看到了Campbell的解释

http://www.mcspotlight.org/media/reports/campbell_china2.html

In the China study, the analysis of blood samples shows that plasma cotinine (a nicotine metabolite from tobacco smoking) is inversely associated with diseases of affluence including lung cancer but directly associated with diseases of poverty. At first glance, this finding might appear anomalous, since the smoking of manufactured cigarettes in China has been centered mostly around major metropolitan areas such as Shanghai where diseases of affluence are more common. However, high plasma cotinine levels in the rural areas where diseases of poverty predominate, are strongly associated with the use of homemade cigarettes which contain high levels of nicotine (R. Peto, personal communication). Thus the inverse association between plasma cotinine levels and diseases of affluence may be explained by the high consumption of homemade cigarettes in less affluent areas and the lower consumption of homemade cigarettes in more industrialized and more literate regions of the country.