Correcting for artifactual correlation between misreported month of birth and attained height-for-age reduces but does not eliminate measured vulnerability to season of birth in poorer countries

Abstract

Background Height-for-age z-scores (HAZ) are associated with month of birth (MOB) in many nutrition surveys, but that link could be an artifactual result of measurement error in child birthdates. Objective We corrected estimates of the associations between HAZ and MOB for a common type of age misreporting, to measure the remaining seasonality in HAZ and identify country characteristics associated with vulnerability to seasonal changes in early life. Design We used nationally representative repeated cross-sections from all available Demographic and Health Surveys (DHS), totaling 1,363,806 children from 218 surveys in 72 countries over 1986–2016, to estimate the seasonal patterns in HAZ by MOB within each survey. Then, we corrected these estimates for each survey's random errors in recorded birth month implied by differences in attained height between children reported as born in December of one year versus January of the next. Indicators of seasonal variation between other months were modeled as functions of national-level incomes using linear regression, and visualizations were constructed using nonparametric local polynomial smoothing regressions. Results Over all surveys, misreporting MOB accounted for about one-eighth of the gap in attained height between the worst and best months to be born, which averaged 0.41 HAZ in the raw data and 0.34 HAZ after correction for age misreporting. A linear correction reduced apparent seasonality of HAZ by MOB in 49 of 72 countries, and the remaining nonartifactual differences by season of birth were larger in countries with lower average income per capita. Conclusions Measurement error in child MOB helps to explain the association between attained height and seasonal variation in early life environments, but significant seasonality in HAZ by MOB remains in many poor countries. Higher national income is associated with smoother outcomes across birth months, and birth registration efforts would improve nutrition research.

A Longitudinal Study of the Epidemiology of Seasonal Coronaviruses in an African Birth Cohort

“…However, while there was no seasonal pattern to sHCoV infection, birth in winter was significantly associated with sHCoV detection among cases and with the presence of LRTI among infants positive for sHCoV. Season of birth has previously been associated with poor birth outcomes [ 18 ] and nutritional indicators in children [ 19 , 20 ], which may be related to dietary or environmental factors [ 19 ]. Children born in autumn or winter have an increased risk of wheezing or asthma in later life, which may be partly mediated by respiratory tract infection [ 21 ].…”

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“…The specific kind of shock most often investigated is seasonal fluctuations in rainfall and temperature around the time of a child's birth, which is much more closely linked to attained height for children in poorer, more remote places than in towns and cities. Some of the apparent link between month of birth and height for age is due to random errors in recorded birth months among children without birth registrations (Larsen, Headey, and Masters 2019), but even after adjusting for those errors, there is significant variation in attained height by season of birth (Finaret and Masters 2019). Research to date has shown how sanitation, food markets, and local infrastructure can help households protect their children from seasonal climate fluctuations (Mulmi et al 2016;Shively 2017;Thapa and Shively 2018), leading to new work focusing on specific kinds of smoothing such as year-round access to a nutritious diet (Bai, Naumova, and Masters 2019).…”

Agriculture and undernutrition through the lens of economics

“…The specific kind of shock most often investigated are seasonal fluctuations in rainfall and temperature around the time of a child's birth, which is much more closely linked to attained height for children in poorer, more remote places than in towns and cities. Some of the apparent link between month of birth and height for age is due to random errors in recorded birth months among children without birth registrations (Larsen, et al, 2019), but even after adjusting for those errors there is significant variation in attained height by season of birth (Finaret and Masters, 2019). Research to date has shown how sanitation, food markets and local infrastructure can help households protect their children from seasonal climate fluctuations (Mulmi, et al, 2016, Shively, 2017, Thapa and Shively, 2018, leading to new work focusing on specific kinds of smoothing such as year-round access to a nutritious diet (Headey, et al (2017d), (bai, et al, 2019).…”