This article and title seem fairly clunky because they are using a single aspect of obesity to make larger inferences. I don't necessarily disagree with their conclusion, just that the way it is written in this article doesn't lay it out very straight forwardly. Here are the basic findings in the article.

They took the medical understanding that obesity is often accompanied by inflammation (they focused on a specific form of inflammation) and they did some tests on mice showing that gaining a lot of weight may possibly trigger epigenetic changes which result in the inflammation persisting even after the weight was lost.

The conclusion is that losing weight (for overweight mice, and possibly then people) comes with a host of health benefits but that some of the bodily changes caused by being overweight (specifically inflammation) may be longer lasting and may not disappear just by losing the weight again. In those cases, they believe we may need to consider the longer term effects of being overweight even AFTER the weight is lost and not simply stop examining the effects of obesity once the weight is lost.

Even more simply: Obesity causes health problems. Some of those problems may linger even after the mouse (or person presumably) is no longer obese. Some obesity caused bodily stress may persist even after weight is lost and should continue to be taken into consideration.

I'm sure the large size of linemen is contributing to the worse outcomes they seem to experience in relation to the other positions. Larger people still have the same size joints and bones. Their cardiovascular system would have to grow to supply a larger body with enough oxygen. All of that can contribute to arthritis, high blood pressure, etc.

It seems like the study is mostly finding a generic link between playing a contact sport at a very high level and some advanced aging outcomes over time. They further find that linemen as a group are experiencing a larger proportion of those advanced aging outcomes relative to other positions.

They say that there could be many factors involved and that further study to isolate those factors is needed. This study simply makes a link between professional football and advanced aging on some areas related to health.

Head injuries is not a bad supposition at all but that's why the science is being done.

Is dementia more common amongst ALL player or just certain positions?

Does being a larger person in general contribute to rates of dementia?

Are there other genetic factors that make someone more likely to be successful as a professional football player that also contribute to likelihood of dementia?

Are all head injuries more likely to lead to dementia or are there certain types that do? Are a handful of bigger hits to the head over a career more or less damaging than a lot of smaller head hits sustained consistently over a career?

Understanding all of the possible mechanisms can help inform players and possibly help tweak rules to mitigate the known risk factors through rule changes.

Yeah. That's a striking difference that is unlikely to be purely reporting or selection bias. It would be interesting to further differentiate by position to try and narrow down the possible variables. Like, do punters see similar numbers? Do corners? There is so much speciation in football by position when it comes to body size and play style that it could yield some results that may help the game adjust to mitigate some things.

I think this interesting and is very much worth studying but playing football professionaly is labor intensive. I wonder what the findings would be if we isolate other labor intensive jobs as well like roofers or brick layers. Would we also find more high blood pressure, arthritis, and dementia?

Secondarily, we could look at the selection bias of professional football players. I would bet we would find that people who reach puberty at younger ages, have higher levels of certain hormones, are naturally taller/larger, and have more "early aging" traits in general may be favored in youth sports because of their earlier development and therefore more likely to play college and pro.

It could be a combo of the physical toll of the sport professionaly AND genetic selection bias of those more likely to play the sport.

Edit: Just finished reading the study and it's genuinely interesting. Hopefully studies like this can be used to find ways to mitigate prevalence of heath issues in the sport. In the end though, I feel that anyone competing in sport at the highest levels will likely find that pushing themselves physically that much is not the easiest path for their bodies. It's a trade-off.

They do acknowledge the possible impact of selection bias within the survey itself. "Third, we acknowledge the possibility of selection bias within the ASF cohort and cannot exclude the possibility that ASF players harbouring more illness may have been more likely to enroll."

Secondly, they acknowledge the impact of position within the sport showing that linemen have much higher reported issues than other positions.

They also acknowledge that it is a self reported survey which may introduce some skewing and that "race" and systemic racism may have a skewing effect. As well, they acknowledge the possible impact of related activities such as strength training, anti inflammatory drugs, and other possible drugs/ related activities.

They also acknowledge that other professional sports including hockey, soccer, and rugby also show increased rates of the selected conditions (but don't mention to what relative degree).