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SaltZookeepergame691 t1_j7gmmpw wrote

The major ‘caveat’ here is that this is a post hoc analysis of a trial that was done to look at something else, and you have to consider that this was one aspect of many they looked at - hence, they findings are only hypothesis generating, and require confirmation.

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lakeland_nz t1_j7i07wr wrote

Absolutely.

And yes, the subset of women that choose to take Vitamin D are almost certainly not representative of the population. That said, there was a treatment and a placebo group who thought they were taking Vitamin D, so by comparing those two groups we can start to see the effect of Vitamin D.

In this case 65.6 vs 57.9 giving a relative risk between 1.02 and 1.25. 1.02 > 1, so my reading is that the Vitamin D resulted in a statistically significant decrease in relative risk. That's very exciting.

Why does it work? Would this also apply to the general population? There are plenty of good follow-up questions.

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rougewitch t1_j7ii3d1 wrote

Wow! So more vitamin d would widen my pelvis to allow passage of my 10lb son?? I wish i knew that before my surprise csection! (Im obvs joking)

Csections suck

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StressedCephalopod t1_j7irwmb wrote

As a male I cannot judge, however I think I've met just as many women who said that they're glad they had c-sections (my partner included). Always found it interesting that the opinions are so split.

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Lupicia t1_j7iwgje wrote

So. I've had both kinds of C-sections.

Planned cesarian like with my twins can be good, but emergency ones are traumatic, especially after a 'failed' labor. This double whammy is very, very physically draining. It took me months to be able to sit up and years to regain full use of my abs (which you use for everything). Then add on the emotional regret and shame of not being able to go 'natural like women are built to do'. And shame from the attending pediatrician for pushing too long. Like I had a choice.

Yeah no obstructed labor followed by emergency C-section is worse (ETA: in my experience) than my kidney stones, worse than broken major bones IMHO.

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StressedCephalopod t1_j7iwq3b wrote

Thank you for the explanation. Sorry you had to go through that as it sounds horrendous (I've had chronic kidney stones much of my life, so... oof).

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Lupicia t1_j7ixq4k wrote

Same! Sorry you're dealing with kidney stones. They suck. If it's any consolation nothing beats kidney stones except that craziness, not even "regular" labor or C-sections or surgery or IUDs. Kidney stones are crazy.

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rougewitch t1_j7iyxcb wrote

Ive had 2 C-sections and chronic kidney stones- stones are worse bc they are like time bombs that will go off whenever they feel like it. The chronic back pain doesn’t help either.

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porkminer t1_j7j4i2l wrote

I'm going to go out on a limb and agree that prolonged pain and difficult recovery mixed with emotional turmoil are absolutely worse than kidney stones. I have chronic stones, several times per year I get stones that barely pass. I'm lucky if I only get 1 or 2 too large to pass. I still don't believe that my suffering equates to yours. Pain is subjective, however, so comparisons are a good way to start an argument.

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Lupicia t1_j7j7lzq wrote

Yikes friend. Have you talked with a urologist? That's not okay. I've passed four or five and that was more than enough to get me referred. I'm surprised if you haven't been urged to get a more effective treatment for recurring stones or at least an analysis of the stone type so you can help dissolve them. Unless you have already?

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porkminer t1_j7j84mq wrote

Yeah, my diet is exceptional strict between my kidney issues and diabetes. Most of them pass with moderate discomfort. Usually only some painful twinges followed by a persistent ache for a few days. The larger ones get toradol and an antibiotic sometimes. The really big ones get a short hospital visit. Urologist and endocrinologist. I also have a cardiologist though that's preventative, not worth the risk with my other issues and family history.

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Lupicia t1_j7j8r5o wrote

Glad to hear you have great care! Be well friend.

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yeahright17 t1_j7jfml1 wrote

I mean, it's still only 65.6%. Presumably people in your situation would still fall into the ~35%.

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SelarDorr t1_j7ilxie wrote

i dont see that as a major caveat. you can have a primary study with multiple secondary outcomes, in which the results of the secondary outcomes are just as meaningful as a study in which those outcomes are the primary.

the results of this analysis are still of a randomized double blind placebo controlled trial that directly compared the treatment group to the placebo group for the outcome in question. the fact that these results were not the primary focus of the study does not change its significance.

if it were a case where sample selection for the primary outcome somehow added a confounder for some of the secondaries, i see an argument there. but as far as i can tell, this wasn't the case here.

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leplen t1_j7io778 wrote

Eh, the more secondary outcomes you allow the more you run the risk of multiple comparisons. If the p-valur is low enough I'm fine with it, but otherwise you get into green jelly beans cause acne territory.

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SaltZookeepergame691 t1_j7jdudj wrote

If you don’t have any hypothesis before you do the trial to statistically “test” (ie through null hypothesis testing) any significant result (regardless of multiple comparisons control) you generate is - by definition - hypothesis generating.

I don’t mean that the trial itself isn’t robust. It is. But the finding is not enough on its own to say “this is real”.

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SelarDorr t1_j7kbdrz wrote

the hypothesis exists when you decide what your secondaries are.

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SaltZookeepergame691 t1_j7kcgnv wrote

This is a post hoc analysis. This was NOT a named secondary! It explicitly says so in the paper, and it’s why I explicitly said it was a post hoc analysis…

For your info, from the reg record:

>Primary outcome measure

>Neonatal whole body bone area, bone mineral content and bone mineral density assessed by dual energy x-ray absorptiometry (DXA) within 10 days of birth.

>Secondary outcome measures

>1. Neonatal and childhood anthropometry and body composition (weight, length and skinfold thickness measurements), assessed within 48 hours of birth

>2. Women's attitude to pregnancy vitamin D supplementation (qualitative study; assessed in main study only). Methodology and timepoints of assessment not yet defined as of 03/03/2008

>3. Childhood bone mass at 4 years

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Chuggles1 t1_j7k1qk0 wrote

Turns out women that get more D, have babies

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twisted_cistern t1_j7l1kd2 wrote

Known in the research trade as a fishing expedition. Need to be followed up by a well designed study intended to investigate this effect

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SaltZookeepergame691 t1_j7l2zkk wrote

Indeed. It’s nice that they are frank about this in the discussion but worrying that they say nothing about it in the abstract. A good journal wouldn’t publish this without an explicit warning that it was a post hoc analysis. Violation of basic CONSORT guidelines.

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