Individuals Born in Autumn or Winter More Likely to Develop Asthma, Allergic Rhinitis

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According to research published in Clinical and Translational Allergy, the season in which someone is born—notably autumn and winter—is associated with asthma and allergic rhinitis in people who live in Finland. Additionally, being born in the summer was associated with the lowest incidence of asthma and allergic rhinitis.¹

After prior research suggested that being born in winter or spring was associated with adult-onset asthma, the investigators of the current population-based study evaluated whether season of birth in Finland is associated with airway allergy and other related diseases, such as asthma, non-steroidal anti-inflammatory drug (NSAID) exacerbated respiratory disease (N-ERD), allergic rhinitis, nonallergic rhinitis, chronic rhinosinusitis with nasal polyps (CRSwNP), and CRS without nasal polyps (CRSsNP). The participants were randomly sampled from a retrospective registry of follow-up data from 74,868 patients who visited the Hospital District of Helsinki and Uusimaa in Finland from 2005 to 2019. Patients’ date of birth, sex, date of visit, and comorbidities were collected from this record.²

The participants were organized into groups based on their respective season of birth, and the investigators assessed the proportion of patients in each group who had asthma or other related diseases. The proportion of patients with asthma was highest in the winter and autumn groups (43.1% and 42.7%, respectively), with the spring and summer groups (42.1% and 41.1%, respectively) showing slightly lower proportions of asthma incidence. Additionally, allergic rhinitis was also more prevalent in the winter and autumn groups (12.6% and 12.1%, respectively) compared with the spring and summer groups (12.0% and 10.7%, respectively). There were no significant associations observed in CRS (winter: 9.1%; spring: 9.5%; summer: 9.0%; and autumn: 8.7%), N-ERD (winter: 1.5%; spring: 1.4%; summer: 1.3%; and autumn: 1.5%), or nonallergic rhinitis.²

“When using summer as a reference, we found that being born in any other time of the year was significantly associated with allergic rhinitis, and that being born in autumn or winter was associated with asthma. However, we did not find a statistically significant association of season of birth with chronic rhinosinusitis or N-ERD,” Sanna Salmi, professor of otorhinolaryngology at the University of Eastern Finland, said in a news release.¹

According to the investigators, the findings suggest that early life immunological events may have a role in the pathogenesis of asthma along with other allergic airway diseases. The investigators hypothesize that the association of birth season with airway allergies and related diseases may be influenced by vitamin D metabolism, vegetation and air pollution, and seasonal variation in light levels, all of which can affect allergenicity and immunological responses. In addition, these factors can also impact the risk of allergic rhinitis onset.^1,2

Further, the investigators note that there are possible limitations to the study, including the enrolled study sample possibly not fully representing an entire population and potential gaps in diagnoses in the electronic health record that was used. In addition, the data were also missing information on the onset of patients’ diseases, socioeconomic status, and race, all of which could have mitigations on the findings. They urge that future research is conducted to further assess the potential associations between season of birth and CRssNP, CRSwNP, N-ERD, and nonallergic rhinitis.²

“Our results may also suggest that the pathogenesis of chronic rhinosinusitis and NSAID-exacerbated respiratory disease is less dependent on these early life events; however, further research in larger cohorts is needed to confirm this,” Salmi said in the news release.¹

REFERENCES

1. University of Eastern Finland. Season of birth is associated with the development of asthma and allergic rhinitis. August 14, 2024. Accessed August 16, 2024. https://www.eurekalert.org/news-releases/1054591

2. Hänninen R, Murtomäki A, Svärd F, et al. Being born in autumn or winter is associated with asthma and allergic rhinitis in Finland. Clin Transl Allergy. 2024;e12383 doi:10.1002/clt2.12383