Birth season associated with asthma, allergic rhinitis

Key takeaways:

• People born in the summer season had the lowest risk for developing asthma or allergic rhinitis.
• Those born in the fall or winter bore the highest risk for asthma and allergies.

People born in fall and winter months in Finland were more likely to develop asthma and allergic rhinitis vs. those born in spring and summer, according to a study published in Allergy.

“The study aimed to explore the link between season of birth and the risk of airway allergies and respiratory diseases, building on prior research showing higher asthma risk for those born in winter or spring in Finland,” Sanna Toppila-Salmi, MD, PhD, professor of otorhinolaryngology at the University of Eastern Finland and director of the Airway Research Group, Inflammation Center at the Division of Allergy, Helsinki University Hospital, told Healio.

Sanna Toppila-Salmi

This randomly sampled retrospective study analyzed data between 2005 to 2019 from 74,868 patients (mean age, 34.53 years; age range, 0-102 years; 48.7% male) with otorhinolaryngological and respiratory diagnoses at the Hospital District of Helsinki and Uusimaa. Researchers collected data on the birth date, sex, visit date and comorbidities, including NSAID-exacerbated respiratory disease (N-ERD), asthma, allergic rhinitis (AR), chronic rhinosinusitis with nasal polyps, and chronic rhinosinusitis without nasal polyps (CRSsNP).

Four groups were formed based on season of birth. The proportion of asthma in the four groups was 43.1%, 42.1%, 41.1%, 42.7% in winter, spring, summer and fall, respectively. The proportion of AR was 12.6%, 12%, 10.7%, 12.1%, respectively.

Researchers found a statistically significant association between being born in winter or fall and having AR (P < .0 for both) or asthma (P < .0 and P = .003, respectively). They also found that those born in the spring also had an association with having AR (P < .0).

Adjusted models showed no significant associations between seasons of birth and CRSsNP, CRSwNP, N-ERD or NAR, which the researchers said warrants further studies.

“A key finding was that being born in autumn or winter was linked to a higher incidence of asthma and allergic rhinitis, while those born in summer had the lowest risk,” Toppila-Salmi explained. “The results are significant because they may indirectly show that environmental factors, such as variation in daylight, allergens, infections and other factors, present at gestational (intrauterine) time or at the newborn’s early life, may influence the risk of developing asthma or allergies later in life.”

She further explained that these findings can help doctors inform and follow up with families that may have a higher risk for developing asthma and allergies.

“They can study early life pathomechanisms of asthma and allergies and invent better treatment and prevention of these diseases,” Toppila-Salmi said. “Doctors can also focus on preventive measures like vitamin D supplementation.”

Public health policies could also emphasize prenatal and early life care and vitamin D supplementation, Toppila-Salmi told Healio. Future research could focus on how these seasonal effects apply in different climates and populations.