Rural infants show greater skin barrier impairment at birth than urban infants

Infants living in urban areas had lower transepidermal water loss values than infants in rural areas, according to a letter published in Pediatric Allergy and Asthma.

This association occurred despite the fact that urban environments are typically associated with skin barrier damage and higher transepidermal water loss (TEWL), which, in turn, is associated with increased risk for atopic conditions, Michael Brandwein, PhD, cofounder and vice president of research and development, MYOR Diagnostics Ltd., and colleagues wrote.

The researchers evaluated data of 242 near-term or full-term infants between 1 and 5 days after birth who were enrolled in the Comprehending Atopic Risk Elements (CARE) multicenter, prospective observational longitudinal study between June 2020 and April 2022.

The cohort included 140 infants from rural areas and 102 infants from urban areas. Clinicians measured each infant’s and parent’s forearm and forehead TEWL values at rest three times.

Data collection revealed that a greater proportion of fathers of rural infants than urban infants smoked during pregnancy (46% vs. 29.7%; P = .015), whereas fewer rural fathers had dogs at home (15.6% vs. 27.5%; P = .039).

Most infants were bathed within 6 hours after birth, including 79.3% of the rural infants and 82.4% of the urban infants (P = .013). However, 5.7% of the rural infants and 11.8% of the urban infants were not bathed for more than 48 hours after birth.

Rural infants had significantly higher median TEWL measurements for the forearm (16.6 g/m² per hour vs. 11.75 g/m² per hour; P = .001) and forehead (10.9 g/m² per hour vs. 7.8 g/m² per hour; P < .001) than urban infants. Researchers noted these trends were consistent among their parents.

A multivariate logistic regression model showed that urban infants were much less likely to have above-median birth TEWL measurements for their forearm and forehead (OR = 0.22; 95% CI, 0.09-0.48).

Although there were no significant differences in demographics or familial history of atopic conditions between the urban and rural infants, the researchers noted that these differences in TEWL measurements between the groups were significant.

Also, the researchers acknowledged that their findings contradict earlier studies attributing skin barrier damage to urban environments, considering the higher TEWL values found among the rural participants in this study.

The researchers said these findings were noteworthy because infants who developed atopic dermatitis had higher TEWL values and the risks that urban lifestyles present for atopic conditions are well known.

Therefore, the researchers wrote, high TEWL values at birth do not necessarily mean the infant has a higher risk for AD or other atopic conditions, although further studies examining these relationships are warranted.

The researchers plan to finish gathering data about atopic outcomes in this cohort this spring and report on the development of AD and food allergies in association with TEWL values and rural and urban residencies.