An interactive data journalism piece exploring the rise of young-onset colorectal cancer, with population simulations, risk factors, and prevention information.
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By epistasis 2026-02-1923:55 Excellent science communication, as would be expected from this author.
A recent finding from last year looked at the mutational signatures in colon cancer in those under 50:
https://www.nature.com/articles/s41586-025-09025-8
The different processes that damage DNA have sequence preferences for the direct change in the DNA (e.g. G-->C versus G-->T), as well as the sequence around the damage. Smoking causes very very different signatures of DNA damage than, say, damage from UV from being in the sun.
So every cell in our body carries with it a (noisy) history of the mutagenic processes it has been exposed to.
This paper found some differences in these mutational signatures of later colon cancers, and attributed them to colibactin, a mutagen produced by bacteria.
It remains to be seen what percentage of the increase in under-50 colon cancers this would explain, but it's an additional risk factor that didn't make it onto the chart, likely because it's not coming from standard epidemiological analysis, and instead from the world of molecular analysis.
Wow, I had no idea there is a 15X increase for endurance athletes. Make me want to dial down the running a bit, which make you wonder where the sweet spot is for distance training.
It's rare but can happen where long distance running causes ischemic colitis which is where on a long run enough blood is diverted from the large intestine that it damages the intestine long term. It isn't surprising to me that there's higher likelihood of colon cancer given this. It seems like repeated bouts of lower blood for the intestine on long runs has a cumulative impact and damages the colon even if it doesn't cause ischemic colitis.
By sigmoid10 2026-02-1922:33 This theory has been put forward, but it's important to point out that there is no real evidence yet. An alternative theory is diet, which is also the leading theory for increasing incidences in non-athletes. Highly processed, calorie dense foods have been on the watchlist for a while, and ultra endurance athletes have a special need for these to satisfy their caloric requirements. It could also be a combination of these factors or something else that was missed entirely so far.
I wonder if it's due to diet. Endurance athletes love their simple carbs, highly processed gels. I've seen plenty of cyclists taking gummy bears on rides for fuel, or a concoction that is effectively sugar water to drink
The study referenced is really light on details and they don't say if they controlled for that
By xaldir 2026-02-209:48 I was thinking the same thing.
Simple sugars and highly processed foods tends to affect the gut microbiome.
I guess "more ressearch is needed".
By PenguinCoder 2026-02-1922:322 reply Interesting, I wasn't aware of that connection either. I was diagnosed with stage IV colon cancer, but was identified as 'genetic' and not caused by diet or lifestyle. I used to be a heavy runner too, done a few marathons, and plenty more 10k, 8ks etc. Wonder if that could be a correlation... Treatments have it contained/in maintenance so at least I have that going for me.
I too was diagnosed with stage 2 rectal cancer, but it was back in 2005. How did they determine your cause was genetic?
By PenguinCoder 2026-02-201:031 reply Did the genetic genome tests from the biopsy, from a third party company. Helped guide the treatments.
By greedo 2026-02-201:51 Ah, that definitely wasn't offered to me as an option. Glad to see the progress however. It would be nice if there was an alternative test so that I could tell my kids it's not genetic.
By javiramos 2026-02-203:15 Best of luck with your treatment.
By francisofascii 2026-02-200:04 I have an ultra-runner friend who just got diagnosed with stage 4 colon cancer. Absolutely devastating. He had a colonoscopy just a few years ago. His only symptom was not feeling well after a long race.
By parl_match 2026-02-1920:453 reply It may be the damage of repetitive motion, it may be chemicals released into the bloodstream from endurance athletics. It may be something else. Without knowing the root cause, it's impossible to figure out the "sweet spot"
Could be a lot of things. Lots of long distance runners consume a lot of sugary gels to keep going. Not sure what the typical composition is, but likely lots of glucose and no fibre.
The marathon runners I know also seem to eat tons of junk food, they can get away with it from a weight perspective because a long run will burn it off, but it could have other consequences.
Point being: there's a lot about long distance runners that's quite different from other people.
By reenorap 2026-02-200:38 But the rates of obese people who presumably consume a lot of sugars and carbs are 1/10th the rate of ultra marathon runners. It's scary to think that such conditioned athletes could be subject to this horrible disease.
i saw something recently that pointed to the fact that ultra runners end up with less blood in their guts while running for SO long its leading to cancers and such.
By porknubbins 2026-02-203:33 This makes the most sense to me. I wonder how long distance cycling compares given that they can go for even longer than runners.
By reducesuffering 2026-02-1920:532 reply It's not simply endurance athletes though. It was 2x ultra-marathons >26 miles, or at least 5 marathons completed.
By owenversteeg 2026-02-1922:22 >2x ultra-marathons >26 miles, or at least 5 marathons completed
Yes, and it seems like it's really a 7.5x risk increase. Still pretty spectacular, though!
I really wonder what could cause that. Randomly throwing out possible causes: 1) blood redirected away from gut, 2) overuse of NSAIDS, 3) ultraprocessed foods (gels etc), 4) strange microbiome issues (gels + stress in gut from extreme exertion = altered gut flora?)
The study that found the result is DOI: 10.1200/JCO.2025.43.16_suppl.3619
Which is way more than what original hunters and gatherers ever clock. They do move a lot, but not so much, and they alternate their activities a lot too (running, walking, resting, taking entire days off and just guarding their village).
We're not really optimized for this sort of extreme endurance and long-term development of serious pathologies is unsuprising.
By greygoo222 2026-02-1921:511 reply You shouldn't so offhandedly assume a hunter-gatherer lifestyle couldn't lead to issues like increased risk of CRC, or that activities which lead to increased risk of CRC couldn't be what hunter-gatherers did. Evolution is neither fast nor perfectly precise. Plenty of animal populations have common health problems that simply weren't harmful enough to reproduction to be selected out, much less something rare and late-onset like CRC.
I don't assume anything. From what we know about health of the last surviving hunter-gatherers, they suffer significantly less from "diseases of civilization" when taken in proportion to their settled neighbours. Some of those diseases (such as high blood pressure or diabetes 2nd type) seem to be totally absent in them. Cancers do happen, but not as often.
This pattern is quite old. Already ancient Egyptians suffered from civilizational diseases much more than hunter-gatherers, especially the richer ones (heart attacks, gout, cancer).
By greygoo222 2026-02-1922:142 reply I won't bother checking or disputing the accuracy of your factual claims, because it does not matter.
Colorectal cancer is not the same thing as high blood pressure, or type 2 diabetes, or any other cancer that isn't colorectal cancer. Diseases are not a monolith and you cannot assume low risk of some diseases means low risk of others. That is wild guesswork passed off as logic, like measuring the shadow your testicles cast on the wall and announcing it is 24.1 degrees Celsius. Ultra-marathon runners also have low risk of type 2 diabetes!
Do you have specific evidence that modern hunter-gatherers have low rates of colorectal cancer that cannot be explained by survivorship bias, screening, genetic differences, and all other confounders, and that they are representative of historical hunter-gatherers? No? Then you cannot confidently conclude that hunter-gatherers didn't experience elevated rates of CRC.
By pfannkuchen 2026-02-1922:23 Absolutely, we may have a depressed rate of CRC where ultramarathoners just get back up to the historical baseline. Who knows, but we don’t know it isn’t that.
"Diseases are not a monolith and you cannot assume low risk of some diseases means low risk of others. That is wild guesswork passed off as logic..."
Diseases are not a monolith, but they do tend to arise and fall in some specific clusters, and that is not "logic", good or bad (too many computer-minded people drag logic into the chaos that is biology), but rather a long-time empirical observation, albeit with some exceptions.
By greygoo222 2026-02-200:291 reply Your testicles, empirically, shrink when it gets cold. Do you think measuring their shadow is an acceptable substitute for a thermometer?
By inglor_cz 2026-02-209:31 You are really obsessed with my testicles. That is a weird comparison, but at least you know that you're not a bot. This would be too weird for a LLM to produce.
In general, I don't think your irony is as strong as you think. Shrinkage of various materials in the cold is the original basis for a thermometer.
Of course it is better to use something better-observable like mercury. But in absence of an industrial civilization, you don't have mercury to measure.
By greygoo222 2026-02-200:231 reply Sigh. Sure, if you had a gun to your head and you knew nothing else, it would be better to guess that a given population (hunter-gatherers) with low rates of some illnesses (T2D, HBP) also had low rates of another illness (CRC) than the reverse. Okay. That's a slightly better-than-chance guess, not anywhere near a solid basis for speculation.
"Anyways, it makes sense that marathoners get CRC because hunter-gatherers probably don't run that much" is bongcloud lalaland tier guesswork.
By inglor_cz 2026-02-209:33 "makes sense that marathoners get CRC because hunter-gatherers probably don't run that much"
That is a misinterpretation of what I wrote. Let me reformulate.
"Marathons are so much more extreme than what we used to do in the Stone Age, that some pathologies resulting from such long-term physical overload are to be expected." I don't see anything lala about that. You do extreme things, you reap some consequences, sooner or later.
I would say that marathons go beyond our design parameters, but my experience in HN is that the "design" metaphor always conjures some people who consider it a dog-whistle for intelligent design (as opposed to evolution), not just an imprecise metaphor, as metaphors usually are. So I avoid it in order not to attract a senseless fight.
I’m in my early 30s and am starting to think about getting a screening. Problem is, it’s not trivial to do. You have to really upsell your doctor to get one so early, even though it’s a relatively benign procedure.
There is a noninvasive testing method called Shield but it is way too flawed to be reliable (with poor positive rates for malignant tumors)
> even though it’s a relatively benign procedure.
Not completely. Every once in a while they accidentally puncture the intestine with the probes and that becomes a significant medial problem. It doesn't happen often, but that is still a risk that doctors need to consider. If you are over 50 getting one every 10 years is a good idea, and there is some consideration if younger might be worth it. However so few people get colon cancer under 40 that it isn't worth the risks for most - but if there are other signs of a problem (either family history or symptoms) that changes things and it may be worth it.
I was diagnosed at 35 seven years ago with no history. Getting a colonoscopy never crossed my mind, much less being suggested by my general practitioner.
The trigger for me was blood in my stool. It was the slightest amount but I pursued it because that didn’t seem right. Turns out I had hemorrhoids which brought up something I feel hits others - I was embarrassed.
Fortunately the doctor that performed a banding procedure pushed me to get a colonoscopy purely out of being through and seeing the number of incidences increase at my age range.
I often wonder how much the embarrassment factor comes into play here.
By weird-eye-issue 2026-02-202:162 reply Was it a consistent blood in stools or just a one time thing? I've had what I think that is once or twice and then take the approach to just see if it recoccurs a second time before going to a doctor, not sure if that's the correct approach or if a single instance should be alarming enough.
By mitchal 2026-02-2014:06 For me it was small amount consistently. But I cannot stress enough that it was the diagnosis of hemorrhoids coupled with a very proactive doctor that led to me being diagnosed with cancer. It was a lucky circumstance that it was staged early because the additionally suggested screening was not standard protocol for my age.
If you have any abnormalities in your bowel movements (blood, ribboning, etc.) and you have the ability to get it checked then it could offer peace of mind. And yes, there are small chances of intestinal perforations with a colonoscopy.
By drewnick 2026-02-204:11 My bloody stool started slow and took some time off but came back and I had a large polyp. Watch this very closely, but don't panic.
By drewnick 2026-02-204:08 Blood in the stool, at age 41. Benign but a VERY large polyp so I have a followup soon. If you have an instinct to get tested, especially if you have any evidence, do it. My doc fought me to NOT get tested but I persisted. The embarrassment factor is a thing, but we have to get over it!
By bolangi 2026-02-200:26 For a screening procedure recommended as a mass conducted preventative measure in otherwise healthy people, harms must be regulated to a better standard than "doesn't happen often". The study that I read of was about serious issue occuring something like one in 120 procedures. It was done at Kaiser. Next time you're enjoying a sausage, take a moment to look at the sausage skins. If I understand correctly, our intestinal walls are quite thin, and even the colon vulnerable.
If you tell your doctor that a parent had polyps removed (say, recently), that will give you your best chance of getting one. Most likely, if you're in an even remotely progressive area, your doc wants you to have one, but their hands are tied by the insurance company. Afaik you dont have to provide any proof of your claim re parental polyps.
By lotsofpulp 2026-02-1922:163 reply > but their hands are tied by the insurance company.
Doctors' ability to prescribe or refer is never restricted by an insurance company. If they think a patient should get whatever healthcare, they are free to say it.
The average American says US healthcare spending, which is 3x to 20x that of other OECD countries on a per capita basis, is way too high.
The average American also thinks they should be provided testing and procedures that their insurance deems medically unnecessary.
Try to reconcile these two beliefs. (Hint: It's impossible)
By dpc050505 2026-02-2015:12 Maybe there's a bunch of inflated profit margins and people getting filthy rich off a poorly regulated market.
By maxerickson 2026-02-201:402 reply You are just ignoring their intended meaning. Boring.
By lotsofpulp 2026-02-202:24 Is the intended meaning that health insurance should pay for anything and everything? Even systems where the government pays directly like the UK have parameters under which the government will pay for a procedure or medicine.
By nradov 2026-02-206:16 Not at all. Patients are free to pay out of pocket for procedures not covered by insurance. An extra colonoscopy (one not classified as medically necessary), while expensive, is within the financial means of most middle-class adults.
By anoojb 2026-02-1922:28 In CA, my doctor can refer me to get a Cologuard. But it's private pay, and they want payment up front since isurance companies don't restrict doctor's ability, only reimbursement.
So they may not be willing (even though they are able) perform procedure/test if they aren't confident they'll get paid.
By pessimizer 2026-02-1923:211 reply > I’m in my early 30s and am starting to think about getting a screening.
This is a pretty stupid thing to do unless you've had some sort of symptom or family history. Your protection from illness due to screening is statistical, and jumping out of the calculated recommendation just makes it more likely to hurt you (false positives, false negatives, injuries from the procedure) than to benefit you.
Desperately trying to fabricate a reason is just intentionally trying to hurt yourself.
I'm not against colonoscopies (is anyone?) and I personally had my first one early because of an odd pain. Turned out to be unrelated.
edit: the neurotic desperation for disease screening that I see in a lot of people bothers me a lot because it's this odd fetishization of medical science combined with the active subversion of it. For me it's a weird insistence that all tests are good but that the math behind them is not.
From a 'public health' perspective, it makes perfect sense to limit the frequency of screening procedures by age and other broad risk-factors, but that doesn't help at the individual level if you fall on the unlucky side of those statistics.
Most cancers are still very much lethal once they progress to a certain point, and the best treatment we know of is early detection. Many of the cancer screens are harmless or don't add significant risk of death, so it really comes down to money and medical resource availability (also solved with money.)
I don't see much difference in someone paying out-of-pocket for a full-body MRI/colonoscopy vs. them spending way above average on any other item that slightly reduces the risk of dying (how many smoke alarms and fire extinguishers does your home have?)
By dehrmann 2026-02-204:00 > that doesn't help at the individual level if you fall on the unlucky side of those statistics
As GP stated, there's the other unlucky side of the statistics with false positives.
By helterskelter 2026-02-1921:272 reply Lie about family history, but even colonoscopies are not perfect; I just had somebody in my family die of CRC because...
- They had symptoms and wanted a screening, but their PCP repeatedly denied them a referral for like a year because they were "too young".
- They lied about family history after symptoms got worse and got their referral.
- They got the colonoscopy which came back clean, and then symptoms continued to get worse.
- Finally their doctor gave them a referral for an MRI.
Results were stage 4 CRC. The doctor performing the colonoscopy missed the tumor, which was tucked into the sigmoid (the bend in your colon), where he didn't properly inflate because he wasn't taking it very seriously. It had a thumb-tip sized protrusion inside the colon but had gotten huge on the opposite side of the colon wall. They fought it for 8 years after the diagnosis and over 100 rounds of chemo (!!!), were about to get a new procedure at Yale, in which the doctor told them to think of it in terms of "this really may be a complete cure", but it was canceled because of the Big Beautiful Bill.
If you have symptoms (even if you don't), don't let some fuckass Nurse Practitioner tell you no. They don't know shit and they let their egos get in the way when they have to deal with moderately informed patients advocating for themselves. This was preventable and tge medicap system failed them because both the PCP and the doctor performing the colonoscopy were not paying attention to what they were being presented with and saw only their own expectations.
Also...apparently doctors wanted to lower the screening age to like 35, but insurance companies fought it, so it's at 45.
By lotsofpulp 2026-02-1922:23 >Also...apparently doctors wanted to lower the screening age to like 35, but insurance companies fought it, so it's at 45.
On this website, it is frequently opined that because health insurers have a legal minimum medical loss ratio, that health insurers prefer inflated costs so that their medical losses are higher, which means their premiums can be higher, which means their revenue is higher, which means their profit is higher.
I would have thought health insurers would support a lower screening age, especially since it would inflate costs for all insurers so everyone's cut of the now bigger pie gets bigger.
IANAL, just a CRC survivor and one who had my PCP miss my diagnosis a year before I started treatment. You may have a pretty good malpractice claim.
By helterskelter 2026-02-201:48 I'm a little removed from the situation, (not my nuclear family) but I believe the statute is up. It's too difficult to litigate in, say, the first two years of your stage 4 diagnosis before the law won't allow a suit.
I've decided to invest $2000/year and get an MRI scan every year. My first one, the baseline, showed nothing remarkable, thank God. I'm scheduled for my second one in a few weeks, I want to be able to catch anything weird very early on. I think it's worth it despite what all the know-it-alls say.
By thinking_cactus 2026-02-202:03 Can an MRI catch it? It would be ideal if the cost of MRIs came down so everyone could access it. Where's Moore's law for ~tricoders~ MRIs?
By Wowfunhappy 2026-02-202:28 Would an MRI detect polyps?
By jorblumesea 2026-02-1922:361 reply while it sucks, paying for it out of pocket is probably cheaper if you can't get it covered. In the long run, $1500 as a bridge until your 40s feels cheaper than stage 4 cancer.
By rootusrootus 2026-02-201:32 $1500? That sounds optimistic. I'm getting an upper endoscopy tomorrow and they've already told me it will be $4K. The equipment is similar, I expect colonoscopy is not cheaper.
