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If the authors don't draw conclusions from that, I wouldn't either. For example, suppose the main impact of exercise on cancer risk were simply the correlation
by bo1024 2y ago
If the authors don't draw conclusions from that, I wouldn't either.
For example, suppose the main impact of exercise on cancer risk were simply the correlation with time spent outdoors in the sun. Then you would expect to see a chart like this. But a conclusion like 'limit running to 3 hours/week, while walking can be up to 12 hours/week' would be totally wrong.
- Mathnerd314 2y agoThey do draw that conclusion - "the lowest point estimate for all cause mortality was approximately 2000 MET min". What their analysis did not identify is what level of exercise beyond that results in a significant increase in mortality risk. If you look at the individual studies that have categories above 2200, (Slattery 1989, Arraiz 1992, Besson 2008, Kvaavik 2010, Paganini-Hill 2011, Brown 2012, Arem 2015, Huerta 2016, Klenk 2016, Celis-Morales 2017, Lear 2017, Zhou 2017, and Liu 2018), there is some variation - almost every study shows a U-shape, but the lowest point differs by gender, age, measurement method, BMI, and so on. And the effects of too much exercise are small compared to the effects of too little, so it is not surprising that their basic univariate analysis with Stata glst is unable to resolve it. But given the number of U-shape studies I think it is reasonable to conclude that some amount is too much - in the absence of reliable statistics I would say to trust one's body and if it feels like you are pushing yourself hard every week then cut back.