Association Between Allergy, Asthma, and Cancer: The Japan Public Health Center‐Based Prospective Study

Several epidemiological studies have explored the potential associations between allergy, asthma, and cancer incidence, but the findings remain inconclusive. This study investigates the association between a history of allergy, asthma, and cancer risk in a Japanese population. Data were obtained from the Japan Public Health Center-based Prospective Study (JPHC Study). Participants reported in a self-administered questionnaire whether they had been diagnosed by a physician for allergy, asthma, or both (hereafter referred to as "allergy and/or asthma"). They were followed until December 2013. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for overall and site-specific cancers for allergy, asthma, and combined allergy and/or asthma. Subgroup analyses were performed by smoking status. Among participants, 17,679 cancer cases were identified, and 6.5% reported a history of allergy and/or asthma. A borderline association was observed between allergy and/or asthma and thyroid cancer (HR 1.54, 95% CI 1.00-2.35). Subgroup analysis revealed that men with a history of smoking and allergy and/or asthma had an increased risk of colorectal cancer (HR 1.30, 95% CI 1.03-1.63), while never-smoking women with allergy and/or asthma showed an increased risk of cervical cancer (HR 1.98, 95% CI 1.01-3.86). These findings showed no overall association of allergy, asthma, or their combined exposure with cancer risk in a Japanese population, warranting further investigation.