An Abrupt Mid-1970s Shift in UK Birth Seasonality and Its Implications for Chronobiological Studies.

ABSTRACT: We present a comprehensive analysis of the historical fluctuations and rephasing of seasonal birth rates in the United Kingdom from 1955 to 2015. We analyzed monthly live-birth records for England and Wales together with national photoperiod and surface-temperature series to track the annual rhythm of human reproduction. Fast Fourier transforms confirmed a robust 12-month component across the entire record, but breakpoint tests located a sharp phase shift in 1974-1976. Before this transition, peak conceptions clustered tightly around the summer solstice and yielded a stable March birth maximum. After 1976, the rhythm decoupled: the spring peak in births collapsed, a secondary autumn peak emerged, and inter-annual phase variability more than doubled. Cross-correlation analyses showed that,

SUBMITTER: Hearn TJ 

PROVIDER: S-EPMC12804422 | biostudies-literature | 2025 Nov

REPOSITORIES: biostudies-literature