I tend to ascribe some value to "It was published in the peer-reviewed British Medical Journal."
Additional thought: Especially because it is essentially supporting the null hypothesis.
Well, one can't criticize the quality of the study without looking how well other studies did. But even if all studies involve a massive drop-out rate, the drop-out rate still seems like something to look at in evaluating the accuracy of the study.
I mean my concern, looking from the outside, isn't relative accuracy, but absolute accuracy. Not "is it as good as other studies?" but "it is good enough that I can rely on it?"
BTW, it would also be an issue if the subjects were compensated to the point that they differed from the actual population at large.
Fundamentally having more respect for doing things right, the right way, over the /long/ term, including the STEM fields, would be a 'good thing' for any society, but particularly western ones (where often the bad/evil antagonist is based on science or a cold lack of emotions; but the protagonist is based mostly on emotion and feeling instead of logic).
Everyone keeps replying as if my comments imply a demand that "something be done about this". That's not my point. Maybe nothing can be done about it. The situation is still significant or at least appears significant.
It's called longitudinal analysis or survival analysis, depending on the question being asked.
We statistician got test and models for these.
You can rely on it if the people who are conducting the experiment are competent and know what they're doing.
You absolutely can.
Scientific studies should be judged on their potential to produce interesting results. This study has too small a sample size to provide results that merit making even the weakest claims about. Even the initial sample size was, frankly, just barely large enough to maybe provide suggestions for future research.
If a meaningful drop-out rate is expected, I would argue that the researchers running these sorts of studies are mostly wasting everyone's time and money for the sake of publishing a few papers.