Age at menarche and its influencing factors in North Korean female refugees.

BACKGROUND Age at menarche is known to be regulated by genetic and environmental factors. To date, no menarcheal data are available on North Korean women. In this cross-sectional survey, we investigated age at menarche and its possible influencing factors in North Korean refugees. METHODS Four hundred and eleven North Korean refugees were surveyed at a North Korean female refugee camp using a structured questionnaire within 3 months of immigration. Menarcheal age was requested and the data obtained were analysed with respect to age at interview, region of residence in North Korea, education, food preference and sleep duration. RESULTS Mean age at menarche was 16.0+/-2.1 years (mean+/-SD). Univariate analysis demonstrated a significant difference in the menarcheal age among the different food preference groups (P=0.0236). Sleep duration was found to be significantly and negatively correlated with age at menarche (R=-0.23, P<0.0001). However, generalized linear model (GLM) analysis revealed that region of residence at menarche (P=0.0209) and sleep duration (P=0.0007) were significant determinants. Food preference played a role as an effect modifier in the relationship between the region of residence at menarche and age at menarche. CONCLUSION Age at menarche seemed to be delayed in North Korean refugees. GLM analysis showed that sleep duration and region of residence at menarche were significant influencing factors of age at menarche in this study population.