 5 parachutes would be non-functional...Profit!

This coworker of mine soon after left the company by storming out of the meeting room and slamming the door, then took up playing online poker for a living.

There's a short term group loaning 'game' in Cambodia called and based on Tontine, which I would guess comes from the French influence.

The game is played by groups who agree on a monthly stake. Each month players offer an interest rate they're willing to pay (more like a tax), the highest rate is awarded the collective pot, less the interest which is redistributed to the other 'living' players.

Players who have already received the pot are 'dead' and do not collect their share of interest in future rounds (meaning they must pay the full stake). Once everyone is dead, the game ends. Some will have come out ahead, others may have been able to get a lump of cash when they needed it

Also in Thailand and Laos. These games are hugely popular. Called a "share" in Thailand and "houay" in Laos.

It's some basic banking services for the unbanked in essence.

How is it prevented that they get "stuck" because no participant needs the money right now and would rather wait and see if someone else is willing to pay an interest?

Maybe I'm misunderstanding, but how is this different than a pyramid scheme?

From my understanding, there's nobody added on while it is running, but a fixed group from start to finish.

My first introduction to this concept was through the wonderful https://www.imdb.com/title/tt0061204/ (The Wrong Box). Highly recommended.

It would be pretty interesting to make an Ethereum based Tontine system

Oh it's been done https://tontinetrust.com/

That's awesome, thanks! So is this: https://tontine.com/

Still popular in France, in 1906 they fell out of favour in the US due to the insurance company issuers tampering with the membership ledgers & then withdrawing too much investor capital as "insurer profits".

Some things never change.

I can't tell, is that a real site or a joke?

It has to be a joke as it is illegal in the US.

Edit: Upon further reading, seems like someone is actively trying to make this happen.


Anyone else get acquainted with tontine from the simpsons? I watched that episode as a kid and still remember it to this day.

I learned about them from a MASH episode in which Colonel Potter was the last surviving member of a WW1 tontine.

No, The Butt by Will Self.

Key man insurance policies explicitly exclude parachute jumps.

I know because one of the founders of the company I work for used to jump, and he had to give up his hobby for that reason.

I think you'll find that key-man insurance policies contain clauses explicitly to prohibit these sorts of shenanigans.

I guess that was around 2005? What does he do now?

The crypto boom really took me back to that time. Suddenly everybody was a poker expert and nobody ever spoke about their losses. Friend of mine made 120k lucking out on a tilt and then lost it all before paying any of the required taxes. (In some countries he could deduct the losses, but here he couldn't.)

This isn't just for giggles. It's evidence that when there's a high perceived risk, "normal" people don't sign up for trials and it skews the results.

> The study also has several limitations. First and most importantly, our findings might not be generalizable to the use of parachutes in aircraft traveling at a higher altitude or velocity. Consideration could be made to conduct additional randomized clinical trials in these higher risk settings. However, previous theoretical work supporting the use of parachutes could reduce the feasibility of enrolling participants in such studies.16

> 16. Newton SI. Law of Universal Gravitation.Philosophiæ Naturalis Principia Mathematica, 1687.

>Compared with individuals screened but not enrolled, participants included in the study were on aircraft at significantly lower altitude (mean of 0.6 m for participants v mean of 9146 m for non-participants; P<0.001) and lower velocity (mean of 0 km/h v mean of 800 km/h; P<0.001).

This is an amusing didactic example of how the "fine print" can invalidate a study's conclusion.

In case anyone else got curious about parachuting injury statistics, Google found me this (also cited by the article):

"Parachuting injuries: a study of 110,000 sports jumps", 1987, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1478603/

All 6 deaths they observed, were either failures to activate the parachute (4 cases), or parachute malfunction (2 cases).

> PArticipation in RAndomized trials Compromised by widely Held beliefs aboUt lack of Treatment Equipoise (PARACHUTE)

That has got to be one of the most torturous acronyms I've ever seen. That's a bit of a stretch.

Oh my sweet summer child...

Biomedicine has gone whole hog into torturing acronyms to make useful sounding cohort names.

Also NASA. They just landed InSight on Mars. Interior Exploration using Seismic Investigations, Geodesy and Heat Transport.

Most of the names are something where they're clearly trying to squeeze out a cute cohort name at all costs.

Would you indicate this is a satirical article? Half the time I was looking for jump height or understanding if adding parachutes to commercial aircraft that suddenly experienced breakage such as a missile would improve passenger survival.

The fact that this isn't immediately tagged as satirical and requires actually reading the article and fully understanding the context (rather than just reading the headline and making a quick assumption) is pretty much the entire point of the "study" and the authors of it. Marking it as satirical would sabotage the purpose.

Indeed, this is half the point of the BMJ Christmas Issue, which happens every year.

Yeah, tried reading the summary and then the first few comments and I was still confused about what the heck they were talking about.

Anecdotally I find the slow realization that something is satire to be an integral part of it's entertainment value.

That was, after all, how something like A Modest Proposal was structured. You were supposed to believe the author was serious at first. That's an important element to a lot of satire.

I've done over 900 jumps so I can fill you in, no references ATM because I'm on my phone.

If you jump with a parachute, you will see chance of death go from 0% at zero feet, to approximately 100% at 35 feet. From there, it will remain near 100% until you reach about 600 feet, which is about the minimum distance it takes a parachute to open. Above 1000 feet and chance of death floors out near 0%

35 ft is a little pessimistic, the LD50 is 10.5m (~35 ft) for those with head and chest injuries, and 22.4m (~75 ft) for those without. Which is surprisingly far.

In patients with head and chest injuries, a 50% mortality rate was estimated to occur at falls from 10.5m, compared to 22.4m in those without injuries to head or chest


Studies like this don't provide good data points for "if you jump[...]" as the GP mentioned. The data is gathered from people who either accidentally fell, or intentionally jumped not intending to live.

They can't just randomly recruit people and have them jump to their near-certain deaths from ever increasing heights due to pesky medical ethics boards.

This matters because a person who's forced to jump from a significant height out of desperation (e.g. to avoid a fire) is likely to take certain precautions that people who accidentally fall don't take, and those trying to kill themselves intentionally avoid.

I distinctly remember seeing a video of a jump my unit did in Honduras (right before I got there) where someone on the ground with a camera followed someone burning-in who opened their reserve at ~50-75ft and "walked" away with just a broken tailbone.

There was another case where someone "successfully" burned-in from 800ft (where we did all our jumps from) and survived because they did a proper landing or, perhaps, just pure luck.

From what I remember there were only a couple jump-related fatalities in the 3 years I was on jump status and the 82nd did something like a million jumps a year...which says a lot because if we went 82 days without a fatality we would get a day off and in 3 years we reached that goal exactly once.

”approximately 100% at 35 feet”

Not sure about that. Although chance of death would be significant, there are many cases of people surviving falls from greater heights.

There are of course extraordinary cases. There is that last tiny fraction of survivors.

But really, falling sucks. There is a reason working in solar is more deadly than working in nuclear. And the reason is occasionally an installer falls off of a roof.

Some people survive such falls but they typically require extensive surgery and long hospital stays. They often suffer serious long-term cognitive or physical deficits. It's not a fun way to survive.

99.9% is approximately 100% ;) But yeah, that's a number I just pulled out of...thin air.

Will jumping from high enough without a parachute ever decrease the odds of death than they the odds of death at a lower altitude?

Theoretically, once you're high enough that you reach terminal velocity, any additional altitude does not increase your speed but does increase your time in the air, potentially giving you more time to navigate towards a more favorable landing site (evergreen grove, mountainside covered in deep snow, pile of 45 mattresses that happens to be outside, etc).

If you're far enough away you'll suffocate before reaching the ground.

Not that I know of. Maybe, if you jump from high enough that you pass out due to lack of oxygen, and you land in a manner that benefits from you being a ragdoll vs an actively bracing person, then it could help, but that seems unlikely(you'd probably also wake back up before you hit the ground, as I've heard stories about this happening to WWII pilots).

But overall, I believe it is better to be conscious. If you are falling from 3 miles up, you can glide to maybe 1 mile in any direction. This gives you the chance to try to land in a snow drift, in some mud, maybe a hay bail, or even a thick shrubbery, etc.

First you must find... another shrubbery! Then, when you have found the shrubbery, you must place it here, beside this shrubbery, only slightly higher so you get a two layer effect with a little path running down the middle. ("A path! A path!") Then, you must cut down the mightiest tree in the forrest... with... a herring!

Not for humans. You're thinking of cats.


This is almost certainly survivorship bias[1]. Only middle-height cats that might theoretically survive are going to be taken to a veterinarian; the cats that fell from higher heights were not included, because they were "obviously dead". Which makes "high-rise syndrome" an example of the exact type of bias discussed in this paper.

[1] https://en.wikipedia.org/wiki/Survivorship_bias#In_cats

> Strangely, cats that fall from a height under 6 stories have more severe trauma than those that fall from over 6 stories.

So, the theory is, if a cat falls from a height above 6 stories they either have less severe injuries or are just dead so the owner just doesn't bring them to the vet?

>>6 stories they either have less severe injuries or are just dead so the owner just doesn't bring them to the vet

I would guess that at that height something must've broken the fall such that the cat suffered almost no injuries. I really don't see how the cat would survive the fall otherwise.

Cats are much smaller than humans and better prepared to absorb impact after "floating" to ground. I assume breaking the fall would actually be dangerous to cats because it disturbs their approach.

There is obviously an element of satire, but are the authors are also trying to make some sort of statement about clinical trials?

Clinical medicine, especially, is often paralyzed by "We don't have an RCT about this particular circumstance therefore we know nothing."

This article is making a comment about that.

Yes. Consider trialling a new drug that is supposed to prevent/cure a terrible disease, and has a well explained mechanism of effect, supported by clinical results of some % of sick people no longer being sick after treatment.

If you want an RCT you need a control group who will be subjected to the horrible disease with standard treatment (and sometimes a group with no treatment), and a group subject to the experimental treatment. Who will volunteer for this trial? Perfectly health people? Or people with the disease?

Like, maybe the measles vaccine is all just placebo effect and good sanitation and handwashing practices. Can we do an RCT where we inject some children with saline instead of vaccine, then see what happens?

Because we can't be certain the children of crunchy hipsters who don't get immunised get measles is related to lack of immunisation, it might be they expose themselves to exotic strains by taking exotic holidays.

Isn't satire always trying to make a serious statement? Or at least, good satire?

Jump height is even in the abstract. You have to read it though, skimming won't work.

"The PARACHUTE trial satirically highlights some of the limitations of randomized controlled trials."

Anyone know if these results have been reproduced by anyone? I'm a bit skeptical.

Assuming you’re serious, you can reproduce this yourself. Put on a backpack, stand on a chair and step off. The trial participants “jumped” from 0.6 meters.

I wonder if they where gunning for an Ig Nobel Prize. I'm sure they'll be nominated.

They were submitting to the BMJ Christmas Issue, which is an excellent read every year. Usually a bit of satire and humor mixed in with interesting methods.

> A key strength of the PARACHUTE trial was that it was designed and initially powered to detect differences in the combination of death and major traumatic injury. Although the use of softer endpoints, such as levels of fear before and after jumping, or its surrogates, such as loss of urinary continence, could have yielded more power to detect an effect of parachutes, we believe that that our selection of bias-resistant endpoints that are meaningful to all patients increases the clinical relevance of the trial.

I love how much detail into which they go.

But not a placebo-controlled one? Shame.

Their methodology has some serious shortfalls ;)

I think this is like the medical research paper version of the famous RFC for IP over Avian Carriers.



> The PARACHUTE trial satirically highlights some of the limitations of randomized controlled trials. Nevertheless, we believe that such trials remain the gold standard for the evaluation of most new treatments. The PARACHUTE trial does suggest, however, that their accurate interpretation requires more than a cursory reading of the abstract. Rather, interpretation requires a complete and critical appraisal of the study.

I love this paper. Whenever you see pop news articles saying "Study shows X is good/bad for you," if you dig in to the paper, it's often something like this. When you read the specific details, you realize the study doesn't generalize to "You should/shouldn't do X." But not enough people read the details, so it gets circulated into conventional wisdom :(

Must have been a fun IRB approval process. Wish we could also see those applications/disclosures!

>Ethical approval: This research has the ethical approval of the Institutional Review Board of the Beth Israel Deaconess Medical Center (protocol no 2018P000441).

I know this is a boring response, but I feel like there’s a formalism here to consider why a RCT would be “obvious.”

Let’s say you’re going to use some causal model, like a regression adjustment technique. You could for example assign people to the treatment group (receives parachutes) and the control (no parachutes), and then observe who lives and dies, as well as a bunch of potential confounders like altitude, age, fitness, whatever.

Fit a logistic regression to predict the outcome (survival) based on the treatment (parachute) controlling for the other characteristics. Then read off some effect size and ststistical significance.

Or better yet, and here’s the important part, you could make it a Bayesian logistic regression by considering prior distributions for the regression model’s fitted coefficients, and sampling draws from the posterior distribution of coefficients using the data set and your priors.

So what is the prior on the coefficient for the treatment term (parachutes)? Well, probably pretty damn high. Definitely some strongly informative prior, take your pick of historical data or effectiveness rates of physical safety equipment, whatever.

From this prior, and making some neutral assumptions via the priors on other weights, you could figure of what the effective sample size would be for a data set to disconfirm your prior (e.g. a posterior with a mode on the parachute coefficient far away from your strong prior). Sort of like a power analysis, but assuming a fake data set that shows nothing but failed parachutes. How much of that silly data would you need based on your prior?

What this would tell you is that you’d need some insane, physically ludicrous amount of data that flies in the face of an obvious prior, that what would be the point of running the study? You’re just going to confirm your prior.

So the real question is how often is this a realistic description of other situations when you want to study a treatment?

That’s the thing, right? That the author kind of wants to be snarky about.

But really, it’s pretty fair to say you don’t have such a strong prior that the study would be futile, even in cases when you sort of do feel like the conclusion is obvious (e.g. taking Tylenol leads to less pain, college kids prefer drinking instead of homework). While it passes some gut test of what’s obvious, that’s different from really betting on such a one-sided prior that a study is futile.

To me it suggests most of the sort of “duh” RCTs carried out are pretty much fine. Whether or not the study is worth it or is informative would be based on other priorities like cost, licensing or certification requirements, whether it’s of value to specialists who care about splitting hairs on accurate effect size measurement, etc.

It's not actually an argument against "duh" RCTs.

It's an argument against clinical medicine being fixated on RCTs as the one-and-only form of evidence that can be taken seriously, even when - as you note - the Bayesian prior for such a situation is extremely high.

This happens more often in the field than many people might think.

N=92 participants is not big enough of an N to conclude anything. To see differences you're going to have to go up to 10 times more at least.

I'd hate to be part of the control group.

When can we expect a news article telling people scientists advise not to wear parachutes?

Some comments have touched on a few of these points but I’ll try to bring them together. So first, yes the headline is a joke (BMJ Xmas has satirical content), but it also has a history beyond the immediate point of the paper—that sometimes RCTs can’t accrue properly to a control arm to fairly evaluate an intervention.

Quick points:

   - There’s a history to this analogy and paper within
     biomedicine and this journal (BMJ) from a 2003 article,
     which I’ll get to.

   - Parachutes are a dangerous metaphor in medicine, 
     where almost nothing has an absolute risk reduction 
     of >99% (note: not 100% because, yes, a handful 
     of people have survived falling from altitude without 
     a parachute), especially over the time-frame 
     of a matter of hours.

   - This should not be a call to stop attempting RCTs 
    (which is the conclusion some commenters have made), 
    but an exhortation to find ways to create better ones 
    when conditions are challenging. Frequently, objections 
    to doing an RCT because “how could we withhold X 
    from the control arm!”, are not as obvious once 
    the data are in.
Some background: beyond Retraction Watch looking for outright fraud, there’s a movement toward opening trial data for analysis because abuses in RCT design/analysis/reporting have gotten more criticism and attention lately. This is happening at the same time as the FDA has been moving toward lower/faster evidentiary standards for approval (see Sarepta controversy and general guidance in 21st Century Cures Act to allow drugs to market with earlier phase evidence and based on “surrogates” like was the tumor 2in vs 3in bigger vs hard endpoints like “did this person die later than the control”), so it couldn’t come at a better time.

The broader point is that the 2003 “parachute” article in the same journal (BMJ), was frequently incorrectly understood / used.

While “parachutes” makes an easily understandable headline, it is almost totally unrelated to the field of medicine where we rarely have a shot at doing something as obviously lifesaving as making someone hit the ground at 10 mph vs 120 mph. The problem is that people have cited the 2003 paper mentioned in the thread to justify a number of interventions that ended up not being better than prior care. The interventions were started in good faith because was “obvious” to their creators that doing X would be helpful (spoiler: it usually wasn’t or wasn’t that beneficial).

A lot of this is cribbed from Vinay Prasad, who has a twitter thread about this: https://twitter.com/VPplenarysesh/status/1073298754298556416

He is a controversial figure, but I think he does a good job of hammering home some important skepticism about a great deal of medical literature and practice to a broad audience.

I’d appreciate hearing objections to the above, btw.

Please fix the title. It's misleading. The linked article in no way claims that "Parachutes prevent death when jumping from aircraft".

Given that it says "randomised trial", it's implied that there would be a control group — a group of people who are sent to die for the sake of an experiment.

Given that nobody would ever do this, it's quite obvious that there's some tongue-in-cheek angle to the story.

It isn't misleading if you can read between the lines.

To the contrary, I think it might be you who is jumping to unfounded conclusions. Contrast the current title "Parachutes prevent death when jumping from aircraft: randomized controlled trial" with the first line of from the Conclusion of the paper: "Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention".

The finding was that parachutes have no effect on deaths. Title is the exact opposite of the finding.

Well, maybe it does if you correct for the obvious errors in the statistical analysis. How did this get through peer review? I was particularly bothered by this sentence: "A P value greater than 0.05 was statistically significant."

Presumably they meant "less than", but it's hard to trust any of their conclusions with such sloppy attention to detail.

It's satire: "The PARACHUTE trial satirically highlights some of the limitations of randomized controlled trials."

The current title "Parachutes prevent death when jumping from aircraft: randomized controlled trial" is exactly the opposite of the article's conclusion: "Parachute use did not significantly reduce death or major injury (0% for parachute v 0% for control; P>0.9)." Nor is it the title of the actual article.

Why do people use parachutes then? I felt like I'd like to have a parachute jump experience one day, do you mean that would equal jumping without a parachute (guaranteed death)?

The trial is essentially a joke. Here's some more context:

> participants included in the study were on aircraft at significantly lower altitude (mean of 0.6 m for participants v mean of 9146 m for non-participants; P<0.001) and lower velocity (mean of 0 km/h v mean of 800 km/h; P<0.001).

So essentially they had people jump about 2 feet from an airplane sitting at rest. Of course there were no injuries, and that was the point. Few people will participate in a trial in which the control group could die, and such a trial would be highly unethical.

It’s not guaranteed, there’s numerous cases where someone’s parachute malfunctions and they land with only broken bones and bruises.

I know but I have chosen to simplify the idea as the chance to survive (and recover your health to the level at which you won't regret you have survived) is negligibly small.

The current title serves the point of the article quite well.

This title has been editorialized from

"Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial"


"Parachutes prevent death when jumping from aircraft: randomized controlled trial"

I believe that's an extremely subtle meta-joke on how popularizations of clinical trials always manage to mis-state what can actually be concluded from the trial. If so, well done. If that wasn't an intentional joke, even better.

It would suck to be in the control group. ;)

Also, as my grandfather was a paratrooper: parachuting isn't a risk free activity even when the main canopy deploys properly, i.e., broken limbs on landing. And it's remotely possible to survive a fall without a parachute from terminal velocity height, i.e., Vesna Vulović. Edit: <- Edge-cases contrary to the obvious.

The control group in this study only fell a couple of feet at most. I don't think it sucked much for them at all.

Smh. Poe's law disclaimer wink added.

Ha! Fair enough. I'm leaving my comment just in case other people really do misinterpret the study.

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