AimInfections can impair cognitive development, but their role on adverse childhood educational outcomes is unknown. We examined the associations of infectious morbidity and inflammatory biomarkers with grade repetition and school absenteeism.MethodsWe followed 2762 Colombian children aged 5-12 years for a school year. We quantified inflammatory biomarkers at enrolment and prospectively recorded incidence of gastrointestinal and respiratory infections, doctor visits and absent days from school using pictorial diaries. We estimated adjusted relative risks (ARR) with 95% confidence intervals (CI) for grade repetition and absenteeism by infectious morbidity burden and inflammatory biomarker categories, and percentages of the associations mediated through absenteeism.ResultsMorbidity was associated with increased risk of grade repetition. ARR (95% CI) of grade repetition comparing high versus no incidence of gastrointestinal, respiratory and ear infections were, respectively, 2.17 (1.00, 4.72), 2.31 (1.28, 4.16) and 2.57 (1.13, 5.86). Infections also predicted school absenteeism, which mediated 35%, 31% and 38% of the corresponding morbidity-grade repetition associations. Elevated white blood cells (WBC), especially granulocytes, were related to increased grade repetition and school absenteeism risks.ConclusionChildhood infections and elevated WBC are associated with grade repetition and school absenteeism. Absenteeism does not fully explain the morbidity-grade repetition associations.

Puberty affects sleep phasing. However, it is unclear if sleep duration earlier in childhood could influence the timing of pubertal events. We aimed to assess the association between middle childhood nighttime sleep duration and age at menarche (AAM).

We examined the associations of middle childhood infectious morbidity and inflammatory biomarkers with adolescent internalizing and externalizing behavior problems. We recruited 1018 Colombian schoolchildren aged 5-12 years into a cohort. We quantified white blood cell (WBC) counts and C-reactive protein at enrollment and prospectively recorded incidence of gastrointestinal, respiratory, and fever-associated morbidity during the first follow-up year. After a median 6 years, we assessed adolescent internalizing and externalizing behavior problems using child behavior checklist (CBCL) and youth self-report (YSR) questionnaires. Behavior problem scores were compared over biomarker and morbidity categories using mean differences and 95% confidence intervals (CI) from multivariable linear regression. Compared with children without symptoms, CBCL internalizing problem scores were an adjusted 2.5 (95% CI: 0.1, 4.9; p = .04) and 3.1 (95% CI: 1.1, 5.2; p = .003) units higher among children with moderate diarrhea with vomiting and high cough with fever rates, respectively. High cough with fever and high fever rates were associated with increased CBCL somatic complaints and anxious/depressed scores, respectively. WBC >10,000/mm(3) was associated with both internalizing problem and YSR withdrawn/depressed scores. There were no associations with externalizing behavior problems. Whether or not decreasing the burden of common infections results in improved neurobehavioral outcomes warrants further investigation.

A low second-to-fourth digit ratio (2D:4D) is a purported biomarker of increased intrauterine androgenic exposure, presumably linked to postnatal behavior. We aimed to examine the associations between 2D:4D and adolescence behavior problems expected from high (externalizing and attention problems) or low (internalizing problems) prenatal androgen exposure. We conducted a cross-sectional study of 1042 Colombian schoolchildren aged 11-18 y. We examined whether caliper-assessed 2D:4D was associated with behavior problems per the Youth Self-Report questionnaire. Mean problem standardized score point differences were estimated between hand- and sex-specific quintiles of 2D:4D with use of multivariable linear regression. Lower right-hand 2D:4D was associated with decreased externalizing and internalizing behavior problem scores. Corresponding lowest-to-median quintile adjusted mean differences (95% CI) were -4.6 (-7.5, -1.7) and -3.5 (-6.4, -0.6) points in boys; and -3.4 (-5.9, -0.9) and -3.5 (-6.2, -0.8) points in girls. Lower right-hand 2D:4D was also related to less attention and thought problems in boys, and to less social problems among girls. Associations were nonlinear, apparent only below 2D:4D medians, and stronger with the right than the left hand. In conclusion, right-hand 2D:4D is related to behavior problems in adolescence in directions that are not fully consistent with an androgenic exposure origin.

We examined the associations of chronotype with behavior problems in a cross-sectional study of 957 Colombian adolescents (mean age, 14.6 years; 56% female), in addition to the mediating role of social jetlag. The midpoint of bedtime and waketime on free days, corrected for sleep debt accumulated during school week (MSFsc), was estimated from parent reports and used to assess chronotype. Behavior problems were evaluated through the Youth Self-Report (YSR) and the parent-completed Child Behavior Checklist (CBCL) questionnaires. We estimated adjusted mean differences with 95% CI in externalizing, internalizing, attention, social, and thought problem scores per one hour difference in chronotype using linear regression. Later chronotype was related to internalizing and externalizing behavior problems. Eveningness was associated with higher adjusted mean YSR scores (unit difference per hour) in externalizing behavior (1.0; 95% CI: 0.6, 1.5), internalizing behavior (0.6; 95% CI: 0.2, 1.1), attention problems (0.2; 95% CI: 0.0, 0.3), social problems (0.4; 95% CI: 0.1, 0.8), and thought problems (0.3; 95% CI: 0.1, 0.6). Similar patterns were observed with the CBCL. The associations of chronotype with somatic complaints and social problems were stronger in boys than they were in girls. Later chronotype was related to social jetlag but social jetlag was only associated with somatic complaints and attention problems, and mediated 16% and 26% of their corresponding associations with chronotype. In conclusion, later chronotype is associated with behavior problems in adolescence. Social jetlag does not substantially mediate these associations.

OBJECTIVE:Telomere length (TL) attrition is related to chronic disease risk. However, less is known on whether TL predicts infectious outcomes, especially in childhood. We examined whether leukocyte TL (LTL) was associated with subsequent infectious morbidity in schoolchildren. METHODS:We assessed LTL in 717 Colombian children 5-12 years-old at the beginning of a school year and followed them through the year for daily occurrence of common infection symptoms and doctor visits. We estimated adjusted incidence rate ratios (IRR) with 95% confidence intervals (CI) of gastrointestinal and respiratory syndromes for quartiles of standardized LTL Z score and per unit LTL Z score. RESULTS:A longer LTL was associated with increased incidence of all infectious morbidity syndromes considered. Adjusted IRR (95% CI) per unit LTL Z score were 1.55 (1.20, 2.00) for diarrhea with vomiting, 1.34 (1.13, 1.60) for cough with fever, 1.70 (1.28, 2.28) for ear infection, and 1.66 (1.36, 2.02) for doctor visits with symptoms. CONCLUSIONS:Longer LTL is related to increased incidence of common infectious morbidities in middle childhood.

Background: The efficacy of cholecalciferol (vitamin D3) food fortification in low-and middle-income countries near the Equator is unknown.Objectives: We examined the effects of providing cholecalciferol-fortified skim milk to adolescents and their mothers on serum total 25(OH)D, free 25(OH)D, and vitamin D-binding protein (DBP) concentrations in a randomized controlled trial.Methods: We randomly assigned 80 Colombian families each with a child aged 12-14.5 y and their mother 1 L of skim milk daily, either fortified with 2400 IU (60 mu g) cholecalciferol or unfortified, for 6 wk. We prescribed 500 mL of milk daily to adolescents; mothers consumed the remainder ad libitum. We estimated intent-to-treat effects as the between-arm difference in the change in serum total and free 25(OH)D and DBP concentrations from baseline to the end of follow-up. Secondary analyses included stratification by baseline characteristics and per -protocol comparisons.Results: Among adolescents, fortification effects (95% CI) on serum total 25(OH)D, free 25(OH)D, and DBP concentrations were 5.4 nmol/L (2.1, 8.8 nmol/L), 0.6 pmol/L (-0.2, 1.4 pmol/L), and -416 nmol/L (-944, 112 nmol/L), respectively. Effects on total 25(OH)D were stronger in adolescents with lower DBP concentrations, darker skin, less sunlight exposure, and higher compliance than in their respective counterparts. Fortification increased free 25(OH)D concentrations in high compliers. Among mothers, the effects (95% CI) on total 25(OH)D and DBP concentrations were 4.0 nmol/L (0.6, 7.5 nmol/L) and -128 nmol/L (-637, 381 nmol/L), respectively. There were no adverse events.Conclusions: Provision of cholecalciferol-fortified skim milk increases serum total 25(OH)D concentrations in Colombian adolescents and adult women.

Short telomere length is associated with chronic diseases and decreased lifespan. Vitamin D and its binding protein (DBP) may maintain telomeres through anti-inflammatory actions, yet the role of vitamin D on telomere length is uncertain, especially in children. We assessed the cross-sectional associations of plasma 25-hydroxy vitamin D (25(OH)D) and DBP with leukocyte telomere length (LTL) in a group of 447 children ages 5–12 years from the Bogotá School Children Cohort. We compared the distribution of age-standardized LTL (z-score) between 25(OH)D categories and between DBP quartiles overall and by sex. Overall, 25(OH)D was not significantly associated with LTL. Nonetheless, among boys, 25(OH)D < 50 nmol/L was related to an adjusted 0.36 shorter LTL z-score (95% CI: −0.71, −0.01; P = 0.046) compared with 25(OH)D ≥ 75 nmol/L. There was no association among girls. DBP was not significantly related to LTL. Intervention studies are warranted to determine whether increasing vitamin D status enhances telomere length.

We examined the associations of middle childhood and adolescence nighttime sleep duration with adolescence internalizing and externalizing behavior problems per the Youth Self-Report (YSR) and the Child Behavior Checklist (CBCL) questionnaires, in a cohort of 889 Colombian schoolchildren. We estimated adjusted differences with 95% confidence intervals (CI) in mean behavior problem t-scores in standardized units between recommended sleep duration categories and as a continuous exposure using multiple linear regression and restricted cubic spline models, respectively. Compared with sleep duration within recommendations, middle childhood sleep above recommendations was related to 4.6 (95% CI: 1.6, 7.6; p = .004) and 5.4 (95% CI: 1.2, 9.7; p = .01) adjusted units higher YSR and CBCL externalizing problem scores, respectively. In continuous exposure analyses, this association seemed restricted to children aged ≥11 years. Longer sleep, both in categories and as a continuous exposure, was also associated with increased CBCL internalizing problems. Results did not differ by sex or weekend/weekday sleep. Sleeping under recommendations in middle childhood was not significantly related to behavior problems; nevertheless, shorter sleep in adolescence, in both categorical and continuous scales, was significantly related to behavior problems. In conclusion, behavior problems in adolescence are associated with longer sleep in middle childhood and shorter sleep in adolescence.

Introduction: Half of the Colombian households experience some degree of food insecurity. Food insecurity has been associated with malnutrition, which could result in micronutrient deficiencies in children; however, the evidence is not conclusive. Objective: To examine the associations between food insecurity and blood concentrations of hemoglobin, ferritin, vitamin A, vitamin B12, folate, and zinc in school-age children from Bogota, Colombia. Materials and methods: We conducted a cross-sectional study among 2,660 children aged 5-12 from Bogota's public schools. We assessed their household food insecurity level with the Spanish version of the Household Food Security Survey Module (HFSSM), a validated scale, and quantified blood biomarkers of iron, vitamin A, folate, vitamin B12, and zinc status. We examined the associations between food insecurity, severe hunger, and micronutrient status biomarkers using propensity scores. Results: Three-quarters of households had some degree of food insecurity and 12 % had food insecurity and severe hunger. Prevalence of marginal vitamin B12 status and vitamin A and zinc deficiencies were, respectively, 17%, 14%, and 1.4%. Compared with children from households without severe hunger, those exposed to it had lower adjusted mean concentrations of vitamin A, vitamin B12, and folate, but these differences were not statistically significant. Conclusion: Food insecurity with severe hunger was not associated with micronutrient status biomarkers in Colombian school-age children. The HFSSM may adequately measure hardship in food acquisition due to lack of resources, but it does not yield an index that is associated with micronutrient status biomarkers.

Introducción. La mitad de los hogares colombianos padecen inseguridad alimentaria. Esta se ha asociado con malnutrición, la que, según algunos estudios, podría reflejarse en un déficit de micronutrientes en los niños, aunque los datos no son concluyentes. Objetivo. Establecer la asociación entre la inseguridad alimentaria y los niveles de hemoglobina, hierro, vitamina A, vitamina B12, folato y cinc, en escolares de Bogotá. Materiales y métodos. Se hizo un estudio de corte transversal. Se aplicó la escala del Household Food Security Survey Module (HFSSM) validada en español en una muestra de hogares de escolares de Bogotá, para establecer la prevalencia de inseguridad alimentaria. Utilizando el índice de propensión, se exploró la asociación entre la inseguridad alimentaria, el hambre grave y las concentraciones de hierro, vitamina A, folato, vitamina B12 y cinc, estimadas en muestras de suero provenientes de los escolares. Resultados. Se incluyeron 2.660 escolares. En el 76 % de los hogares había inseguridad alimentaria, de los cuales el 11,6 % se clasificaba como inseguridad alimentaria con hambre grave. La deficiencia marginal de vitamina B12 fue del 17 % y las de vitamina A y cinc, de 14 y 1,4 %, respectivamente. Aunque se encontraron niveles promedios más bajos de vitamina A (-0,009 μmol/L; IC95% -0,13 - 0,03 μmol/L), vitamina B12 (-19,57 pmol/L; IC95% -72,55 - 29,94 pmol/L) y folato (-9,25 nmol/L; IC95% -29,55 - 18,66 nmol/L) en los niños expuestos a inseguridad alimentaria con hambre grave, al compararlos con los de los no expuestos, las diferencias no fueron estadísticamente significativas. Conclusiones. La inseguridad alimentaria con hambre grave no se asoció los valores de micronutrientes o sus deficiencias en los escolares. La escala del HFSSM mide adecuadamente la dificultad en la adquisición de alimentos por falta de recursos, pero no permite establecer una asociación con las concentraciones de micronutrientes.

Leukocyte telomere length (LTL) is associated with obesity and may be involved in its aetiology, but few studies have focused on children and most have been cross-sectional. We assessed the relation of LTL with adiposity development in a prospective study of Colombian children. We quantified LTL at enrollment in 722 children aged 5-12 years and measured anthropometry annually for a median 6 years. Using mixed effects models, we estimated changes in adiposity measures including BMI and waist circumference (WC)-for-age z-scores in relation to baseline LTL z-score. In girls, longer LTL was linearly related to a lower increase in WC z-score from age 6 to 16 years. Every 1 SD LTL was associated with an adjusted 0.13 units lower increase in WC (95% CI: -0.23, -0.03; p = 0.01). In conclusion, longer LTL among girls in middle childhood is associated with smaller increases in WC, an indicator of abdominal adiposity.

Background/objectives Adherence to a “Western” style dietary pattern has been related to behavior problems in children in high-income countries; however, dietary patterns may differ in countries undergoing the nutrition transition. Associations of dietary patterns with behavior problems in a Latin American context have not been evaluated. Subjects/Methods Mothers of 385 children 5 to 12 y old completed a food frequency questionnaire (FFQ) on the children’s usual intake at enrollment into a cohort study. Four dietary patterns were identified through principal component analysis of the FFQ: animal protein, snacking, cheaper protein, and traditional/starch. After a median 6 y follow-up, adolescents reported behavior problems via the Youth Self Report, a standardized questionnaire. We compared the continuous distributions of externalizing and internalizing behavior problems and their subscales across quartiles of adherence to the four dietary patterns using multivariable linear regression. Results Boys in the highest quartile of adherence to the animal protein pattern in middle childhood had an adjusted 5.5 units lower (95% CI −9.5, −1.5) mean total externalizing problems score compared with boys in the lowest quartile ( P trend = 0.008). Adherence to the animal protein pattern was also inversely related to the aggressive behavior externalizing subscale in a dose–response manner among boys ( P trend = 0.009). There were no associations between adherence to other dietary patterns and externalizing problems in boys or girls. There were no associations with internalizing problems. Conclusion Adherence to an animal protein dietary pattern in middle childhood was associated with less externalizing behavior problems in adolescent boys.

BACKGROUND Vitamin D deficiency (VDD) is associated with depression and schizophrenia in adults. The effect of VDD in childhood on behavioral development is unknown. OBJECTIVES We aimed to study the associations of VDD and vitamin D binding protein (DBP) in middle childhood with behavior problems in adolescence. METHODS We quantified plasma total 25-hydroxyvitamin D [25(OH)D] and DBP in 273 schoolchildren aged 5-12 y at recruitment into a cohort study in Bogota, Colombia. Externalizing and internalizing behavior problems were assessed after a median 6-y follow-up by parental report [Child Behavior Checklist (CBCL)] and self-report [Youth Self-Report (YSR)]. We estimated mean problem score differences with 95% CIs between exposure categories using multivariable linear regression. We also compared the prevalence of clinical behavior problems (score >63) between exposure groups. We assessed whether the associations between DBP and behavior problems were mediated through VDD. RESULTS Mean ± SD CBCL and YSR externalizing problems scores were 56.5 ± 9.3 and 53.2 ± 9.5, respectively. Internalizing problems scores averaged 57.1 ± 9.8 and 53.7 ± 9.8, respectively. VDD [25(OH)D <50 nmol/L] prevalence was 10.3%. VDD was associated with an adjusted 6.0 (95% CI: 3.0, 9.0) and 3.4 (95% CI: 0.1, 6.6) units higher CBCL and YSR externalizing problems scores, respectively, and an adjusted 3.6 (95% CI: 0.3, 6.9) units higher CBCL internalizing problems scores. The prevalence of clinical total externalizing problems was 1.8 (95% CI: 1.1, 3.1) times higher in children with VDD than that in children without VDD. DBP concentration below the population median was related to higher YSR aggressive behavior and anxious/depressed subscale scores and to higher prevalence of clinical total externalizing problems. The associations between DBP and behavior problems were not mediated through VDD. CONCLUSIONS VDD and low DBP in middle childhood are related to behavior problems in adolescence.

Leukocyte telomere length (LTL) is a biomarker of inflammation and oxidative stress that predicts chronic disease risk. Nutritional factors are related to LTL in adulthood, but these associations are not well characterized in children. We examined whether micronutrient status biomarkers were associated with LTL in school-age children. We conducted a cross-sectional study of 330 boys and 393 girls aged 5–12 years from Bogotá, Colombia. We quantified blood concentrations of hemoglobin, ferritin, zinc, vitamin A, folate, and vitamin B-12; and measured LTL using qPCR in DNA extracted from buffy coat. We estimated mean differences in LTL by quartiles of micronutrient status biomarkers and categories of relevant sociodemographic and anthropometric covariates with the use of linear regression. In girls, plasma vitamin B-12 was positively associated with LTL (adjusted LTL difference between extreme vitamin B-12 quartiles = 0.11; P, trend = 0.02). LTL was also positively associated with birth order in girls (P, trend = 0.02). In boys, LTL was not related to the micronutrient status biomarkers but, unexpectedly, it was positively associated with birth weight (P = 0.02), height-for-age Z score (P, trend = 0.01), and serum C-reactive protein (P, trend = 0.01). LTL is associated with vitamin B-12 status among girls. LTL is also associated with birth weight, height, and C-reactive protein in boys.

We sought to determine the associations of n-3 and n-6 polyunsaturated fatty acids (PUFA) in middle childhood with externalizing and internalizing behavior problems in adolescence. Using gas-liquid chromatography, we quantified n-3 and n-6 PUFA in serum samples of 444 Colombian schoolchildren aged 5–12 years at the time of enrollment into a cohort study. After a median 6 years, adolescent externalizing and internalizing behavior problems were determined with the Youth Self Report (YSR) questionnaire. We estimated adjusted mean behavior problem score differences with 95% confidence intervals (CIs) between quartiles of each PUFA using multivariable linear regression. We also considered as exposures the Δ6-desaturase (D6D) and Δ5-desaturase (D5D) enzyme activity indices. Docosahexaenoic acid (DHA) was positively associated with externalizing problems; every standard deviation (SD) of DHA concentration was associated with an adjusted one unit higher externalizing problem score (95% CI: 0.1, 1.9). The D5D enzyme activity index was inversely related to externalizing problem scores. Alpha-linolenic acid concentration was positively associated with internalizing problem scores, whereas adrenic acid was inversely related to this outcome. Serum PUFA in middle childhood were related to behavior problems in adolescence. Some of these associations might reflect the role of D5D enzyme activity.

AbstractObjectiveTo determine if processed and ultra-processed foods consumed by children in Colombia are associated with lower-quality nutrition profiles than less processed foods.DesignWe obtained information on sociodemographic and anthropometric variables and dietary information through dietary records and 24 h recalls from a convenience sample of the Bogotá School Children Cohort. Foods were classified into three categories: (i) unprocessed and minimally processed foods, (ii) processed culinary ingredients and (iii) processed and ultra-processed foods. We also examined the combination of unprocessed foods and processed culinary ingredients.SettingRepresentative sample of children from low- to middle-income families in Bogotá, Colombia.SubjectsChildren aged 5–12 years in 2011 Bogotá School Children Cohort.ResultsWe found that processed and ultra-processed foods are of lower dietary quality in general. Nutrients that were lower in processed and ultra-processed foods following adjustment for total energy intake included: n-3 PUFA, vitamins A, B12, C and E, Ca and Zn. Nutrients that were higher in energy-adjusted processed and ultra-processed foods compared with unprocessed foods included: Na, sugar and trans-fatty acids, although we also found that some healthy nutrients, including folate and Fe, were higher in processed and ultra-processed foods compared with unprocessed and minimally processed foods.ConclusionsProcessed and ultra-processed foods generally have unhealthy nutrition profiles. Our findings suggest the categorization of foods based on processing characteristics is promising for understanding the influence of food processing on children’s dietary quality. More studies accounting for the type and degree of food processing are needed.

Circulating 25-hydroxy vitamin D (25(OH)D) is related to decreased rates of gastrointestinal and ear infections in school-age children. Vitamin D-binding protein (DBP) transports 25 (OH)D and exerts immunological functions; however, it is unknown whether DBP is associated with infectious morbidity in children. We quantified plasma DBP concentrations in 540 school-age children at the time of recruitment into a cohort study in Bogota, Colombia and obtained daily information on infectious morbidity symptoms and doctor visits during the school year. We compared the incidence rates of gastrointestinal and respiratory symptoms across quartiles of DBP concentration by estimating adjusted incidence rate ratios (IRRs) with 95% confidence interval (CI). We also estimated the per cent of the associations between DBP and morbidity that were mediated through 25(OH)D using a counterfactual frame. Mean +/- S.D. DBP concentration was 2650 +/- 1145 nmol/l. DBP was inversely associated with the rates of diarrhoea with vomiting (IRR for quartiles 2-4 vs. 1 = 0.48; 95% CI 0.25-0.92; P= 0.03) and earache/ear discharge with fever (IRR for quartiles 2-4 vs. 1= 0.29; 95% CI 0.12-0.71; P = 0.006). The DBP-morbidity associations were not mediated through 25(OH) D. We conclude that plasma DBP predicts lower incidence of gastrointestinal and ear infections in school-age children independent of 25(OH)D.

Background Iron deficiency (ID) in infancy is related to subsequent behavior problems. The effects of micronutrient status in middle childhood are uncertain. Objective The aim of the study was to examine the associations of micronutrient status biomarkers in middle childhood with externalizing and internalizing behavior problems in adolescence. Methods We assessed whether ID (ferritin <15 µg/L), anemia (hemoglobin <12.7 g/dL), or blood concentrations of zinc, vitamins A and B-12, and folate at ages 5-12 y were associated with externalizing or internalizing behavior problems in adolescence in 1042 schoolchildren from Bogotá, Colombia. Behavior problems were assessed with the Youth Self-Report questionnaire after a median 6.2 y of follow-up. Mean problem score differences with 95% CIs were estimated between categories of micronutrient status biomarkers with the use of multivariable linear regression. Results Mean ± SD externalizing and internalizing problems scores were 52.6 ± 9.6 and 53.8 ± 9.9, respectively. Among boys, middle-childhood ID, anemia, and low plasma vitamin B-12 were associated with 5.9 (95% CI: 1.0, 10.7), 6.6 (95% CI: 1.9, 11.3), and 2.7 (95% CI: 0.4, 4.9) units higher mean externalizing problems scores in adolescence, respectively-after adjustment for baseline age, time spent watching television or playing video games, mother's height, and socioeconomic status. Also in boys, ID was related to an adjusted 6.4 (95% CI: 1.2, 11.6) units higher mean internalizing problems score. There were no associations among girls. Other micronutrient status biomarkers were not associated with behavior problems. Conclusions ID, anemia, and low vitamin B-12 in middle childhood are related to behavior problems in adolescent boys. This study was registered at clinicaltrials.gov as NCT03297970.

Childhood intake of animal foods is associated with age at first menstrual period (menarche). It is unknown whether the micronutrients present in these foods could explain this association. Our objective was to investigate the associations of micronutrient status biomarkers in middle childhood with age at menarche. We quantified circulating Hb, ferritin, mean corpuscular volume, Zn, vitamin B12, erythrocyte folate and retinol in 1464 pre-menarcheal girls aged 5-12 years in Bogotá, Colombia, and followed them for a median 5·7 years for the occurrence and date of menarche. We estimated median age at menarche and hazard ratios (HR) with 95 % CI by levels of each biomarker with use of Kaplan-Meier survival probabilities and Cox regression, respectively. Median age at menarche was 12·4 years. Middle childhood Hb was inversely related to age at menarche whereas plasma ferritin was positively associated with this outcome in a linear manner. HR of menarche for every 1 sd of Hb (11 g/l) and ferritin (23·2 µg/l) were 1·11 (95 % CI 1·04, 1·18; P=0·001) and 0·94 (95 % CI 0·88, 0·99; P=0·02), respectively, after adjustment for baseline age, C-reactive protein concentration, maternal age at menarche and parity and socioeconomic status. The association with ferritin was stronger in girls aged 9-10 years at baseline. Additional adjustment for baseline height- and BMI-for-age did not change the results. We conclude that higher Fe status in middle childhood is related to later age at menarche whereas Hb concentrations are inversely associated with age at onset of menses.