Linear and ponderal growth changes in boys and girls from Puerto Madryn (Patagonia, Argentina) between 2001 and 2016

Background: The phenotypic plasticity in growth pattern that takes place over time is described as “secular trend”. The presence of secular changes evidences shifts in the environmental conditions under which a population lives. In this regard, the study of the population residing in the northeast of Argentine Patagonia is interesting because it underwent a rapid demographic growth and urban sprawl in the last 50 years. 
Objective: To compare height and body weight of two groups of boys and girls between 6 and 14 years old from Puerto Madryn (northeast of Argentine Patagonia) and estimate secular trend changes during the first decades of 21st century. 
Sample and Methods: Height and body weight of two groups of schoolchildren were compared. Data of the first group (G1) was collected in the 2001–2006 period, and of the second (G2) during 2014–2016. 
To analyze the comparison between groups, the Friedman and Wilcoxon test (p < 0.05) were used. Centile values (3rd, 50th and 97th) of the variables by sex and age in both groups were also calculated. Then, they were compared using the Wilcoxon test. 
Results: Both sexes showed statistically significant differences for height in all centiles and for body weight in the 50th and 97th centiles. G2 values were above G1 for most ages. 
Conclusion: Boys and girls from Puerto Madryn show a positive secular trend in linear and ponderal growth patterns. These changes, registered during the first decades of the 21st century, are possibly related to the urban sprawl of the city and the variations in the associated socio-environmental and demographic conditions.