Circulating vitamin D levels affect the risk for respiratory symptoms related to indoor air pollution among children with obesity and asthma, findings from a recent study suggest.
Asthma, obesity and air pollution disproportionately affect urban minority populations, and rates of vitamin D deficiency are highest among the black pediatric population, according to the researchers. Therefore, in this study, they sought to determine whether personal vitamin D status in a predominantly black urban cohort of children with asthma mitigates the effects of indoor air particulate exposure and whether any differences exist according to obesity status.
The study included 120 children aged 5 to 12 years with asthma (mean age, 9.7 years; 55% boys; 95% black) from Baltimore who were enrolled from the Domestic Indoor Particulate Matter and Childhood Asthma Morbidity (DISCOVER) study from 2009 to 2015. Serum 25-hydroxyvitamin D (25-[OH]D), asthma symptoms and fine particulate matter (PM2.5) exposure during a 7-day period were evaluated at baseline and every 3 months for 9 months. The average BMI across all children was in the 71st percentile and 36% were considered obese. The mean PM2.5 indoor exposure was 38.2 µg/m3 and the mean 25-(OH)D level was 19.1 ng/mL.
Effects of vitamin D levels
Results showed that lower serum 25-(OH)D levels strengthened the adverse association between PM2.5 and limited activity (P for interaction = .003), trouble breathing (P for interaction = .054), feeling bothered by asthma (P for interaction = .03), having any daytime symptoms (P for interaction = .006), nighttime symptoms (P for interaction = .034) and needing rescue medication (P for interaction = .032) in children with obesity.
According to the data, low 25-(OH)D levels increased the adverse effect of PM2.5 on daytime asthma symptoms (ORPM2.5 = 1.26; P = .049 for a vitamin D level of 15.5 ng/mL), and the effect of PM2.5 on daytime symptoms became stronger with decreasing levels of vitamin D less than 15.5 ng/mL. A similar result was seen for the effects of PM2.5 on nighttime symptoms in children with obesity with 25-(OH)D levels less than 16.4 ng/mL.
Conversely, at extreme levels of indoor air particulate pollution, higher levels of vitamin D protected against an increased likelihood for daytime asthma symptoms driven by PM2.5 among children with obesity (ORvitamin D = 0.87; P = .049 at a PM2.5 concentration of 52.5 µg/m3, with increasingly stronger effects at higher PM2.5 concentrations).