D2.483 - Outdoor Activity and Screen Time at Age 3 years and Allergic Symptoms at Age 6 years: A Nationwide Birth Cohort Study (JECS)

Physical activity in early childhood is encouraged; however, recent trends indicate a decline in outdoor activity and an increase in sedentary behaviors, such as excessive screen exposure. While associations between outdoor activity or screen time and asthma have been reported, evidence regarding eczema and rhinitis remains limited.

We analyzed data from the Japan Environment and Children’s Study (JECS), a nationwide birth cohort. Outdoor activity and screen time at age 3 were assessed using caregiver-reported questionnaires. Outcomes included current wheeze, eczema, and rhinitis at age 6, assessed using questionnaires based on the International Study of Asthma and Allergies in Childhood (ISAAC). Binary logistic regression model was applied for analysis. Sleep disturbance related to symptoms was additionally examined among children with wheeze or eczema. For sleep disturbances, multinomial logistic regression model was used. Odds ratios (OR) and 95% confidence intervals (CI) were estimated after adjusting for relevant covariates.

A total of 63,080 children were included. At age 6, wheeze was reported in 6,156 children (9.8%), eczema in 10,213 (16.2%), and rhinitis in 25,026 (39.7%). No clear associations were observed between outdoor activity or screen time and wheeze. For eczema, compared with ≥2 hours(h)/day of screen time, 1–2 h/day and <1 h/day were associated with slightly lower odds (adjusted OR [aOR] 0.95, 95% CI 0.90–1.00; and 0.93, 95% CI 0.88–0.99, respectively). Among children with eczema, ≥3 h/day of outdoor activity was associated with increased odds of sleep disturbance (aOR 1.27, 95% CI 1.08–1.45 for less frequent disturbance; aOR 1.51, 95% CI 1.04–2.20 for frequent disturbance), and no significant associations were observed for 1-3 h/day. For rhinitis, ≥3 h/day of outdoor activity was associated with a slightly higher risk compared with <1 h/day (aOR 1.07, 95% CI 1.00–1.14), whereas no clear association was observed for 1–3 h/day. Shorter screen time was consistently associated with lower odds of rhinitis compared with ≥2 h/day (1–2 h/day: aOR 0.93, 95% CI 0.90–0.977; <1 h/day: aOR 0.93, 95% CI 0.89–0.98).

Outdoor activity and screen time at age 3 showed limited associations with wheeze at age 6. Shorter screen exposure was modestly associated with lower odds of eczema and rhinitis. Among children with eczema, longer outdoor activity may be associated with increased sleep disturbance related to symptoms.