Serum cotinine levels in pipe smokers: evidence against nicotine as cause of coronary heart disease.Lancet. 1981 Oct 10; 2(8250):775-7.Lct
Serum levels of cotinine (a principal metabolite of nicotine) were studied in men who did not smoke (28), and in men who smoked cigarettes only (150), cigars only (70), and pipes only (56). The mean cotinine level for pipe smokers was 389 ng/ml, significantly higher than the mean level for cigarette and cigar smokers (306 and 121 ng/ml, respectively); no cotinine was detected in the serum from any of the non-smokers. Large prospective studies have shown that pipe smokers have no material excess risk of coronary heart disease but cigarette smokers do, so that our observations indicate that nicotine is unlikely to be the major cause of the excess coronary heart disease mortality in cigarette smokers.