Kids at Higher Altitudes Born Shorter and Have Lower Growth Trajectory

By Lisa Rapaport

September 16, 2020

(Reuters Health) - Children who live at 1,500 meters (4921.26 ft) or more above sea level are born at shorter lengths and develop on a lower growth trajectory than those born at lower altitudes, a recent study suggests.

Researchers examined data from 133 nationally-representative demographic and cross-sectional surveys administered in 59 middle- and low-income countries that included a total of 964,299 height records for children residing at altitudes ranging from 372 meters (1220.47 ft) below sea level to 5,951 meters (19524.28 ft) above sea level. Overall, 11% of the children lived at altitudes at least 1,500 meters above sea level.

Altitude was negatively associated with length-for-age/height-for-age Z scores (HAZ). And, a 1,000-meter above sea level increase in altitude was associated with a 0.163 unit decrease in HAZ after adjusting for common risk factors for reduced growth.

"Given the additional risk that residence at higher altitude poses to child growth faltering, policymakers and public health practitioners should give due attention to pregnancies and child growth at higher altitudes," said study co-author Kaleab Baye of the Center for Food Science and Nutrition at Addis Ababa University in Ethiopia.

"Specific health care guidance and monitoring are needed for the management of pregnancies and early child development at higher altitudes," Baye said by email.

The growth deficit was approximately linear through most part of the altitude distribution, researchers report in JAMA Pediatrics.

Children residing in ideal home environments grew at the same rate as the median child in the 2006 WHO growth standard up to approximately 500 meters above sea level. At higher altitudes, the average child height-for-age significantly deviated from the growth curve of the median child in the 2006 WHO reference population.

The altitude-mediated growth deficits were biologically significant and applied even for children living in ideal home environments previously shown to allow children to reach their growth potential.

One limitation of the study is the challenge of fully accounting for potential confounders such as dietary adequacy, said Emma Pomeroy, a lecturer in the department of archeology at the University of Cambridge in the UK.

The study may have also been underpowered for subgroup analysis, particularly for the subset of 1,700 kids living in ideal home environments, Pomeroy, who wasn't involved in the study, said by email.

"The results of this study matter as 15% of the global population live at altitudes above 1500m and many of these in lower- and middle-income countries, yet high altitude pregnant mothers, infants and children have often been excluded from studies aimed at defining fetal or child growth standards/reference data because of the possibility that high altitude reduced growth," Pomeroy said.

"This makes sense, but also meant there was a need to evaluate patterns of growth among children born and living at high altitude, who constitute a significant proportion of the global population, the extent to which growth limitation at high altitude results from socioeconomic factors, hypoxia, or intergenerational limitations on growth, and how children at high altitude can be helped to achieve their growth potential and avoid stunting, in line with the Sustainable Development Goals and WHO target to reduce stunting by 40% by 2025."

SOURCE: JAMA Pediatrics, online August 24, 2020.