2. Why so confrontational? If you know the answer to the question, why not summarize it? Is the answer to the question so complicated that it would take more time and energy than the two paragraphs you composed in derision?
> If you know the answer to the question, why not summarize it? Is the answer to the question so complicated that it would take more time and energy than the two paragraphs you composed in derision?
Every science article posted on HN gets the exact same treatment where well-intentioned but scientifically ignorant posters fill the comment section with drive-by posts saying "Correlation != Causation" or "Did they correct for [obvious variable]".
It's exhausting and completely unproductive.
If they would take 30 seconds and actually read the source information, they would answer their questions and the comment threads wouldn't devolve into this annoying meta conversation.
Take the post that prompted this whole thing;
> Did they describe how they controlled for behavioral habits? It seems like, as a group, the type of people who would drink large amounts of sugary soda would be less likely to make healthy behavioral choices in other aspects of their life, compared to people who drink fruit juice or diet soda. This could also explain the disparity between soda and non-carbonated sugar-sweetened beverages
> This study doesn't seem to show that soda ages you (as the article states), but instead that sugary soda consumption indicates a tendency towards other activities/habits that may prematurely age you.
So a poster, that later admits he didn't read the article, not only discounts the research that a half dozen PhDs in public health performed, but then provides his own summary of their research that is completely at odds with their results and experience.
How is this helpful?
If one were trying to troll a comment section to waste everyone's time, that's literally the best tactic since anything more obvious would be flagged or ignored.
And completely accurate. You know what's more exhausting than seeing someone point out that correlation!=causation? Being whiplashed by a dozen different studies, or correlation after correlation failing when subjected to a randomized test.
In this case, all you have to do is look at how they tried to defend against the universal healthy user bias (you know, the same thing that led to such epic fails as hormone therapy?), and see that all they did was adjust for weight and some self-reports. Bzzt. On top of that, note the anomalies:
> Only the sugary, bubbly stuff showed this effect. Epel didn’t see any association between telomere length and diet soda intake. “The extremely high dose of sugar that we can put into our body within seconds by drinking sugared beverages is uniquely toxic to metabolism,” she says. She also didn’t see a significant link between non-carbonated sugary beverages, like fruit juice, which Epel says surprised her.
You know what sugar-juice and diet soda have in common? People think they're healthier than regular soda.
They actually adjusted for age, smoking (never, former, current), pack-years of smoking, energy intake using the USDA's HEI, alcohol intake, physical activity (some/none), BMI, and waist circumference. They also didn't include anyone with prexisiting cardiovascular conditions or diabetes.
Their results confirmed earlier studies very strongly -- race, 'never' smokers, younger age, and healthy weight all corresponded to longer telomeres (P < .001), and their results showed significance with sugary sodas.
> You know what sugar-juice and diet soda have in common? People think they're healthier than regular soda.
I'm not sure what you're trying to imply with this one though. Just read page 5 of the actual study. This is good science and generic insults are just noise when everything is actually addressed:
http://www.chc.ucsf.edu/ame_lab/pdfs/Leung%20et%20al%202014a...
All of which are self-reports (food and energy intake as a self-report, when it's well known in the field that self-reports are flattering? and you have the gall to imply that this is good reliable science) or based on weight, just as I said. Please think a little more about this.
> I'm not sure what you're trying to imply with this one though.
What...? OK, I'll charitably assume you're just ignorant here of problems with dietary research and explain (hopefully I won't be wasting my time and receive a response of 'I WANT TO BELIEVE'): whenever a large regression like this is run, there are always many correlations with various behaviors and food consumption; for example, people who eat nuts or blueberries or who exercise regularly or take statins are also people who tend to live longer on average or have other good outcomes. It is tempting to implicitly assume that eating blueberries is a random practice in the population and so this shows that blueberries probably cause you to live longer; however, it is also true that blueberries are widely believed by the general population to be healthy foods, and so the sort of people who pay for and eat blueberries (or claim to eat them, anyway) are also the sort of people who are in good health, are health-conscious, will follow their doctors' orders, comply with drug dosing regimens or regularly test their blood glucose, etc. This bias is universal, and this is why, for example, in the infamous Nurses's Study, hormones seemed so great when they turned out to be murderous in randomized practice: because hormones were believed to be healthy, it was healthy compliant nurses who self-selected into use of hormones and because they were healthy and complaint, had good outcomes anyway.
So, what is a warning sign of healthy user bias? It's when the common trait among harmful/beneficial correlates is whether they are generally believed to be harmful/beneficial even when the supposed causal chemical mechanism is inconsistent. In this case, soda is considered by the general population to be unhealthy, diet soda to be healthier (it's got diet in the name!), and fruit juice the healthiest of all. The former seems to be bad, and the latter two good or at least neutral. And why would soda be so harmful? Well, generally you'd suggest the acidicness or the sugar content; except... either of them should cause either diet soda or fruit juice to be harmful (acidicness or very high sugar content, respectively). But there is an explanation resolving the lack of harm for either: people with better health habits or interest will preferentially consume diet soda or fruit juice and avoid awful soda... and if we correlate consumption with outcomes, we'll find the soda drinkers have the worst outcomes. Voila: healthy user bias.
(You see something similar in studies of maternal smoking or smoking by pregnant women; the effect seems dramatic and harmful to the child, but consider this: given that everyone believes only the worst mothers in the world would smoke while pregnant, what sort of woman would over the past decades smoke while pregnant? Probably not one who plans ahead, is self-disciplined, health-conscious, rich, or intelligent, all of which are heritable, and are difficult if not impossible to completely measure in all their manifestations & remove as confounds. If you wanted a more accurate analysis, taking this possibility into mind, you might do something like find women who smoked while having one child and didn't smoke while having a second child, and compare pairs of children; then you'll find that the harmful effects mostly disappear.)
This cannot be adjusted away simply by a few self-reports because it is a systematic subtle effect on all life outcomes - for example, to name just 2 of the lurking confounds, in other studies one can find longevity boosts to IQ and Conscientiousness for what is suggested to be the same exact reason (more likely to understand or carry out good health practices, respectively), but neither of those was measured by this study.
> This is good science and generic insults are just noise when everything is actually addressed: http://www.chc.ucsf.edu/ame_lab/pdfs/Leung%20et%20al%202014a....
Healthy user biases are never 'actually addressed' by a study of this type, that's the point.
However I would not expect it to then give a clear linear link between specific consumption and telomere length as shown in this study, as the confounding factors are unlikely to be directly linked to exactly how much you consume:
"we found that each daily 8-ounce serving of sugar-sweetened sodas was linearly associated with shorter telomeres, roughly equivalent to 1.9 additional years of aging, independent of sociodemographic characteristics and health-related variables"
No, that's also consistent with healthy user bias: drinking soda and healthy attitudes/habits are not binary variables, they both seem like they would be relatively continuous (you can drink 1 can of soda a day, or 2, or 3, or 4, or 5, or anywhere in between for that matter; and you can be very concerned and conscientious about your life, or concerned, or somewhat concerned, or a little concerned), and so you would expect dose-response relationships. There's no less reason to expect linearity from soda/health than soda/telomeres.
(If it was as easy as all that to refute healthy user bias and other confounds, they wouldn't be such a big deal...)
Based on self-reports, though, yes?
Welcome to the internet!
Your confidence, to the contrary, may be borne of ignorance.
http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fj...
Asking 'did the researchers consider X' without bothering to even look at the paper is just posturing. It's on the same level as saying 'this looks shopped - I can tell by some of the pixels and from having seen quite a few shop jobs in my time.' It may be an attempt to signal hard-headedness and intellectual rigor, but absent any specific target for the criticism, it's worthless.
Ugh. Another blanket statement that in no way reflects the actual paper in question.
From your own source he recommends larger studies, cross-team work clear pre-trial hypotheses, and study-registration.
Guess what?
This n=5,300 study was performed by researchers at UCSF, Stanford, Berkeley, and Michigan, they published their intention to run the study prior to running it with a hypothesis that was partially proved wrong (they expected shortened telomeres with noncarbonated SSBs as well as with sugary soda).
What exactly is your issue with this study? Or do you just reject science in general.
I don't think that's the case at all. It isn't a black and white issue, and I certainly don't feel it has been conclusively shown that if I start drinking drinks that are BOTH fizzy and sugary tomorrow, it will result in my telomeres shortening at an unusually high rate as the article claims. Is that really anti science? I don't think so.
And lay folk do find errors in papers all the time, it varies a lot on the paper and the field how difficult that is though. Some papers, the vast majority of scientists would not be able to spot errors, it really depends on how specialist the required knowledge is and there really are no hard and fast rules there.
So given a study that turned out to be false, in general it isn't possible to argue either way as to whether a layman would spot errors, you would have to argue it on a case by case basis.
The one thing we do know is you definitely cannot spot errors without at least reading the thing and going through the working.
2. Yes, the answer to the question is complicated. As I mentioned, it occupies a full page of the study. I could have summarized this in a few words, but the authors had already done that in the abstract and the poster didn't consider that good enough.