Evaluating preschool linear growth velocities: an interim reference illustrated in Nepal

Abstract

Objective: An annualised linear growth velocity (LGV) reference can identify groups of children at risk of growing poorly. As a single velocity reference for all preschool ages does not exist, we present an interim tool, derived from published, normative growth studies, for detecting growth faltering, illustrating its use in Nepali preschoolers.

Design: The WHO Child Growth Velocity Standard was adapted to derive 12-month increments and conjoined to the Tanner-Whitehouse Height Velocity Reference data yielding contiguous preschool linear growth annualised velocities. Linear restricted cubic spline regressions were fit to generate sex-specific median and standard normal deviate velocities for ages 0 through 59 months. LGV Z-scores (LGVZ) were constructed, and growth faltering was defined as LGVZ < –2.

Setting: Use of the reference was illustrated with data from Nepal’s Tarai region.

Participants: Children contributing the existing growth references and a cohort of 4276 Nepali children assessed from 2013 to 2016.

Results: Fitted, smoothed LGV reference curves displayed monotonically decreasing 12-month LGV, exemplified by male/female annual medians of 26·4/25·3, 12·1/12·7, 9·1/9·4, 7·7/7·8 and 7/7 cm/years, starting at 0, 12, 24, 36 and 48 months, respectively. Applying the referent, 31·1 %, 28·6 % and 29·3 % of Nepali children <6, 6–11 and 12–23 months of age, and ∼6 % of children 24–59 months, exhibited growth faltering. Under 24 months, faltering velocities were more prevalent in girls (34·4 %) than boys (25·3 %) (P < 0·05) but comparable (∼6 %) in older preschoolers.

Conclusions: A LGV reference, concatenated from extant data, can identify preschool groups at-risk of growth faltering. Application and limitations are discussed.

Keywords: Anthropometry; Growth faltering; Growth velocity reference; Linear growth velocity; Nepal.

Graphical abstract

Fig. 1

WHO-Tanner growth velocity reference curve: plotted medians and modelled 12- month velocities by sex from birth (month 0) through 59 months of age*^†. *Age at the start of interval. ^†Generated using a cubic-restricted spline model with knots at 2, 6, 12, 27 and 50 (dotted lines) months of age:

Fig. 2

WHO-Tanner modelled linear growth velocity reference curve for boys from birth (month 0) through 59 months of age at the start of the growth interval (median + 2 Z-scores)

Fig. 3

WHO-Tanner modelled linear growth velocity reference curve for girls from birth (month 0) through 59 months of age at the start of the growth interval (median + 2 Z-scores)

Fig. 4

Annualised linear growth velocities of Nepali boys aged 0–59 months at the start of the growth interval, in the Tarai measured between 2013 and 2016, plotted against the WHO-Tanner modelled linear growth velocity reference curve (median + 2 Z-score)

Fig. 5

Annualised linear growth velocities of Nepali girls aged 0–59 months at the start of the growth interval, in the Tarai measured between 2013 and 2016, plotted against the WHO-Tanner modelled linear growth velocity reference curve (median + 2 Z-score)