Early exposure to sunlight and allergic morbidity: The PARIS birth cohort.
Level 3 - non-randomized controlled study
Prospective cohort study
PubMed 38636876 · doi:10.1016/j.scitotenv.2024.172543
What was done
Researchers examined the relationship between early solar radiation exposure and allergic morbidity in the PARIS birth cohort. The analysis included children who completed checkups at 18 months (n = 2012) and/or 8-9 years (n = 1080). Solar radiation, temperature, and relative humidity were derived from meteorological data, and longitudinal cluster analysis was used to define exposure trajectories. Multivariable logistic regression models evaluated associations with allergic sensitization (at 18 months and 8-9 years) and current asthma, rhinitis, and eczema (at 8-9 years), adjusting for confounders and testing for effect modification by maternal vitamin D supplementation.
What was found
Four exposure trajectories were identified. Children in the highest early solar radiation trajectory had a borderline reduced risk of sensitization at 8-9 years compared with the lowest trajectory (p = 0.06), which reached statistical significance in children whose mothers took vitamin D supplements. Per interquartile range (IQR) increase, prenatal solar radiation was associated with decreased odds of sensitization (aOR 0.47, 95% CI 0.25-0.87) and asthma (aOR 0.32, 95% CI 0.1-0.96) at 8-9 years. Postnatal solar radiation was also associated with lower sensitization risk at 8-9 years (aOR 0.84 per IQR increase, 95% CI 0.7-1.00).
Why it matters
These findings suggest that prenatal and early-life sunlight exposure, particularly alongside maternal vitamin D supplementation, may offer protection against childhood allergic sensitization and asthma.
Limits
Exposure was estimated using ambient meteorological data rather than individual UV dosimeters or recorded time spent outdoors. There was substantial cohort attrition between 18 months (n = 2012) and 8-9 years (n = 1080). Residual confounding from physical activity, air pollution, and other lifestyle factors remains possible, and biological vitamin D levels were not reported.
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