If you run these curves only on non-smokers you get rid of that J at the end of the curve and you get pretty much a function that's to the right of the curve here.

如果仅在不吸烟人群中做统计,那么左末端就不会出现J形曲线,而是会得到一条,从左到右逐渐上升的完美的函数曲线

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