Influence of socioeconomic factors on age at menarche of Polish girls.

The aim of the study is to determine the influence of socioeconomic factors on age at menarche in Polish girls. Questionnaire data of 2016 girls were collected during the cross-sectional research. Within the socioeconomic variables parents' education, urbanization, number of children in the family and date of menarche were considered. To examine the effects of the analyzed socioeconomic factors on age at menarche, the analysis of variance and the Kaplan-Meier method were used. To estimate the mutual relations between the analyzed variables, the method of classification and regression trees (CART) was applied. The socioeconomic factors significantly affect age at menarche. The latest crossed threshold of puberty is observed in girls whose parents inhabit rural areas. Family size also affects age at menarche: girls from large families are the latest who have crossed the pubertal threshold. The method of classification and regression trees indicates that the most important predictive factor is the number of children in the family. The obtained results confirmed the complex effect of the analyzed variables. A factor that conditions occurrence of menarche most of all is the number of children in the family and then the urbanization degree of mother's place of residence. Further research is clearly required--especially research including analyses of mutual relations between variables and their complex effect.