Time intervals between the age at menarche and the onset of sexual activity in Polish women born between 1959 and 2001.

Objectives: The aim of this study was to assess time intervals between the age at menarche (AM) and age at sexual initiation (ASI) in Polish women born before and after the political transformation period in Poland.
Methods: Participants were 518 women born between 1959 and 2001 in Poland. AM and ASI were based on self-report. Three birth cohorts were distinguished based on the year of birth: I (1959-1979), II (1980-1989), III (1990-2001). Three categories of AM were distinguished: early maturing (<12.0 years), average (12.0-13.0 years), and late maturing (≥14.0 years). Temporal intervals between AM and ASI were calculated.
Results: Both AM and ASI decreased in subsequent birth cohorts, with the greatest changes observed in the women born after 1989. No significant differences in the time interval between AM and ASI were observed between birth cohorts. However, the time interval between AM and ASI differed by AM category (H = 74.16; P < .001). The longest time period between AM and ASI occurred in early maturing girls (7.13 years) and the shortest in late maturing girls (3.25 years).
Conclusions: Despite the transformation and decline in both AM and ASI, the time interval between these two characteristics remained stable. Significant differences in the time interval were found among women stratified by AM. The time interval between AM and ASI was longer in girls who matured early in comparison to those maturing late or at the average time.
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