Association of Height, BMI, and AD in Young Children May Be Transient

The association of atopic dermatitis (AD) with short stature and increased body mass index (BMI) in early childhood may be transient, often resolving by mid-adolescence, according to a large cohort study published online November 17 in JAMA Dermatology.

“The potential for ‘catch up’ in height for children with atopic dermatitis observed in our study may be explained with resolution of atopic dermatitis or successful treatment,” write senior author Aaron M. Drucker, MD, ScM, from the Division of Dermatology, University of Toronto, and Women’s College Hospital in Toronto, Canada, and colleagues. They postulated that while the association between AD and shorter height is “is likely multifactorial,” it may be driven in part by sleep loss caused by AD, or corticosteroid treatment of AD, both of which can result in growth retardation and subsequent increased BMI.

The researchers used data from TARGet Kids!, a prospective, longitudinal cohort study designed to study multiple health conditions in children from general pediatric and family practices across Toronto. Their study included 10,611 children for whom there was data on height, weight, BMI, and standardized z scores, which account for age and sex differences in anthropometric characteristics. Clinically relevant covariates that were collected included child age, sex, birth weight, history of asthma, family income, maternal and paternal ethnicity, and maternal height and BMI.

The mean age of the children in the study at cohort entry was 23 months and they were followed for a median of 28.5 months, during which time they had a median of two visits. At baseline, 947 (8.9%) children had parent-reported AD, with this number rising to 1834 (17.3%) during follow-up.

After adjusting for covariates, AD was associated with lower mean z-height (P < .001), higher mean z-BMI (P = .008), but lower mean z-weight (P < .001) compared with children without AD. Using World Health Organization growth tables, the researchers estimated that “children with atopic dermatitis were, on average, approximately 0.5 cm shorter at age 2 years and 0.6 cm shorter at age 5 years than children without atopic dermatitis” after adjusting for covariates. They also estimated that children with AD were “on average, approximately 0.2 more BMI units at age 2 years” than children without AD. The associations between AD and height diminished by age 14 years, as did the association between AD and BMI by age 5½ years.

“Given that we found children with atopic dermatitis to be somewhat less heavy, as measured by z-weight, than children without atopic dermatitis and that this association did not attenuate with age, it is possible that our findings for BMI, and perhaps those of previous studies, are explained mainly by differences in height,” the authors write. “This distinction has obvious clinical importance — rather than a focus on obesity and obesogenic behaviors being problematic in children with atopic dermatitis, research might be better directed at understanding the association between atopic dermatitis and initially shorter stature.”

Asked to comment on the study results, Jonathan Silverberg, MD, PhD, MPH, associate professor of dermatology, George Washington University School of Medicine and Health Sciences, Washington, DC, told Medscape Medical News he would have preferred using the wording “in addition to focusing on obesity,” rather than “focus on obesity.”

“We should not ignore diet and sedentary activity as important factors,” he said, pointing to another recent study that found higher rates of eating disorders associated with AD.

Silverberg said that he was not familiar enough with the cohort sample to comment on how representative it is of the Canadian population, or on how generalizable the results are to other regions and populations. Generalizability, he added, “is an important issue, as we previously found regional differences with respect to the association between AD and obesity.”

In addition, he noted that in the study, AD was defined as an “ever history” of disease rather than “in the past year or currently,” so even though it is a longitudinal study, “it is really looking at how AD at any point in patients’ lives is related to weight or stature,” he explained. But, he added, “many cases of childhood AD ‘burn out’ or become milder/clear as the children get older. So, if the AD clears, then one would expect to see attenuation of associations as the children get older. However, this doesn’t tell us about how persistent AD into later childhood or adolescence is related to height or weight.”

Previous studies found that short stature and obesity were particularly associated with moderate — and even more so severe — atopic dermatitis, Silverberg said. It is likely that most patients in this primary care cohort had mild disease, he noted, so the effect sizes are likely diluted by mostly mild disease “and not relevant to the more persistent and severe AD patients encountered in the dermatology practice setting.” 

JAMA Dermatol. Published online November 17, 2021. Abstract

The study was supported by the Department of Medicine, Women’s College Hospital, and the Canadian Institutes of Health Research.

One author reported receiving compensation from the British Journal of Dermatology (reviewer and Section Editor), the American Academy of Dermatology (guidelines writer), and the National Eczema Association (grant reviewer) and has served as a paid consultant for the Canadian Agency for Drugs and Technologies in Health outside the submitted work. No other disclosures were reported. Silverberg has disclosed no relevant financial relationships.

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.

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