Associations between alcohol intake, cancer risk, and modifying factors in women: smoking, BMI, and MHT interactions

By Vijay Kumar MalesuReviewed by Lily Ramsey, LLMAug 21 2023

In a recent study published in BMC Cancer, researchers examined the association between moderate alcohol intake and specific cancer risks.

The study explored the modifying effects of menopausal hormone therapy (MHT) use, adiposity, and smoking.

Study: Alcohol consumption and cancer incidence in women: interaction with smoking, body mass index and menopausal hormone therapy. Image Credit: ChristianDraghici/Shutterstock.com

Background

The International Agency for Research on Cancer (IARC) and the World Cancer Research Fund (WCRF) identified a strong correlation between alcohol consumption and cancers such as the oral cavity, pharynx, esophagus, and others, asserting no safe alcohol limit.

Other cancers have inconclusive evidence linking them to alcohol. Although certain cancers have clear associations with alcohol, the specific mechanisms remain largely unknown. Some suggest ethanol's conversion into acetaldehyde as a key factor, while others link higher alcohol consumption with increased sex hormone levels.

The impact of alcohol on cancer may also be influenced by factors like smoking, body mass index (BMI), and MHT use. Previous findings, including those from the Million Women Study, have been inconsistent, and hence, further research into these associations is essential.

About the study

The Million Women Study, a prospective research endeavor initiated in 1998, surveyed women attending breast cancer screenings across 66 centers in England and Scotland.

These women provided data about their lifestyle habits, including alcohol consumption. Participants received subsequent surveys every 3-5 years. They achieved nearly complete follow-up using National Health Service (NHS) data, tracking incidents of the 21 most common cancers.

Their baseline data focused on alcohol intake recorded in 1998. Over 1.3 million eligible women were excluded due to previous cancer diagnoses, lack of alcohol consumption data, or unknown smoking status. The final group, 795,121, was segmented based on weekly alcohol intake.

The study utilized Cox proportional hazard models to estimate cancer risks relative to alcohol consumption, adjusting for location, education, smoking habits, BMI, and physical activity.

Analyses on specific cancers considered additional factors like age at menarche and family history. Alcohol's association with cancer was further explored in subgroups divided by smoking, BMI, and MHT usage.

A key aspect was assessing alcohol's impact on cancers and other risk factors. All analyses were performed using Stata version 17, with two-sided statistical tests.

Study results

In the present study involving 795,121 women with an average age of 56 at recruitment, 92% consumed alcohol below the United Kingdom (UK)'s recommended weekly limit of 14 drinks, and the average intake was 6.7 drinks per week.

Women were tracked over 13.4 million person-years (averaging 16.9 years each), during which 140,203 new cancer cases emerged. The research sought correlations between alcohol intake and specific cancer risks.

Significant associations were observed between increased alcohol consumption and several cancers. Notably, for each additional daily drink, the relative risk (RR) surged for oral cavity, pharynx, larynx, and oesophageal squamous cell carcinoma (OSCC) cancers, resulting in a combined relative risk (RR) of 1.38. Other significant associations with alcohol were found for breast, colorectal, pancreatic, and lung cancers.

Although an elevated risk of liver cancer with alcohol intake was observed, it wasn't statistically significant. Conversely, increased alcohol was associated with decreased risks of thyroid cancer, renal cell carcinoma, non-Hodgkin's lymphoma, multiple myeloma, and oesophageal adenocarcinoma (OAC).

However, the OAC finding might be influenced by uncontrolled confounding factors like gastric reflux, which often leads to reduced alcohol intake and is closely associated with OAC risk. No significant associations with alcohol were found for cancers like bladder, leukemia, cervical, melanoma, endometrial, brain, and ovarian.

An interesting observation was the interaction between smoking and alcohol consumption concerning upper aerodigestive cancer risk. Compared to non-smokers with low alcohol consumption, non-smokers with high alcohol consumption had a 1.33 RR, past smokers 2.06, and heavy-smoking current drinkers had a significant 9.70 RR.

Analyses regarding BMI and MHT use showed no significant variations in alcohol-associated RRs for any cancer.

Among female drinkers in this study, it's estimated that excess alcohol (more than 1-2 drinks weekly) might be responsible for 21% of aerodigestive cancers, 6% of breast cancers, 5% of colorectal cancers, and 3% of pancreatic cancers. The precise number of cases attributed to such drinking patterns would hinge on each cancer's incidence rate.

Discussions

The present comprehensive cohort study focused on middle-aged women; most consumed less than the recommended 14 drinks weekly. The study showed moderate alcohol consumption substantially increased the risk for certain cancers, such as the oral cavity, pharynx, larynx, esophagus, breast, colorectal, and pancreas.

Moderate drinking decreased the risk of thyroid cancer, renal cell carcinoma, non-Hodgkin's lymphoma, and multiple myeloma. Smoking amplified the alcohol-associated cancer risks, especially for upper aerodigestive tract cancers. BMI and MHT usage did not significantly alter the cancer risks related to alcohol consumption.

The study's findings align with prior reviews by IARC and WCRF regarding alcohol-related cancer risks, particularly for oral cavity, pharynx, larynx, and colorectal cancer. However, the study did not identify a significant link between moderate alcohol consumption and liver cancer. This could be due to the moderate alcohol consumption typical of women in this cohort.

Furthermore, the present study explored the interaction between alcohol and smoking, revealing that the harmful effects of alcohol were predominantly seen in heavy smokers, suggesting alcohol exacerbates smoking's adverse effects.

The study's strengths lie in its prospective design, minimal loss to follow-up, and many cases. However, its limitations include potential errors in reporting alcohol intake and the exclusive focus on women.