Impact of Breastfeeding Duration on Age at Menarche

School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada.
American journal of epidemiology (Impact Factor: 5.23). 03/2011; 173(9):971-7. DOI: 10.1093/aje/kwq496
Source: PubMed


The study aims to assess the relation between breastfeeding duration and age at menarche. Analysis was based on a cohort of 994 Filipino girls born in 1983-1984 and followed up from infancy to adulthood by the Cebu Longitudinal Health and Nutrition Survey. The main outcome was self-reported age at menarche. Cox regression was used to investigate the relation between duration of exclusive and any breastfeeding with age at menarche with adjustment sequentially for specific sets of known socioeconomic, maternal, genetic, and prenatal confounders. The estimated median of age at menarche was 13.08 years. After adjustment for potential confounders of the association of breastfeeding with age at menarche, exclusive breastfeeding duration retained an independent and significant association with age at menarche. An increase in 1 month of exclusive breastfeeding decreases the hazard of attaining earlier menarche by 6% (hazard ratio = 0.94, 95% confidence interval: 0.90, 0.98). Any breastfeeding duration was not associated with age at menarche. Although this is the first longitudinal study that reveals a negative association between exclusive breastfeeding and early menarche, the relation is still elusive. Further longitudinal studies within different contexts are warranted to assess the generalizability of these findings.

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    • "The BMI and the increased rate of BMI were divided by the interquartile range, and the birth weight was categorized into interquartiles following prior research results on the relationship between birth weight and age at menarche [23]. To investigate the relationship between previous BMI before menarche and early menarche, the mother's age at menarche, birth weight, and breastfeeding, which are factors known to influence on the age of menarche, were used for a multiple logistic regression analysis [21,25,26]. The multiple logistic regression analyzed the relationship between BMI at the ages of 7, 8, and 9, and early menarche, as well as whether changes in BMI at the ages of 7 to 8, 8 to 9, and 9 to 10 before the start of menarche had any relationship with early menarche. "
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    ABSTRACT: The object of this study was to determine the relationship between body mass index (BMI) and early menarche in adolescent girls in Seoul. A retrospective study was conducted with 144 middle school students in Seoul who provided informed consent. We measured their body composition, and used the questionnaire survey method for data collection from November to December 2008. Past elemental body composition data were collected from elementary school health records of first year of middle school. The early menarcheal group was taller and heavier than the late menarcheal group (p<0.05 from 8-12 years old). The body fat percentage (%), BMI were higher in the early menarcheal girls than the late-menarcheal girls (p<0.05, age at 13). In the result of multiple logistic regression, the BMI at the age of 8 and 9 was associated with early menarche after adjusting for birth weight, breast feeding and age at menarche of the mother (BMI at the age of 8: p for trend=0.01, BMI at the age of 9: p for trend=0.04). An increase in BMI from 7 to 8 year was associated with early menarche after adjusting for birth weight, breast feeding, age at menarche of the mother (p for trend=0.048). The BMI at the age of 8 and 9 was associated with the early menarche of girls and increase in BMI from 7 to 8 year was associated with the early menarche of girls. These results suggest that BMI and increase in BMI before menarche cause early menarche. Although this study does not represent all Korean adolescent girls, it is one of the few studies that have investigated the temporal relationship between BMI and early menarche.
    Full-text · Article · Jul 2012
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    ABSTRACT: Longitudinal studies are often viewed as the “gold standard” of observational epidemiologic research. Establishing a temporal association is a necessary criterion to identify causal relations. However, when covariates in the causal system vary over time, a temporal association is not straightforward. Appropriate analytical methods may be necessary to avoid confounding and reverse causality. These issues come to light in 2 studies of breastfeeding described in the articles by Al-Sahab et al. (Am J Epidemiol. 2011;173(9):971–977) and Kramer et al. (Am J Epidemiol. 2011;173(9):978–983) in this issue of the Journal. Breastfeeding has multiple time points and is a behavior that is affected by multiple factors, many of which themselves vary over time. This creates a complex causal system that requires careful scrutiny. The methods presented here may be applicable to a wide range of studies that involve time-varying exposures and time-varying confounders.
    Full-text · Article · Mar 2011 · American journal of epidemiology
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    ABSTRACT: Early nutrition has been postulated as programming pubertal timing. Limited observational studies, mainly from Western settings, suggest puberty occurs later with breastfeeding and earlier with higher cow's milk (including infant formula) consumption. However, these observations may be socioeconomically confounded. This study examined whether breastfeeding or childhood milk consumption was associated with pubertal onset in a setting with different associations of breastfeeding and puberty with socioeconomic position. The adjusted associations of breastfeeding or milk consumption at 6 months, 3 years, and 5 years with clinically assessed age at pubertal onset (Tanner stage II) were assessed by using interval-censored regression in a population-representative Hong Kong Chinese birth cohort, "Children of 1997," with 90% follow-up (N = 7523). Compared with never breastfeeding, exclusive breastfeeding for 3+ months was unrelated to age at pubertal onset (time ratio [TR] 1.001, 95% confidence interval [CI] 0.987-1.015), as was partial breastfeeding for any length of time or exclusive breastfeeding for <3 months (TR 1.003, 95% CI 0.996-1.010), adjusted for gender, socioeconomic position, birth weight-for-gestational age, birth order, second-hand smoke exposure, and mother's age and place of birth. Daily milk consumption at 6 months (TR 1.004, 95% CI 0.991-1.018), 3 years (TR 0.995, 95% CI 0.982-1.008), or 5 years (TR 0.998, 95% CI 0.988-1.009) was also unrelated to age at pubertal onset compared with milk consumption for ≤ 1 time per week at the corresponding ages. In a non-Western setting, neither breastfeeding nor childhood milk consumption was associated with age at pubertal onset, suggesting that associations may vary by setting.
    No preview · Article · Aug 2012 · PEDIATRICS
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