Patients with interstitial lung disease (ILD) subtypes, including idiopathic pulmonary fibrosis (IPF), tend to have inhalational exposures more than half of the time, with a higher risk in male individuals and patients with a family history of ILD, according to a study recently published in Respirology.

The study identified the baseline characteristics of almost 4000 patients with ILD-related inhalational exposures retrieved from the Canadian Registry for Pulmonary Fibrosis. The goal was to characterize the associations between pulmonary functions, exposures, and survival in patients with fibrotic ILD.

The patients completed questionnaires concerning their occupational and environmental exposures, emphasizing regular and repeated exposure within 3 years prior to symptom onset for local exposures and lifetime exposure history for occupational exposures.


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“Overall, 2385 patients (62%) reported any environmental or occupational exposure. Mold (38%) and bird (37%) were the most common exposures, with asbestos and other inorganic dust exposures present in 12% and 17% of patients, respectively,” the authors wrote.

Read more about IPF epidemiology

The study also established a varying effect of exposure on pulmonary function in different ILD subtypes.

“In hypersensitivity pneumonitis (HP) particularly, patients with a known exposure had a slower [forced vital capacity] decline compared to patients without a known exposure; this effect was not seen in other diagnoses with the exception of unclassifiable ILD and history of inorganic exposure,” the authors explained, adding that patients with IPF showed the greatest prevalence of inorganic exposure at 10%.

Moreover, there were higher odds of exposure in all ILD subtypes when there was a family history of ILD, and patients with IPF were the youngest across all subtypes. Improved survival was related to a history of exposure, and organic exposure had enhanced transplant-free survival in patients with HP.

Inhalational exposures can cause ILD, but not much information is available concerning ILD subtypes and their relationships with survival and pulmonary function. The conclusions in the study imply that inhalational exposures may harbor a risk for all ILD diagnoses and contribute to the initiation and progression of the disease. 

Further studies require control groups to expose a tighter association between exposure and ILD incidence. This study design may deliver more knowledge on precise exposure-disease phenotypes and shed light on the final clinical implications.

Reference

Lee CT, Strek ME, Adegunsoye A, et al. Inhalational exposures in patients with fibrotic interstitial lung disease: presentation, pulmonary function and survival in the Canadian Registry for Pulmonary Fibrosis. Respirology. Published online May 5, 2022. doi:10.1111/resp.14267