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Hay fever, animal allergies may reduce pancreatic cancer risk
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Patients with allergies, particularly hay fever or animal allergies, were less likely to develop pancreatic cancer than controls in a recent pooled analysis.
Researchers evaluated data from 10 case-control studies including 3,567 patients with pancreatic cancer and 9,145 controls. All studies were collected via the Pancreatic Cancer Case-Control Consortium and assessed patients’ self-reported allergy history.
A borderline-significant association between allergies and reduced risk for pancreatic cancer was observed in pooled analysis of nine studies. (summary OR=0.79; 95% CI, 0.62-1), with significant heterogeneity (P<.001). Heterogeneity significance was not eliminated after adjustment for study location or design, age of onset and number of allergies queries, and the prevalence of allergies among controls. Individual removal of studies from analysis did not impact heterogeneity, with the exception of one study conducted in Minnesota (summary OR=0.73; 95% CI, 0.64-0.84; P=.23 for heterogeneity).
The impact of specific allergies on pancreatic cancer development indicated significantly reduced risk with hay fever (summary OR=0.74; 95% CI, 0.56-0.96 across six studies) and animal allergies (OR=0.62; 95% CI, 0.41-0.94, four studies). A nonsignificant risk reduction was observed across four studies assessing eczema (OR=0.74; 95% CI, 0.42-1.3), but investigators noted significant heterogeneity (P=.039). No associations were observed between pancreatic cancer risk and asthma (OR=0.91; 95% CI, 0.64-1.3, six studies) or drug allergies (OR=1.1; 95% CI, 0.73-1.6, five studies).
Subgroup analysis according to sex, tobacco use and BMI did not indicate significant differences among patients with any allergies. When age of onset was assessed as a continuous variable, a 3% risk reduction was observed for every 5-year age increase.
“The results … indicate that allergies are associated with reduced risk of pancreatic cancer and that hay fever and allergies to animals have the strongest associations,” the researchers concluded. “It also indicates that large gaps continue to exist in our understanding of the apparently reduced risk for pancreatic cancer associated with allergies. Little information is available on risk in relation to some specific allergies … the timing, number and severity of allergies; or the influence of treatment for allergies.”
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