Genetics help determine age at menarche

Genetic effects explain about half the variation in age at menarche, and nonshared environmental factors account for the rest, according to a study of related pairs of women with different combinations of shared genetic, environmental, and childhood factors.

British researchers examined familial concordance for age at menarche in 25,970 women who had at least 1 first- or second-degree relative also enrolled in the study. Participants included mother-daughter pairs, monozygotic twins, dizygotic twins, half-sisters, grandmother-granddaughter pairs, and aunt-niece pairs.

Heritability accounted for an estimated 57% of the variation in age at menarche in the study population. A woman's age at menarche was strongly related to that of her first-degree relatives. Associations for second-degree relatives were weaker.

Morris DH, Jones ME, Minouk MJ, Ashworth A, Swerdlow AJ. Familial concordance for age at menarche: analyses from the Breakthrough Generations Study. Paediatr Perinat Epidemiol. 2011;25(3):306-311.