Asbestos exposure interacts with smoking, genetics to raise IPF risk
Workplace exposure to asbestos alone was not linked to increased disease risk
Being exposed at work to medium or high levels of asbestos is associated with a near double risk of developing idiopathic pulmonary fibrosis (IPF) for cigarette smokers, according to a recent U.K. study involving men.
The association between asbestos, smoking, and IPF was especially strong in people with a genetic predisposition toward developing IPF. The study found that asbestos exposure alone, without other risk factors like cigarette smoking or genetics, is not tied to an increased risk of IPF, however.
“These findings indicate that, at least in UK men, there is no overall association between occupational asbestos exposure alone and risk of IPF,” the researchers wrote in the study, “What role for asbestos in idiopathic pulmonary fibrosis? Findings from the IPF job exposures case–control study,” which was published in Occupational & Environmental Medicine.
The causes of IPF remain poorly understood, though several risk factors have been identified. Certain genetic mutations have been linked to an increased risk of developing the disease and exposure to toxins that can damage lung tissue, such as cigarette smoke, also may increase the risk.
Asbestos exposure and smoking, genetic predisposition to IPF
Asbestos is a mineral used in building materials for many decades. Tiny crystals of asbestos can easily get into the air, and breathing them can cause lung damage. Asbestos exposure has been closely linked to certain lung diseases like cancer, but the connection between asbestos exposure and IPF remains incompletely researched, leading a research team led by scientists at Imperial College London to conduct a case-control study (NCT03211507) involving 494 men with IPF and 466 men similar in age who didn’t have lung disease. About three-quarters of the men in both groups had a history of smoking.
“The study was limited to men to increase [statistical] power because men more often have occupational asbestos exposure than women,” the researchers wrote.
Based on interviews, the researchers quantified participants’ asbestos exposure over their lifetime. About two-thirds of participants in both groups were exposed to medium to high levels of asbestos, with roughly 8% in each group having high exposure, based on these estimates.
“The majority of men in their 70s in the UK who attend hospital with IPF have worked for prolonged periods in high or medium risk asbestos exposure jobs,” the researchers wrote.
The scientists constructed statistical models to compare the risk of IPF based on asbestos exposure. In these models, exposure to asbestos alone wasn’t found to be associated with an increased risk.
Smoking was associated with a significantly 40% higher IPF risk, however. The models also showed a significant interaction between smoking and asbestos exposure. In other words, the risk of IPF was significantly increased in patients who both smoked and had been exposed to asbestos. The risk was nearly doubled in patients with a history of smoking and medium or high asbestos exposure.
This association was particularly strong in those carrying a particular genetic variant in the MUC5B gene, called rs35705950, which has been associated with an increased IPF risk in previous studies. Among those carrying at least one copy of this genetic variant, those with a history of smoking and asbestos exposure had a more than five times higher risk of IPF. No significant association between smoking and asbestos exposure was found for those without this variant.
“After stratifying for genotype [genetic background], we found a significant three-way interaction between having ever smoked and having ever worked for at least a year in a high/medium asbestos exposure risk job … for carriers of the [variant] of MUC5B rs35705950,” the researchers wrote.
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