This is a beautiful conjecture!

The problem is amusingly circular. Even if you reject the conjure in parent comment, you will be tempted to reduce the number of birthday surgeries due to the increased mortality. This will mean that birthday surgeries are only done in even more desperate circumstances which of course will increase the risk.

So mitigation of this problem will lead to the percentage increasing even more! Actually, it turns out that it is possibly better if the percentage is high!

You could control for patient characteristics (age, severity of the condition, etc), and that was indeed done here, see the paper. It also specifically addresses this issue:

> The major threat to the internal validity of our findings is that surgeons may selectively operate on sicker and more complex patients on their birthday, perhaps because those patients cannot have their procedures delayed. However, this is unlikely to explain our findings because we found that patients who underwent surgery on the surgeon’s birthday were similar in all observable characteristics to patients who underwent surgery on other days. Furthermore, severity of illness as measured by predicted mortality, and the number of procedures performed per surgeon, also did not differ based on whether a surgery occurred on a surgeon’s birthday compared with other days.

It seems to me that the analysis is quite carefully done:

> Findings were qualitatively unaffected by: using in-hospital mortality instead of 30 day mortality; additionally adjusting for the timing of the surgery; including both hospital and surgeon fixed effects in the same regression models; excluding potentially outlier surgeons with the highest mortality; using logistic regression models instead of linear probability models: using random effects models instead of fixed effects models; restricting our analysis to surgeons who performed procedures on their birthdays; additionally adjusting for the day of the year; or excluding surgeons who were born on the outlier birthdays (supplementary eTables 5-13). [...] The study findings were qualitatively unaffected when the analysis was restricted to procedures with the highest average mortality or to patients with the highest severity of illness (supplementary eTables 16 and 17).

This is a great point to raise, but it's worth noting that it directly contradicts the GP's anecdotal observation. Had they instead found greater severity on birthdays and attempted to statistically correct for it, the two would be compatible. Instead, they looked, and found that there was no underlying difference to correct for. The question then becomes whether the GP is wrong, whether the hospital in question didn't have such a policy, or whether the measurements used in the study were insufficient to pick up the difference in severity.

I don't know which of these is true, but despite the apparent statistical significance of the finding, I wouldn't be confident assuming that the result is generally applicable. While not impossible, it strikes me as suspicious that they found no differences whatsoever in the surgeons' birthday vs non-birthday schedules. I somewhat wonder if by "no difference" they really meant "no statistically significant difference", which in this case wouldn't justify their lack of adjustment.

Furthermore, note that there really is a significant "avoiding surgeries on birthdays" effect: 2064 in 980,876 operations were done on a birthday, which is 1 in 475, rather than the 1 in 365 if there were no such effect. That's a reduction of 23%, which is rather suspicious given that we're trying to explain a 23% increase in mortality rate.

So what mechanism is responsible for that reduction, and is it likely to affect surgeries differently based on how urgent and specialized (and therefore dangerous) they are? Since the authors restricted it to surgeons that have done at least one surgery on their birthday, that rules out blanket "never on birthday" policies. It seems like the only mechanism that wouldn't affect them differently is "the surgeon is already on vacation in another country and can't get here for the operation" (and they choose to take vacations on their birthday more frequently). One could probably check vacation-day records relatively easily...

I think you have it backwards. The risk of the individual surgeries is not increased. Only the risk that a surgeon will be confronted with an above average critical surgery is increased.

It is not even clear that there actually is a problem. It's just a weird way to slice the data to produce an effect.

> The risk of the individual surgeries is not increased.

They never said that it did (unless they've edited their comment since you replied to it). They just said that the percentage [of deaths on surgeons' birthdays] will increase, and that is correct.

I do not completely understand your points.

Shouldn't hospitals have multiple surgeons?

If one of them is on vacation, the other one does the work, and vice versa?

But the more you avoid birthday surgeries altogether, the more those that end up still happening are extreme cases with high mortality rates. So if your target is to avoid this scary statistical anomaly, you might instead want to promote more benign surgeries on birthdays.

The types of surgeries performed should be controlled for when performing a statistical study.

They were. This entire line of criticism comes from not reading the study methods.

I don't think surgeons are fongible assets. There is a lot of planning and study taking place before a complex operation. Not to mention most surgeons have specialties.

The long term plans and studied for surgeries can be moved one day forward or backward basically by definition.

Except if something changes suddenly and surgery is suddenly needed - that’s what makes it an emergency.

A surgeon seems more fungible than a developer, to me.

All sorts of standards, compliance, and licensing requirements.

Surgeons are generally specialists in one particular area and possibly even specialists within that area (ie: only do knee replacements, etc.). Surgeons get better with experience, it's a skill, and different surgeries are different enough that experience doesn't transfer too much. There's also changes over time in best practices so skills degrade not just due to lack of recent experience. If I remember the best predictor of the outcome of your surgery is how many similar surgeries the doctor does per year.

Nobody's making any points about developers

My gut instinct is that this is incorrect, too, but I don't know enough about surgery to make a compelling argument.

I'd back myself to pick up Ruby (a language I've never touched before) and be productive, more than I'd trust a surgeon who only has experience with heart surgery to operate on my brain. Maybe that's ignorant of me.

Even if a Ruby bug would mean death?

EDIT: I take this back. I missed the point of the argument.

That'd change the risks, sure.

I don't think that's the scenario @jrh206 was talking about, though. Most code written in Ruby doesn't have the sort of immediate risk to life or limb surgeries do.

Those requirements are fairly general.

They don't test for "I've been doing this particularly tricky type of bone biopsy right next to the spinal cord for decades" scenarios.

For non-emergency surgeries it's often a long-term relationship where the same doctor who has seen the patient a few times would be the one operating - so if that particular surgeon isn't available for whatever reason, the planned operation would be rescheduled to a different date with the same doctor, not to a different doctor in the same day.

There’s research, consultations, who is covered under what insurance, etc.

Yes, it does really mean you need to dig into actual causation or the law of unintended consequences will bite you in the ass.

> If this is fairly standard practice, then an afternoon birthday surgery would be an emergency situation and, hence, more deadly

This is spot on. The causality can be both ways.

Note that it would be interesting to dig into what is really computed here, because the whole wording seem intentionally sensationalistic.

1) "23% more likely to die" seems _huge_, but it applies to an already very small chance. The mortality rate just goes from 5.6% to 7%. Using this logic, moving from 0.1% mortality rate to 0.3% would mean "you are 3 times more likely to die".

2) Comparing mortality rates only make sense if the distribution of operation complexity are identical for these days. As the parent post suggest, it seems very likely that low complexity operations are postponed after a surgeons birthday.

3) Where are the confidence intervals? I refuse to even consider looking at a statistics if error boundaries and significance metrics are not provided.

That may very well all be provided in the underlying paper, but the article itself does not really discuss these points.

> 1) "23% more likely to die" seems _huge_, but it applies to an already very small chance. The mortality rate just goes from 5.6% to 7%. Using this logic, moving from 0.1% mortality rate to 0.3% would mean "you are 3 times more likely to die".

But that is indeed precisely what it means. The 737 MAX might have increased the accident rate from 1 in a million to 3 in a million, and that would have been a tripling. That is not sensationalistic.

> 3) Where are the confidence intervals?

In the paper: "(7.2% v 5.6%; adjusted difference 1.6%, 95% confidence interval 0.4% to 2.8%; P=0.01)"

As soon as I saw the article title, I said "That 23% doesn't mean anything by itself - I need to see the numbers".

Aren't we doing here statistics on a one-surgeon sample size?

Where is the "one surgeon" sample size?

It's about the success of surgery on that surgeon's birthday, and calculating the implications of switching the surgery types etc etc, while in a real world situation you'd just use the other surgeon - which hopefully has another birthday. I agree there's gonna be some smaller effect even then, but less and less the more surgeons you have and the more randomly distributed their birthdays are.

> If this is fairly standard practice, then an afternoon birthday surgery would be an emergency situation and, hence, more deadly.

As pointed out by jlebar, this is controlled for by comparing similar emergency surgeries.

"The patients were all Medicare beneficiaries aged 65 to 99. They had all undergone one of 17 common emergency surgical procedures between 2011 and 2014."

There are emergencies, and there are EMERGENCIES. The former can often wait 24 hours; the latter cannot wait at all. Medicare data does not capture that at all - it only captures the categorical, "surgery type."

e.g., someone has a run of the mill cholecystitis that needs to come out. It can go when there's an opening in the surgical schedule, or tomorrow morning. That's an "emergency" - it came in through the ED, wasn't elective.

Then there's the person w/ chole that looks septic and you're afraid they're going to perf or already have. That person is going to the OR now.

Under Medicare coding, both of those are lap choles, CPT 47562. This doesn't control for that at all, except in the broadest of ways.

Also, a 65yo surgical candidate and a 99yo surgical candidate are wildly different. 99yo isn't going under the knife for anything other than immediate threat of death or unendurable pain. In the lap chole example above, I'm going with a trial of abx in the 99yo unless he's absolutely about to perf; 65yo, sure, let's take the gallbladder out - once he's progressed to sx chole, odds are really good it'll have to come out within the next two years. I think most surgeons would rather do it at 65 than 67.

Looking at the 2x2 of 65, 99, emergency, and EMERGENCY, you capture an incredibly large variety of severity and risk.

> If this is fairly standard practice, then an afternoon birthday surgery would be an emergency situation and, hence, more deadly.

TFA says they're only counting emergency surgeries, to avoid exactly this bias.

This is the most frustrating pattern in online discussion of science. A post title presents a conclusion, then the top comment proposes some alternative cause of the conclusion or some hypothesized methodological weakness in the research, then readers assume that the research is bad. Often, the exact specific criticism appears directly in the paper because the researchers thought of that too.

> Often, the exact specific criticism appears directly in the paper because the researchers thought of that too.

From the paper:

"The major threat to the internal validity of our findings is that surgeons may selectively operate on sicker and more complex patients on their birthday, perhaps because those patients cannot have their procedures delayed. However, this is unlikely to explain our findings because we found that patients who underwent surgery on the surgeon’s birthday were similar in all observable characteristics to patients who underwent surgery on other days. Furthermore, severity of illness as measured by predicted mortality, and the number of procedures performed per surgeon, also did not differ based on whether a surgery occurred on a surgeon’s birthday compared with other days."

No reason to be frustrated. Things are almost never right or wrong, particularly in complex science.

In this case, based on another comment above about "emergency procedure" having multitude of meanings, you're most likely wrong in that the paper has a rebuttal to the top post. The hypothesis then, is that the actual urgency of surgeries is not controlled precisely enough to state that they cannot affect the measurement.

From the sibling comment.

> The major threat to the internal validity of our findings is that surgeons may selectively operate on sicker and more complex patients on their birthday, perhaps because those patients cannot have their procedures delayed. However, this is unlikely to explain our findings because we found that patients who underwent surgery on the surgeon’s birthday were similar in all observable characteristics to patients who underwent surgery on other days. Furthermore, severity of illness as measured by predicted mortality, and the number of procedures performed per surgeon, also did not differ based on whether a surgery occurred on a surgeon’s birthday compared with other days.

> we found that patients who underwent surgery on the surgeon’s birthday were __similar in all observable characteristics__ to patients who underwent surgery on other days

Not exactly the same by similar:

My father is a surgeon at a small hospital and my mother just got her hip replaced a few weeks ago (at a different, larger city hospital) and the first thing he insisted on was she was scheduled as the first patient of the day.

My father is a physician. He always recommends that if you are getting a test done, try to schedule it for the middle of the week and not near a holiday. It seems the lab techs make more mistakes on Fridays, weekends, etc. Just his anecdotal experience.

Simpson's paradox: https://en.m.wikipedia.org/wiki/Simpson%27s_paradox

I think it'd be more accurate to describe this as suvival bias, where the worse cases "survive" (i.e. they get to be done on that day).