Federal health expert drop flossing from health guidelines • Hacker News Board

Re: Federal health expert drop flossing from health guidelines

#181

Post by saurik » Thu, Aug 04, 2016, 2:22 AM UTC

vonmoltke wrote: post #156

saurik wrote: post #153

Earlier quoted context omitted.

Or, people who were assigned a professional flosser every single school day were also more likely to brush their teeth better and were reminded constantly about their teeth and even possibly taught stuff about teeth and so maybe even ate less sugary things. I don't have access to the paper: did they at least have the professional flosser supervise the self-flossing to control for this? Otherwise this just seems like…

The reference is a systematic review, not a single study; only one study in the review was run as you indicate. Beyond that, I am not sure what you are getting at. The point of the post I posted and the original article here is that self-flossing as an augmentation to brushing does effectively nothing. What you stated corroborates that. Am I missing something?

My point was that from the information in the article that isn't actually clear; it is like when people say that condoms are X% effective as a contraception technique, and so people assume that means that condoms have an X% failure rate, but what they really mean is that "couples who report using condoms as their primary means of contraception have an X% success rate at avoiding pregnancy". While it is interesting from a clinical perspective as to whether "sending a child home and telling them to floss by themselves" is a working strategy or not, it would be taking into account "children don't really floss" and doesn't tell us if an adult who actually knows they are flossing (such as an adult who actually knows they are using the condom every time) has a particular success rate.

Re: Federal health expert drop flossing from health guidelines

#182

Post by Mathnerd314 » Thu, Aug 04, 2016, 3:09 AM UTC

Mathnerd314 wrote: post #178

fpgaminer wrote: post #171

Earlier quoted context omitted.

I am not a dentist, but based on my understanding (derived from reading commentaries by dentists) the "best" would be floss -> brush. Never mouth wash (except when recommended by your dentist for specific conditions). That's derived from the idea that brushing is not about cleaning the teeth. It's about disrupting bio-films and depositing fluoride on the teeth. That's the reason why dentists recommend not rinsing you…

My understanding is that, although possible, if the cancer risk does exist, it's very small; here's an article placing it at 3-4 cases per 1,000,000: http://aaem.pl/fulltxt.php?ICID=1011054 (They cite a 2012 meta-analysis which showed no statistically significant effect of mouthwash) Here's a recent large-sample statistical study: https://healthcare.utah.edu/huntsmancancerinstitute/research... They find an 1.15 odds…

Here is the author saying flossing is useless, a few years ago: http://www.medicaldaily.com/dental-floss-useless-dentist-say...

Re: Federal health expert drop flossing from health guidelines

#183

Post by mikeash » Thu, Aug 04, 2016, 1:51 PM UTC

deelowe wrote: post #180

mikeash wrote: post #146

Earlier quoted context omitted.

Has anyone done the research on the health benefits of rubbing broken glass in your eyes twice a day? Somehow I doubt it. Would you say that we know nothing about it? Personally, I am quite happy to accept based purely on common sense and intuition that this is unlikely to be healthy. Research is just another tool. It happens to be a really good one, and when research contradicts common sense and intuition, research…

> health benefits of rubbing broken glass in your eyes twice a day? I'm sure there are plenty of medical journals documenting the effects of getting abrasive substances in your eyes.

Broken glass isn't abrasive so much as pointy and sharp.

Also, I doubt any of those documented effects are from properly designed studies, nor do they examine a long-term daily treatment regimen. Are you just assuming that daily treatment would be bad based on what happens after one instance, plus common sense and intuition?

Re: Federal health expert drop flossing from health guidelines

#184

Post by mattkrause » Thu, Aug 04, 2016, 6:13 PM UTC

kristianp wrote: post #179

mattkrause wrote: post #157

Earlier quoted context omitted.

I had the opposite reaction: how on earth has no one looked into this!? But if you dig into it, it's horrifying how little "evidence" goes into treating a lot of common medical conditions. For another trivial example, the stuff in Sudafed PE (phenylephrine) http://www.sciencedirect.com/science/article/pii/S1081120610... is much worse than the psuedophedrine it replaced. I wish the NIH (and other funding agencies) wou…

What are the phases in this study? There's no explanation of the phases in the abstract: "Phase 1 results showed a difference between phenylephrine and placebo that was 64% of the difference between pseudoephedrine and placebo, substantially greater than the 17% difference observed for all phases. " Edit: Phase 1 may mean "Testing of drug on healthy volunteers for dose-ranging", from wikipedia: https://en.wikipedia.o…

It means something different here.

That study uses a crossover design, which means that everyone gets all three treatments (in this case, phenylephrine, pseudoephedrine, and placebo), but in different phases. You might get the placebo this week and the pseudoephedrine next week, while I get the opposite. Each one of these time steps is a "phase".

A similar study might use a "batch design" instead, where the subjects are each tested once, after being given a single treatment. They might put you in the pseudoephedrine group, while I get the placebo.

Crossover designs have a big advantage in that are more robust to individual variability, and thus have more statistical power to detect differences. In essence, the crossover design allows you to compare the average of each subjects' difference between conditions while the block designs force you to examine the difference between the average scores of each group.

This power comes at a price--you have to be careful that the different treatments do not interact so you can correctly associate causes and effects. None of the treatments remain in the subjects' system for a week, but they are worried that people might remember* how well pseudoephedrine worked and "downgrade" the other treatments. One way to check this is to analyze the first phase of your data, where each subject has had only one treatment, as a batch design, which is what they reported there.

* The measurement here is a self-reported scale of nasal congestion. Note that they don't do this for most of the quantitative/physiological measurements.