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ABSTRACT
Background: Body size parameter, such as Body Mass Index (BMI), is strongly correlated with onset of menarche. Higher subcutaneous fat levels and BMI at prepubertal ages are associated with increased likelihood of early menarche.
Purpose: This study aimed to discover the BMI and its relationship to onset of age at menarche among schoolgirls of Santo Thomas 1 Medan Junior High School.
Methods: This study conducted a cross-sectional study on 100 respondents. The number of samples was taken using sample size formula for the correlation coefficient and randomly selected with cluster random sampling. Data were collected directly from respondents of this study, there were BMI measurement and interviews concerning age at menarche.
Results: Out of 100 respondents who had done physical examination and interview, only 91 respondents had complied inclusion and exclusion criteria of this study. Based on BMI category for 2-20 years of age and female gender CDC
2015, there were 49 respondents (53.8%) classified as normoweight category (5th
percentile to 85th percentile), 31 respondents (34.1%) classified as overweight category (85th percentile to 95th percentile) and 11 respondents (12.1%) classified
as obesity category (higher than 95th percentile). The mean age at menarche was
11.7 years. The lowest age at menarche was 9 years (7.7%) and the highest age at menarche was 13 years (28.6%). This study showed an association between BMI with age at menarche. The result of Chi-square test showed 0.001 as significant value (p<0.05).
Conclusion: There is an association between BMI with age at menarche. The most frequent BMI category is normoweight category and the mean age at menarche among schoolgirls of Santo Thomas 1 Medan Junior High School tends to have early menarche.
Keywords: BMI, Age at menarche, Schoolgirls.
