In a recent study published in the journal Scientific Reports, researchers examined the association between adherence to a Western-style dietary pattern and the likelihood of asthma and its symptoms among children and adolescents in Yazd, Iran.

Study: Association between a western diet and asthma among children and adolescents. Image Credit: Artur_eM / Shutterstock

Background 

Asthma is a chronic inflammatory disease with genetic and environmental factors. Globally, asthma’s burden on patients and healthcare systems is increasing, causing about 15 million disability-adjusted life years lost annually. Around 300 million people have asthma, with prevalence rising. Though more common in high-income countries, low-income countries are also affected. Childhood asthma prevalence is 10.1% in Brazil, 5.35% in India, 10.6% in Oman, and 6% in Iran. Risk factors include no breastfeeding, socioeconomic status, infections, and dietary intake. Further research is needed to confirm the relationship between a Western dietary pattern and childhood asthma, particularly in the Middle East, where dietary habits are rapidly changing.

About the study 

The present cross-sectional study was conducted in early 2020 as part of the Global Asthma Network (GAN). Using cluster sampling, 7214 children (6-7 years) and 3026 adolescents (13-14 years) from 36 elementary and 48 high schools participated, achieving 71.3% and 83.5% response rates, respectively. Due to the coronavirus disease 2019 (COVID-19), data collection involved online questionnaires about asthma symptoms, risk factors, and dietary intake supplemented by pre-pandemic paper questionnaires.

The GAN questionnaire, derived from the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, assessed asthma symptoms and dietary intake over the last 12 months. A pilot study confirmed its reliability (Cronbach’s alpha: 0.862). A Western dietary pattern score was calculated based on the consumption of nine food groups, and participants were categorized into tertiles.

Data on height, weight, ethnicity, and screen time were also collected, with body mass index (BMI) calculated from weight and height. Statistical analyses used STATA software, employing chi-square tests, t-tests, and logistic regression to explore associations between Western dietary patterns and asthma outcomes, adjusting for confounders. The study adhered to ethical guidelines, with approval from Shahid Sadoughi University’s (SSU’s) ethics committee and informed consent from participants.

Study results 

The study included 7,667 participants, examining asthma-related characteristics confirmed by a doctor and medication-prescribed asthma. Among the 324 participants with doctor-confirmed asthma, 58.02% were boys, and 61.7% of those with medication-prescribed asthma were also boys. Children with doctor-diagnosed asthma were older than those without asthma, and this was similarly observed in those with medication-prescribed asthma. There were significant differences in ethnicity distribution between children with and without medication-prescribed asthma. The history of wheezing and recent wheezing episodes were notably lower in children with doctor-diagnosed asthma compared to those without, and these differences were significant in children with medication-prescribed asthma.

Nine food items were used to assess the Western dietary pattern score, revealing that the intake frequency of fast foods, soft drinks, and sauce was significantly higher in children with doctor-diagnosed asthma compared to those without the disease. Similarly, children using asthma medication had higher intake frequencies of margarine, fast foods, and sauce compared to those not using medication.

The study investigated the association between adherence to a Western dietary pattern and doctor-confirmed asthma, finding a decreasing trend but no significant association across girls, boys, and the entire population. No significant association was found between adherence to a Western dietary pattern and the odds of current asthma in girls or the entire population. However, a significant negative trend was observed in boys, which remained significant after adjusting for BMI, television watching, and computer use.

Adherence to a Western dietary pattern was not significantly related to the use of asthma medications in the entire population or in subgroup analyses by sex. In boys and the whole population, higher adherence to a Western dietary pattern was associated with an increased risk of wheezing in the past 12 months compared to those with lower adherence. After adjusting for age and sex, this relationship remained significant for the whole population, with children in the top adherence tertile having a 24% higher chance of developing wheezing in the past 12 months compared to those in the lower tertile. However, this association disappeared for boys after adjusting for age and sex.

Conclusions 

To summarize, this study found a significant positive association between adherence to a Western dietary pattern and wheezing in the past 12 months among all participants and boys. However, it remained significant only in boys after adjusting for confounders. Other studies have linked Western diets to wheezing, which is consistent with these results. However, no association was found between adherence to a Western diet and wheezing in girls. The study found no significant association between a Western dietary pattern and current asthma, doctor-confirmed asthma, or use of asthma medication.