Cold temperatures may worsen asthma symptoms in children

Key takeaways:

• Nasal oxidative stress may be a contributor to worsening asthma symptoms.
• Nasal malondialdehyde levels could be important indicators of cold air and pollution effects on asthma.

Biomarkers — such as nasal fluid, saliva and urine samples — can be used to explain the connection between cold temperatures, oxidative stress and asthma flare-ups, according to a study published in Pediatric Research.

“This study builds on our previous research,” Linchen He, PhD, MA, MEM, assistant professor, department of community and population health at Lehigh University College of Health and first author of the study, told Healio.

“Our earlier findings showed that exposure to lower temperatures during cold seasons was associated with increased asthma symptoms in children. These results prompted us to investigate the biological mechanisms behind this relationship in the current study,” He said.

Methods

The study recruited 43 children (mean age, 7.8 years; 40% girls) aged 5 to 13 years diagnosed with mild or moderate asthma from a hospital in Shanghai. Each child had to have experienced at least one asthma exacerbation within the past year.

Between Feb. 14 and April 14, 2017, each child had four clinical assessments at 2-week intervals collecting nasal fluid, urine and saliva. Malondialdehyde (MDA) levels were measured in these fluids as a biomarker of oxidative stress in the nasal cavity, the circulatory system and the oral cavity.

Additionally, urinary 8-hydroxy-2’-deoxyguanosine, a stable product of DNA oxidate damage, was measured as a biomarker of systemic oxidative stress, and urinary 6-sulfatoxymelatonin was measured as a surrogate of circulating melatonin.

During each assessment, researchers used impulse oscillometry as well as the CACT questionnaire to further collect data about asthma symptoms.

Results

Among the 43 participants, 13 (30%) reported eosinophilic inflammation. From a total of 172 visits, 64 children (37%) had a respiratory tract infection, 49 (29%) had used nasal steroids and seven (4%) had an asthma exacerbation.

Researchers found significant associations between 2°C decrements in personal temperature exposures averaged over 12 hours, 24 hours, 1 week and 2 weeks prior to an assessment and higher nasal and urinary MDA concentrations by 47% (95% CI, 28%-68%), 62% (95% CI, 43%-84%), 60% (95% CI, 40%-82%) and 77% (95% CI, 49%-110%), respectively.

A significant association was also found between a 2°C decrement in personal temperature exposure averaged over 1 week and 2 weeks prior to assessments and 9.3% (95% CI, 0.2%-19%) and 14% (95% CI, 2.6%-27%) higher urinary MDA concentrations, respectively.

Exposure to lower temperatures (2°C, 12-hour average) was consistently associated with higher airway impedance by 2.8%, higher total airway resistance by 2.6%, higher large airway resistance by 1.6%, higher small airway resistance by 4.7%, and higher airway reactance by 13.6% for reactance at 5 Hz and by 3.1% for airway reactance.

“While it’s known that cold air can worsen asthma symptoms, the biological processes behind this effect have not been well understood,” He said. “Our findings suggest that nasal oxidative stress may be a link between exposure to cold temperatures and increased asthma symptoms. This is the first study to identify this potential connection.”

The 2-week average temperature exposure had the strongest nasal MDA association, whereas Childhood Asthma Control Test (CACT) scores showed decreases that were associated with colder temperatures mediated by nasal MDA.

Nasal MDA’s mediations on the total effects of temperature exposure on individual CACT scores included on average 34% (P = .02) for physical activity limitations, 57% of coughing and 36% (P = .022) of child-reported total CACT scores.

“Exposure to lower temperatures during cold seasons was strongly linked to increased oxidative stress in the nasal passages,” said He. “Our results firstly suggest a plausible pathway that colder temperature exposure worsens pediatric asthma symptoms partly via inducing oxidative stress in the nasal cavity.”

He further stated that in another previous study, ,” the use of nasal MDA was first introduced as a biomarker of nasal oxidative stress.

“We found that nasal MDA levels increased in response to higher exposure to air pollutants, ie, fine particulate matter and ozone,” he said. “It’s well-established that both air pollution and cold air can trigger asthma exacerbations and worsen symptoms. Our findings with nasal MDA now provide a potential biological link for these effects.”

He and colleagues recommend further research into how MDA could be effectively incorporated into asthma management strategies.
He said.

References:

• He L, et al. Environ Sci Technol. 2020;doi:10.1021/acs.est.0c02558.
• He L, et al. PLoS One. 2023;doi:10.1371/journal.pone.0293603.