Familial resemblance for the age at menarche in Basque population

A cross-sectional sample from Biscay province (Basque Country, Spain) compo sed of 296 subjects from 143 nuclear families was analysed. The aim of this research was to study familial resemblance for the age at menarche and to investigate the influence that BMI, fatness and several socio-familial vari ables have on the menarcheal age. The influence of these variables on the d egree of similarity of mother-daughter and sister-sister pairs for the age at onset of menstruation will be determined. Mean ages at menarche of mothe rs estimated by retrospective methodology (12.88 years, SD = 1.57) and daug hters assessed by probit analysis (12.34 years, SD = 1.00) showed no statis tically significant differences. Mother-daughter and sister-sister correlat ions increased after controlling for BMI, fatness and several socio-familia l variables (0.25 vs 0.36 and 0.28 vs 0.44, respectively). The results reve aled the importance of BMI, fatness, socio-economic level and the number of people living together in the household on menarcheal age and on the estim ation of correlations. However, no influence from sibship size (possibly be cause this variable is a part of the people living together in the househol d) nor from birth order of the subjects was observed.