The Changing Social Gradient in Age at Menarche across Cohorts and Generations in Norway

Martin Flatø , Norwegian Institute of Public Health
D. Susie Lee, Max Planck Institute for Demographic Research (MPIDR)

Age at menarche (AAM; the first occurrence of menstruation) is a critical milestone for women’s fertility and health trajectory. While children growing up in wealthier families used to experience menarche relatively early, the pattern now appears to have reversed in some western societies. We use a unique compilation of cohort surveys linked across generations with individual register data in Norway, to track the secular trend of AAM and social gradient therein. From the sample of 99,921 women, we find that AAM has declined by approximately 5 months across cohorts born 1960-2007 and that a social gradient emerged from 1980s. In a balanced sample of 9,345 mother-daughter pairs, we find a three month difference between the highest and lowest income quintile in the daughter generation born 2002-2007, but no social gradient among their mothers born 1960-1990. Using a first difference regression, we find a stronger decline in AAM in daughters compared to their mothers if the mother grew up in household with lower socioeconomic position (0.19 years difference between the top and bottom percentile; CI: 0.06-0.31), and also if the daughter’s socioeconomic position is worsened compared to that of the mother during her own childhood (0.16 years if the position drops from the top to the bottom percentile; CI: 0.06-0.26). Using relative income or relative education as indicator of socioeconomic position yielded similar results. We conclude that the earlier AAM in low socioeconomic groups is a novel trend that requires more understanding of underlying mechanisms.

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 Presented in Session 49. Social Inequalities in Sexual and Reproductive Health