Suadicani P, Hein H O, Gyntelberg F
Epidemiological Research Unit, Copenhagen University Hospital, Denmark.
Int J Epidemiol. 1997 Apr;26(2):321-7. doi: 10.1093/ije/26.2.321.
Misclassification of smokers as non-smokers may bias estimates of the excess morbidity and mortality associated with smoking. The issue has been given little, if any, attention in prospective epidemiological studies. This study examined characteristics of potentially misclassified smokers with respect to mortality, morbidity, and risk factors.
A prospective study (within The Copenhagen Male Study, Denmark) used serum cotinine as an objective marker of use of tobacco. A serum concentration of 100 ng/ml was regarded as a relevant threshold for active smoking. In all, 3270 males aged 53-74 years who reported their previous and current tobacco habits, including the use of chew tobacco and snuff, were included. Incidence of all causes of mortality (ACM) during 9 years and death due to ischaemic heart disease (IHD) during 8 years of follow-up were the main outcome measures.
Overall cumulative incidence rates of ACM and IHD were 19.1% and 4.3%, respectively. Of 1405 men who reported being non-tobacco users, i.e. no current smoking and no use of chewing tobacco or snuff, 1377 had levels < 100 ng/ml, 28 men (2%) had levels equal to or above this threshold value and were considered potentially misclassified smokers. They had significantly higher mortality rates, 35.7% versus 14.7%, P < 0.001, than other self-reported non-tobacco users, and a slightly higher prevalence of tobacco-related cancer, and a highly significant higher prevalence of myocardial infarction, P < 0.001. Compared to non-tobacco users with low cotinine, age-adjusted relative risks (95% CI) were 2.4 (1.3-4.5), P < 0.01, for ACM, and 5.3 (95% CI : 2.1-13.4), P < 0.001, for IHD.
Potentially misclassified smokers deviated strongly from other non-smokers with respect to mortality and morbidity. The importance of this reporting bias when estimating the risk associated with active or passive smoking is discussed.
将吸烟者误分类为非吸烟者可能会使与吸烟相关的额外发病率和死亡率的估计产生偏差。在前瞻性流行病学研究中，这个问题即便有过关注，也很少。本研究调查了潜在误分类吸烟者在死亡率、发病率和风险因素方面的特征。
一项前瞻性研究（在丹麦哥本哈根男性研究中）使用血清可替宁作为烟草使用的客观标志物。血清浓度100纳克/毫升被视为当前吸烟的相关阈值。总共纳入了3270名年龄在53 - 74岁之间、报告了其既往和当前烟草使用习惯（包括嚼烟和鼻烟使用情况）的男性。随访9年期间的全因死亡率（ACM）和随访8年期间的缺血性心脏病（IHD）死亡是主要结局指标。
ACM和IHD的总体累积发病率分别为19.1%和4.3%。在1405名报告为非烟草使用者（即当前不吸烟且不使用嚼烟或鼻烟）的男性中，1377人的水平<100纳克/毫升，28名男性（2%）的水平等于或高于此阈值，被视为潜在误分类吸烟者。他们的死亡率显著更高，分别为35.7%和14.7%，P<0.001，高于其他自我报告的非烟草使用者，烟草相关癌症的患病率略高，心肌梗死的患病率则显著更高，P<0.001。与可替宁水平低的非烟草使用者相比，年龄调整后的相对风险（95%CI）对于ACM为2.4（1.3 - 4.5），P<0.01，对于IHD为5.3（95%CI：2.1 - 13.4），P<0.001。
潜在误分类吸烟者在死亡率和发病率方面与其他非吸烟者有很大差异。讨论了在估计主动或被动吸烟相关风险时这种报告偏差的重要性。
