Nyrén O, Bergström R, Nyström L, Engholm G, Ekbom A, Adami H O, Knutsson A, Stjernberg N
Department of Cancer Epidemiology, University Hospital, Uppsala, Sweden.
J Natl Cancer Inst. 1996 Sep 18;88(18):1302-7. doi: 10.1093/jnci/88.18.1302.
Although cigarette smoking has consistently been shown to be positively related to the risk of adenomatous polyp development (benign neoplastic growth of epithelial tissue in the colon), most studies of cigarette smoking and the risk of colorectal cancer have been negative. However, in two large prospective studies in women and men, a statistically significant association between cigarette smoking and an increased risk of colorectal cancer was found, but only after more than 35 years of smoking.
To shed further light on the alleged relationship between long-term smoking and colorectal cancer risk, we performed a retrospective cohort study among Swedish construction workers, with many long-term smokers, complete long-term follow-up, and a large number of observed cases.
We analyzed the association of smoking with colon cancer and with rectal cancer, using data on a cohort of approximately 135000 male construction workers. High-quality exposure information was collected with the use of a comprehensive questionnaire filled out at the time of enrollment in the cohort, from 1971 through 1975. Complete follow-up was achieved through 1991 and the subjects were observed for an average of 17.6 years, thereby contributing approximately 2375000 person-years of follow-up. We calculated age-adjusted rate ratios (RRs) with the use of Poisson-based multiplicative multivariate models followed by further multivariate modeling that adjusted for other variables.
A total of 713 incident colon cancers and 505 rectal cancers were observed. There was no statistically significant association between current smoking status, number of cigarettes smoked or number of years smoking, and risk of colorectal cancer. The age-adjusted RRs were 0.98 (95% confidence interval [CI] = 0.82-1.17) and 1.16 (95% CI = 0.94-1.44) for colon and rectal cancers, respectively, among current smokers, and 1.07 (95% CI = 0.63-1.82) and 1.08 (95% CI = 0.58-2.03) among smokers of 25 or more cigarettes per day, relative to nonsmokers. Among smokers for more than 30 years at the start of follow-up, the age-adjusted RRs were 1.03 (95% CI = 0.85-1.25) and 1.21 (95% CI = 0.96-1.53) for colon and rectal cancers, respectively, relative to nonsmokers. Heavy smokers of cigars and pipes had a statistically nonsignificant tendency toward excess risk for colon cancer, but there was no clear dose-risk trend.
Our large cohort study did not indicate any excess risk of colon cancer in males who were long-term heavy smokers and provided only weak support for an association with rectal cancer. Our data are thus consistent with the majority of previous reports. The reasons for the discrepancies in comparison with recent U.S. data have yet to be identified.
尽管一直以来都表明吸烟与腺瘤性息肉发生风险（结肠上皮组织的良性肿瘤性生长）呈正相关，但大多数关于吸烟与结直肠癌风险的研究结果均为阴性。然而，在两项针对男性和女性的大型前瞻性研究中，发现吸烟与结直肠癌风险增加之间存在统计学显著关联，但这种关联仅在吸烟超过35年后才出现。
为进一步阐明长期吸烟与结直肠癌风险之间所谓的关系，我们在瑞典建筑工人中进行了一项回顾性队列研究，这些工人中有许多长期吸烟者，随访完整且观察到的病例数量众多。
我们利用约135000名男性建筑工人队列的数据，分析了吸烟与结肠癌和直肠癌的关联。在1971年至1975年队列入组时，通过填写一份综合问卷收集了高质量的暴露信息。到1991年实现了完整随访，受试者平均随访17.6年，从而贡献了约2375000人年的随访时间。我们使用基于泊松的乘法多变量模型计算年龄调整率比（RRs），随后进行进一步的多变量建模以调整其他变量。
共观察到713例新发结肠癌和505例直肠癌。当前吸烟状态、吸烟数量或吸烟年限与结直肠癌风险之间无统计学显著关联。当前吸烟者中，结肠癌和直肠癌的年龄调整RRs分别为0.98（95%置信区间[CI]=0.82 - 1.17）和1.16（95%CI = 0.94 - 1.44），每天吸烟25支或更多的吸烟者相对于不吸烟者，结肠癌和直肠癌的RRs分别为1.07（95%CI = 0.63 - 1.82）和1.08（95%CI = 0.58 - 2.03）。在随访开始时吸烟超过30年的吸烟者中，相对于不吸烟者，结肠癌和直肠癌的年龄调整RRs分别为1.03（95%CI = 0.85 - 1.25）和1.21（95%CI = 0.96 - 1.53）。重度雪茄和烟斗吸烟者患结肠癌风险有统计学上不显著的增加趋势，但无明确的剂量 - 风险趋势。
我们的大型队列研究未表明长期重度吸烟男性患结肠癌有任何额外风险，仅为吸烟与直肠癌的关联提供了微弱支持。因此，我们的数据与大多数先前报告一致。与美国近期数据存在差异的原因尚待确定。
