Allergies Linked to Lower Lung Cancer Risk, New Study Finds

Could your allergies be protecting you? This large study found a surprising link between common allergies and a reduced risk of lung cancer, especially in men and people with allergic rhinitis.

In a recent study published in Frontiers in Medicine, researchers examined the relationship between allergic diseases and the risk of developing lung cancer.

Allergies and cancer are increasingly recognized as significant public health problems in both developing and developed countries. Lung cancer is one of the most common cancers worldwide, with approximately 2.26 million cases reported in 2019. The number of lung cancer cases and deaths increased by 26% and 20%, respectively, between 2010 and 2019. At the same time, the number of disability-adjusted life years (DALYs) associated with lung cancer increased by 16%.

Link between allergic diseases and lung cancer risk

The association of allergic diseases with lung cancer risk varies depending on the type of allergy. For example, having asthma is associated with an increased risk of lung cancer, whereas having allergic rhinitis (AR) or eczema may reduce this risk. Asthma, although an allergic disease, was intentionally excluded from this meta-analysis to ensure methodological homogeneity and prevent bias, as it is known to increase the risk of lung cancer.

One hypothesis is that allergies may reduce the risk of lung cancer by enhancing immunoglobulin E (IgE)-mediated immune surveillance, which may help destroy early-stage malignant cells. In contrast, another hypothesis suggests that chronic immune stimulation may lead to random mutations in rapidly dividing cells, increasing cancer risk.

The authors also note that allergic reactions may play a dual role: being harmful at primary sites of inflammation but potentially protective at distant sites. The integrative hypothesis proposes that the interplay of immune surveillance, chronic inflammation, and immune bias underlies the association between allergies and cancer. These hypotheses provide different insights into the complex relationship between allergy and cancer. Despite growing interest, considerable uncertainty and controversy remain regarding the specific associations between AR, eczema, and lung cancer risk.

Research and results

In the present study, the researchers conducted a meta-analysis of the associations between AR and eczema with the risk of lung cancer. First, a systematic literature search was conducted in the Web of Science, Embase, Cochrane Library, and PubMed databases to identify relevant studies. Case-control or cohort studies assessing the association between allergic diseases and the risk of lung cancer were included in the meta-analysis.

Relevant data including study design, geographic region, participant characteristics and outcomes were extracted from the selected publications. The Newcastle-Ottawa Scale was used to assess the quality of the studies and studies were classified as having low, moderate or high quality.

The analysis showed that allergic diseases were inversely associated with the risk of lung cancer. Despite considerable heterogeneity between studies, sensitive analyses showed that no single study significantly affected the overall effect size, supporting the robustness of the results.

The meta-analysis included 10 studies: eight case-control studies and two cohort studies, comprising over 3.8 million participants. Sample sizes ranged from 302 to 1.74 million people. Diagnoses of AR and eczema were made by measuring serum IgE levels or questionnaires. Lung cancer was diagnosed by histology or using ICD-9 or ICD-10 codes.

Three studies were rated as moderate quality, seven as high quality. The meta-analysis found that allergic diseases were inversely associated with the risk of lung cancer.

Key findings

• Allergic rhinitis was associated with a 26% reduction in the odds of developing lung cancer (OR 0.74; 95% CI: 0.64–0.86).
• Eczema did not show a statistically significant association (OR 0.73; 95% CI: 0.51–1.06).
• In men, allergic diseases were associated with a 44% reduction in the risk of lung cancer, and in women, with a 29% reduction.
• Seven studies conducted in the Americas found a negative association between AR and lung cancer risk, but eczema did not show a significant association.

Conclusion

A meta-analysis found that people with allergies were a quarter less likely to develop lung cancer than those without allergies. The association was particularly strong in men and in American populations. Although eczema was not associated with a reduced risk overall, a negative association was observed in men.

Limitations of the study include small sample sizes in some studies, limited applicability of the results due to the predominance of American participants, and potential bias associated with the use of self-reported diagnoses.