Postmenarche growth: cohort study among indigenous and non-indigenous Chilean adolescents

BACKGROUND In Chile, indigenous and non-indigenous schoolchildren have the same stature when they begin school but indigenous adults are shorter, indicating the importance of analyzing growth during puberty. The aim of this study was to compare the growth of indigenous and non-indigenous girls during the 36 months after menarche in Chile's Araucanía Region. METHODS A concurrent cohort study was conducted to compare growth in the two ethnic groups, which were comprised of 114 indigenous and 126 non-indigenous girls who recently experienced menarche and were randomly selected. Height was measured at menarche and at 6, 12, 18, 24 and 36 months post-menarche. General linear models were used to analyze growth and a generalized estimating equation model was used to compare height at 36 months post-menarche. RESULTS At menarche, the Z-score of height/age was less for indigenous than non-indigenous girls (-0.01 vs. -0.61, p < 0.001). Indigenous girls grew at a slower rate than non-indigenous girls (6.5 vs. 7.2 cm, p = 0.02), and height at 36-months post-menarche reached -0.82 vs. -0.35 cm (p <0.001). In an adjusted model at 36 months post-menarche, indigenous girls were 1.6 cm shorter than non-indigenous girls (95% confidence interval: -3.13 to -0.04). CONCLUSIONS The height of indigenous girls at menarche was lower than that of non-indigenous girls and they subsequently grew less, maintaining the gap between the two groups. At the end of the follow-up period, the indigenous girls were shorter than their non-indigenous peers.