Vision of Research on Human Linear Growth

Abstract

The human body grows in length from conception to the maximal adult height over two decades. The shortest male population averages ∼150 cm and the tallest ∼183 cm. Nonetheless the dimensions of head and trunk are highly comparable, with the vast difference in the leg length. Stunting is a personal condition in which an individual has a standing height-for-age (HAZ) of less than two standard deviations of the standard curve median. It is associated with increased mortality, morbidity, and functional deficits. The process of losing relative stature is known as linear growth retardation, first attributed to chronic protein deficiency, then to an assortment of micronutrient deficiencies, and most recently to inflammation from unhygienic environmental conditions. Public health intervention trials responding to each of these possibilities have failed to produce true reversal responses measured in the 10s of centimeters. As to biological insights, there is no convenient way to separate weight from length growth with sonographic monitoring, but a third of infants can be born stunted. Normative growth (standard curves) competes with epigenetic adaptation (programming) as the beacon for in utero growth. Major investments into field trials allow us to discard multiple micronutrients and water/sanitation/hygiene interventions as measures to reverse established stunting. The preponderance of evidence is against catch-up growth during puberty. Future publications will be in the conceptual domain, resolving metrics, while the full range of stimuli and exposures impeding growth will be elucidated. Advances in measurement techniques in anthropometry and immunology and endocrinology will be mobilized to the literature.