Allergic diseases and risk of hematopoietic malignancies in a cohort of postmenopausal women: a report from the Iowa Women's Health Study.

BACKGROUND: Allergic diseases signify immune dysregulation attributable to underlying genetics and environmental exposures. Associations between various allergies and hematopoietic cancers have been observed, albeit inconsistently; however, few prospective studies have examined the risk, and even fewer among older adults.
METHODS: We examined risk of incident hematopoietic cancers in those reporting allergic diseases in a population-based cohort of 22,601 older women (Iowa Women's Health Study). Self-reported allergic status, including asthma, hay fever, eczema, and/or other allergies, was determined via questionnaire in 1997 (mean age, 72 years; range, 63-81 years). Incident cancers were ascertained by linkage with the Iowa Cancer Registry from 1997 to 2011. Cox proportional hazards regression was performed to estimate multivariate-adjusted HR and 95% confidence intervals (CI) for myeloid (N = 177) and lymphoid (N = 437) malignancies, respectively.
RESULTS: Allergic diseases were not associated with risk of myeloid (HR, 1.00; 95% CI, 0.72-1.37) or lymphoid (HR, 0.99; 95% CI, 0.81-1.22) malignancies overall, or for most allergic and malignant subtypes examined. Self-reported asthma was positively associated with development of myelodysplastic syndrome (MDS; HR, 2.00; 95% CI, 0.93-4.32). In addition, there was a 30% to 40% decrease in risk of both lymphoid and myeloid cancers in those reporting rural residences but no association in those reporting urban residences; the interaction between residence and allergy was statistically significant for lymphoid malignancies (Pinteraction = 0.05). CONCLUSIONS AND IMPACT: These results suggest that asthma may contribute to the pathogenesis of MDS, a finding consistent with the chronic antigen stimulation hypothesis. Susceptibility differences by location of residence are concordant with the hygiene hypothesis and merit additional exploration. ©2014 American Association for Cancer Research.