West of Scotland Cancer Surveillance Unit, Division of Community Based Sciences, University of Glasgow, 1 Lilybank Gardens, Glasgow G12 8RZ, UK.
J Epidemiol Community Health. 2011 Nov;65(11):1053-8. doi: 10.1136/jech.2010.127555. Epub 2011 Mar 9.
Modifiable behavioural risk factors--including exercise, obesity and smoking--have been causally associated with colorectal cancer mortality. However, results have been inconsistent and undiagnosed cancers may affect baseline risk factors, distorting the temporal relationship that is observed between them.
To determine whether risk factors for colorectal cancers available in the Whitehall I study were predictive of colonic or rectal cancer mortality.
Prospective cohort study over 40 years on Whitehall I men aged 40-69 on entry between 1967 and 1970. Associations between baseline risk factors and cause-specific mortality were tested with Cox proportional hazards models. Events within the first 10 years of follow-up were excluded to minimise 'reverse causality.'
329 colon and 121 rectal cancer deaths occurred among 17,949 men followed up for a total of 472,523 person-years. Age and smoking were associated with increased mortality from colorectal cancers. Compared with never-smokers, current smoking was associated with age-adjusted HRs for colon and rectal cancers of 1.45 (95% CI 1.03 to 2.03) and 1.97 (95% CI 1.02 to 3.80), respectively. A significant effect of current smoking on rectal cancer mortality was only apparent after events in the first 10 years of follow-up were excluded. No convincing evidence was found that body mass index, diabetes mellitus, blood pressure or physical activity were associated with colorectal cancer mortality.
Smoking significantly increases mortality from colorectal cancer and its decreasing prevalence in the UK may partly explain falling mortality from the disease. Changes in health behaviours in response to early cancer symptoms may result in differential misclassification or 'reverse causality' unless early events are excluded. Although many individual cohort studies have not shown significant relationships between behavioural risk factors and colorectal cancer mortality, their contribution to meta-analyses remains important.
可改变的行为风险因素，包括运动、肥胖和吸烟，已被因果关联于结直肠癌死亡率。然而，结果并不一致，并且未诊断的癌症可能会影响基线风险因素，从而扭曲观察到的它们之间的时间关系。
确定 Whitehall I 研究中可获得的结直肠癌风险因素是否可预测结肠癌或直肠癌的死亡率。
这是一项针对 Whitehall I 男性的前瞻性队列研究，参与者在 1967 年至 1970 年间进入研究时年龄为 40-69 岁，随访时间超过 40 年。使用 Cox 比例风险模型检验基线风险因素与特定原因死亡率之间的关联。排除前 10 年随访期间的事件，以最大程度地减少“反向因果关系”。
在随访了 472523 人年的 17949 名男性中，发生了 329 例结肠癌和 121 例直肠癌死亡。年龄和吸烟与结直肠癌死亡率的增加有关。与从不吸烟者相比，当前吸烟者的结肠癌和直肠癌年龄调整的 HR 分别为 1.45（95%CI 1.03 至 2.03）和 1.97（95%CI 1.02 至 3.80）。仅在排除前 10 年随访期间的事件后，才能观察到当前吸烟对直肠癌死亡率的显著影响。没有令人信服的证据表明体重指数、糖尿病、血压或体力活动与结直肠癌死亡率相关。
吸烟显著增加了结直肠癌的死亡率，而英国吸烟率的下降可能部分解释了结直肠癌死亡率的下降。由于早期癌症症状的变化，健康行为的变化可能导致不同的错误分类或“反向因果关系”，除非排除早期事件。尽管许多单独的队列研究未显示行为风险因素与结直肠癌死亡率之间存在显著关系，但它们对荟萃分析的贡献仍然很重要。
