Clinicians should be mindful of the transition from chronic rhinosinusitis to new onset asthma, while figuring out ways to prevent it.

“The clinical observation that chronic rhinosinusitis (CRS) and asthma commonly co-occur has been long known,” explains Brian S. Schwartz, MD, MS. “This is thought to be due to shared inflammation in contiguous airways.” According to Dr. Schwartz, however, no studies have employed the large sample sizes necessary to formally examine whether preexisting CRS is potentially causally linked with new onset asthma over time.

Dr. Schwartz and colleagues conducted a study, published in Allergy, to determine whether CRS is documented in patients without asthma and then assess the risk for new onset asthma in the following years. “This is the first step in developing new approaches for such patients, because if this risk is present over time, treatment for CRS could prevent the new onset of asthma,” Dr. Schwartz says.

The study team used a large patient sample gathered from EHRs dating from 2008 to 2019. “[Our study] required a large patient sample since we have to remove all people with prevalent asthma from the analysis,” Dr. Schwartz explains, adding that there were more than 43,000 such patients. They conducted a retrospective cohort study of people with and without CRS and looked for the new development of asthma over time, comparing more than 35,000 patients who developed asthma with more than 890,000 who did not.

Younger Women More Likely to Have New Onset Asthma

To adjust for confounding variables (eg, contact with the health system, sociodemographic, comorbidities), the researchers used complementary log-log regression.

The study team hypothesized that CRS based on diagnoses would have higher sensitivity in case finding, and that CRS based on sinus CT scans would have higher specificity. “We identified new onset asthma with diagnoses or medications for asthma in [people] who did not previously have a record of either,” Dr. Schwartz says. “We observed that both methods of identifying CRS were associated with increased risk for new onset asthma, with a 1.5-fold increased risk for CRS based on diagnoses and 2.2-fold increased risk for CRS based on positive sinus CT scans.” Both CRS definitions were linked (HR, 95% CI) with new onset asthma, with 2.21 (1.93-2.54) and 1.48 (1.38-1.59) for CRS based on sinus CT scans and two diagnoses, respectively.

Individuals with new onset asthma tended to be female (69.6%) and younger (mean [SD] age 45.9 [17.0]), the researchers note. New onset asthma was uncommonly observed in people with a history of sinus surgery.

Future Research Should Seek Ways to Prevent Asthma Onset

“We found that the elevated risk for new onset asthma after CRS diagnosis persists for over 6 years (Table)” Dr. Schwartz says. “We were worried that the increased risk could be due to more careful case finding for asthma after a diagnosis of sinus disease. However, the fact that the elevated risk persists for much longer suggests that the associations are not due to this concern.”

Dr. Schwartz and colleagues concur that people with CRS can develop new onset asthma over time. “The elevated risk is more than two-fold for CRS based on sinus CT scan,” Dr. Schwartz notes. “Clinicians should be vigilant about this transition—many already are—and we should figure out how to prevent it if possible.” Therefore, he adds, the next logical step is to conduct prospective studies to determine whether, and how, treatment of CRS could prevent the onset of asthma.