The scientific community is very broad, and there are many groups within that community whose members intermittently produce studies that are either poorly designed, poorly conducted, or poorly presented and explained. Or all three, for all of the usual reasons. Constraints of time and funding, institutional pressure to publish, the involvement of external interests, and so forth. Bad papers do get published, provided that the authors are subtle enough. This does tend to be a self-correcting problem, when considered over a sufficiently long span of time to allow errant individuals and institutions to blacken their reputations with the community at large. Still, at any given moment, one should expect to see that some small fraction of published scientific papers are problematic, rather than merely incorrect.
The problematic paper for today's discussion was published last year, reporting on a study of the effects of hyperbaric oxygen treatment on areas of metabolism that are connected to the study of aging. At the time, claims of reversal of aging were circulating in the media. The paper itself was of poor quality, but far less offensive than the related and entirely unfounded hype. It was the usual circus of ignorant commentary, yes, but also a matter of hyperbaric oxygen treatment providers pushing claims that were completely unsupported by the evidence. Serious researchers will think twice about working with anyone who was involved in this exercise. I talked about this a little at the time, focusing as much on the ridiculous claims being made by institutions involved in the work, and by the media at large, as on issues with the study and interpretation of data. Relatedly, I see that the SENS Research Foundation team have chosen to pick apart the scientific details in a recent article. A little more shaming can't hurt in this case!
Lower-quality, clickbait-hungry media outlets love sensationalist claims, but one does expect better from the public relations department of an internationally-respected research university. And it was an easy jump from the already-overstated "In First, Aging Stopped in Humans" and "treatments can reverse two processes associated with aging and its illnesses" to saying that a treatment "can reverse aging process" - and to then land in a mud-pit of self-parody with "Human ageing reversed in 'Holy Grail' study, scientists say."
The actual findings of a recent study on hyperbaric oxygen treatment (HBOT) were much more limited. Despite some intriguing indicators, the actual impact of HBOT on aging based on this study is entirely unclear, quite plausibly negligible, and in any case objectively less impressive than that of (say) regular exercise, which certainly does not "reverse aging."
The actual details of the study show that even the narrow claims of the study abstract aren't fully justified. It's not clear that blood-cell telomeres were lengthened any more than they would have been without HBOT; it's not clear that "senescent" T-cells were reduced in numbers, let alone actually destroyed; and if "senescent" T-cells had been destroyed, it would not demonstrate a senolytic effect of HBOT. Despite the fact that it's standard terminology in the immunology world, "senescent" T-cells aren't actually "senescent cells" in the sense usually used in the geroscience world. Jumping from post-HBOT reductions in the number of these "senescent" T-cells to potential effects on classical senescent cells is really just a misunderstanding of what kinds of cells are involved in each case.
Even if the study had robustly demonstrated that every one of the points above really did occur, it would not constitute "reversing aging" - or even justify the more restrained claims that "blood cells actually grow younger as the treatments progress" or "that the aging process can in fact be reversed at the basic cellular-molecular level."