Second-Hand Smoke during Childhood Linked to Higher Breast Cancer Risk in Women

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Post last modified:July 28, 2023

Second-Hand Smoke during Childhood Linked to Higher Breast Cancer Risk in Women: A Closer Look at the Norwegian Women and Cancer Study

Introduction

Breast cancer is a significant health concern affecting women worldwide. While several risk factors have been identified, the association between second-hand smoke (SHS) exposure during childhood and breast cancer risk has been a topic of ongoing research. A recent study conducted by Inger T Gram and team from University of Tromsø (UiT) Norway, sheds light on this matter, providing valuable insights into the potential impact of parental SHS exposure during childhood on breast cancer risk. In this blog, we dive into the details of the Norwegian Women and Cancer Study, explore the findings, and discuss the implications of these results for breast cancer prevention.

The Norwegian Women and Cancer Study

This study is aimed at understanding the risk factors for cancer in women. Between 1991 and 2007, 45,923 never-smoking women aged 34 to 70 years participated in the study by completing a baseline questionnaire. These women were then followed up over an average period of 19.8 years, with data obtained through linkages to national registries until December 2018.

Examining the Relationship between SHS and Breast Cancer Risk

One of the primary objectives of the study was to investigate whether exposure to SHS during childhood, particularly from parents, had any influence on the overall risk of breast cancer. Researchers utilized Cox proportional-hazards models, a statistical method for survival analysis, to estimate age-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) to assess the association between SHS exposure and breast cancer risk.

Findings of the Study

The results of the Norwegian Women and Cancer Study revealed a noteworthy link between SHS exposure during childhood and breast cancer risk in never-smoking women. Specifically, women who had been exposed to SHS from their parents during childhood exhibited an 11% higher risk of developing invasive breast cancer compared to those who were not exposed. This finding suggests that SHS exposure during childhood could be a potential risk factor for breast cancer later in life.

Subtypes of Breast Cancer and SHS Exposure

To gain a deeper understanding of the relationship between SHS exposure and breast cancer, the researchers examined whether the risk varied based on the receptor status of the tumor. Hormone receptor status is an essential characteristic of breast cancer, as it influences treatment options and disease progression.

The study findings showed no significant difference in breast cancer risk associated with SHS exposure when analyzed based on estrogen and progesterone receptor status. This indicates that SHS exposure during childhood may not influence the likelihood of developing specific subtypes of breast cancer.

Estimating the Impact of Parental SHS Exposure on Breast Cancer Incidence

To quantify the potential impact of parental SHS exposure during childhood on breast cancer incidence, the researchers calculated two essential metrics: the attributable fraction and the population attributable fraction. These metrics help estimate the proportion of breast cancer cases that could be attributed to parental SHS exposure and the proportion in the overall population, respectively.

The results indicated that approximately 1 in 14 breast cancer cases (10.3%) among never-smoking women could have been avoided in the absence of SHS exposure from parents during childhood. Additionally, the population attributable fraction, which provides an estimate of the burden of disease in the entire population, was found to be 7.0%. This suggests that the impact of SHS exposure on breast cancer incidence may be more significant than previously believed.

Implications for Breast Cancer Prevention

The findings of the Norwegian Women and Cancer Study hold vital implications for breast cancer prevention efforts. While the study focused on never-smoking women and SHS exposure during childhood, it highlights the importance of minimizing exposure to second-hand smoke in general.

Public health initiatives aimed at reducing SHS exposure in homes, workplaces, and public spaces can play a crucial role in breast cancer prevention. Furthermore, creating awareness about the potential risks of SHS exposure during childhood can empower parents to take proactive steps to protect their children from the harmful effects of passive smoking.

Conclusion

The Norwegian Women and Cancer Study provides valuable evidence of a potential link between SHS exposure during childhood and an increased risk of breast cancer in never-smoking women. These findings underscore the need for continued efforts to raise awareness about the health risks associated with second-hand smoke and the importance of implementing policies and interventions to reduce exposure. By taking proactive steps to minimize SHS exposure, we may be able to prevent a considerable number of breast cancer cases and improve the overall health and well-being of women everywhere.