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Objective The association between smoking and breast cancer has been found in most recent, large cohort studies. We wanted to investigate how smoking-associated breast cancer varies by level of education, a well-established measure of socioeconomic status. Methods We included 302,865 women with 7490 breast cancer cases. Participants were assigned to low, moderate or high level of education and analyzed by smoking status (ever/never), and stratified by birth cohorts (⩽ 1950 >). We used Cox proportional hazard to estimate hazard ratios (HRs) and confidence intervals (CIs), adjusting for age, number of children, age at first childbirth, BMI, age at enrollment and physical activity. Results Women born ⩽ 1950 with low and moderate levels of education had a 40% increase in smoking-associated breast cancer risk (HR = 1.40, 95% CI 1.25-1.57 and HR = 1.14, 95% CI 1.05-1.24, respectively). Women in the same age group with high level of education did not have an increase in risk. No increased breast cancer risk was found among women born after 1950 for any level of education, when analyzed by smoking status. Longer duration of smoking before first childbirth was consistently associated with increasing risk of breast cancer in all three categories of education (all p for trends < 0.01). Conclusion Smoking for several years before first childbirth increases the risk of breast cancer, regardless of educational level. [ABSTRACT FROM AUTHOR]

Several recent cohort studies have found an association between smoking and breast cancer, but the association between lifetime smoking exposure and breast cancer mortality is less well described. We examined whether smoking before breast cancer diagnosis is a predictor of breast cancer mortality in a large cohort with more than 4.1 million years of follow-up, with a special focus on women who initiated smoking before first childbirth. Information on smoking status was collected before breast cancer diagnosis and used to estimate hazard ratios ( HRs) and corresponding 95% confidence intervals ( CIs) of breast cancer mortality in a cohort of 302,865 Norwegian women with 1106 breast cancer deaths. Women were enrolled between 1974 and 2003 and followed up through linkages to national registries until 31 December 2007. We found that breast cancer mortality was slightly but significantly increased for current (HR = 1.15, 95% CI 1.01-1.32) and ever (HR = 1.15, 95% CI 1.02-1.30) smokers as compared to never smokers. No statistically significantly increased mortality was found for women who initiated smoking before first childbirth, and no dose-response association was revealed for any of the different measures of smoking exposure. A large proportion of heavy smokers may have died from other causes than breast cancer during follow-up, possibly diluting our results. This study found that lifetime smoking exposure had a significantly increased risk of breast cancer mortality compared with never smokers. [ABSTRACT FROM AUTHOR]

Background: Smoking has recently been established as a risk factor for rectal cancer. We examined whether the smoking-related increase in rectal cancer differed by gender. Methods: We followed 602,242 participants (49% men), aged 19 to 67 years at enrollment from four Norwegian health surveys carried out between 1972 and 2003, by linkage to Norwegian national registries through December 2007. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by fitting Cox proportional hazard models and adjusting for relevant confounders. Heterogeneity by gender in the effect of smoking and risk of rectal cancer was tested with Wald χ². Results: During a mean follow-up of 14 years, 1,336 men and 840 women developed invasive rectal cancer. Ever smokers had a significantly increased risk of rectal cancer of more than 25% for both men (HR = 1.27, 95% CI = 1.11-1.45) and women (HR = 1.28, 95% CI = 1.11-1.48) compared with gender-specific never smokers. Men smoking =20 pack-years had a significantly increased risk of rectal cancer of 35% (HR = 1.35, 95% CI = 1.14-1.58), whereas for women, it was 47% (HR = 1.47, 95% CI = 1.13-1.91) compared with gender-specific never smokers. For both men and women, we observed significant dose-response associations between the risk of rectal cancer for four variables [Age at smoking initiation in years (both ptrend <0.05), number of cigarettes smoked per day (both ptrend <0.0001), smoking duration in years (ptrend <0.05, <0.0001) and number of pack-years smoked (both ptrend <0.0001)]. The test for heterogeneity by gender was not significant between smoking status and the risk of rectal cancer (Wald χ², p -value; current smokers = 0.85; former smokers = 0.87; ever smokers = 1.00). Conclusions: Smoking increases the risk of rectal cancer to the same extent in women as in men. [ABSTRACT FROM AUTHOR]

Background Smoking has recently been established as a risk factor for rectal cancer. We examined whether the smoking-related increase in rectal cancer differed by gender. Methods We followed 602,242 participants (49% men), aged 19 to 67 years at enrollment from four Norwegian health surveys carried out between 1972 and 2003, by linkage to Norwegian national registries through December 2007. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by fitting Cox proportional hazard models and adjusting for relevant confounders. Heterogeneity by gender in the effect of smoking and risk of rectal cancer was tested with Wald χ². Results During a mean follow-up of 14 years, 1,336 men and 840 women developed invasive rectal cancer. Ever smokers had a significantly increased risk of rectal cancer of more than 25% for both men (HR = 1.27, 95% CI = 1.11-1.45) and women (HR = 1.28, 95% CI = 1.11-1.48) compared with gender-specific never smokers. Men smoking ≥20 pack-years had a significantly increased risk of rectal cancer of 35% (HR = 1.35, 95% CI = 1.14-1.58), whereas for women, it was 47% (HR = 1.47, 95% CI = 1.13-1.91) compared with gender-specific never smokers. For both men and women, we observed significant dose--response associations between the risk of rectal cancer for four variables [Age at smoking initiation in years (both ptrend <0.05), number of cigarettes smoked daily (both ptrend <0.0001), smoking duration in years (ptrend <0.05, <0.0001) and number of pack-years smoked (both ptrend <0.0001)]. The test for heterogeneity by gender was not significant between smoking status and the risk of rectal cancer (Wald χ², p -value; current smokers = 0.85; former smokers = 0.87; ever smokers = 1.00). Conclusions Smoking increases the risk of rectal cancer to the same extent in women as in men. [ABSTRACT FROM AUTHOR]

Background: Smoking has recently been established as a risk factor for rectal cancer. We examined whether the smoking-related increase in rectal cancer differed by gender.Methods: We followed 602,242 participants (49% men), aged 19 to 67 years at enrollment from four Norwegian health surveys carried out between 1972 and 2003, by linkage to Norwegian national registries through December 2007. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated by fitting Cox proportional hazard models and adjusting for relevant confounders. Heterogeneity by gender in the effect of smoking and risk of rectal cancer was tested with Wald χ2.Results: During a mean follow-up of 14 years, 1,336 men and 840 women developed invasive rectal cancer. Ever smokers had a significantly increased risk of rectal cancer of more than 25% for both men (HR = 1.27, 95% CI = 1.11-1.45) and women (HR = 1.28, 95% CI = 1.11-1.48) compared with gender-specific never smokers. Men smoking ≥20 pack-years had a significantly increased risk of rectal cancer of 35% (HR = 1.35, 95% CI = 1.14-1.58), whereas for women, it was 47% (HR = 1.47, 95% CI = 1.13-1.91) compared with gender-specific never smokers. For both men and women, we observed significant dose-response associations between the risk of rectal cancer for four variables [Age at smoking initiation in years (both ptrend <0.05), number of cigarettes smoked per day (both ptrend <0.0001), smoking duration in years (ptrend <0.05, <0.0001) and number of pack-years smoked (both ptrend <0.0001)]. The test for heterogeneity by gender was not significant between smoking status and the risk of rectal cancer (Wald χ2, p -value; current smokers = 0.85; former smokers = 0.87; ever smokers = 1.00).Conclusions: Smoking increases the risk of rectal cancer to the same extent in women as in men. [ABSTRACT FROM AUTHOR]