This article is likely to become the basis of "indisputable evidence" and various government policies. Yet the study is seriously flawed: none of the cohort studies included in this meta-analysis studies people who smoke one cigarette a day, and the risk of this pastime is mathematically extrapolated, both in every included study and meta-analysis. This flaw is obvious to anybody who bothers to read more than a summary and has been noted by many professional epidemiologists. The page of rapid responses has been fun to read:Conclusions Smoking only about one cigarette per day carries a risk of developing coronary heart disease and stroke much greater than expected: around half that for people who smoke 20 per day. No safe level of smoking exists for cardiovascular disease. Smokers should aim to quit instead of cutting down to significantly reduce their risk of these two common major disorders.
https://www.bmj.com/content/360/bmj.j58 ... -responses
I am not even going to the association-causation argument. I don't smoke, except an occasional cigar once or twice a month and do not advocate it. Yet junk science just doesn't do any good. Every time I read an article of such sort the first thing that comes to mind is the reference to the "indisputable evidence" that climate change is caused by human activity. Specifically the Hockey Stick by Mann. They also used flawed input and also refused to make their database available to other researchers for a long time.