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Human birth seasonality and sunshine.
1bynehill@cableone.net
Summary
Seasonal birth patterns are linked to environmental light intensity (ELI). This study found increased ELI precedes conception periods, supporting the ELI/photoperiod hypothesis for human birth seasonality.
Area of Science:
- Human biology and environmental science
- Reproductive health and seasonality
Background:
- The environmental light intensity/photoperiod (ELI/PP) hypothesis links human birth seasonality to ambient light changes.
- Seasonal variations in births are observed globally, but the underlying drivers require further investigation.
Purpose of the Study:
- To test the ELI/PP hypothesis by examining the correlation between increased environmental light intensity and human conception periods.
- To analyze birth data across diverse global locations to assess the universality of the ELI/PP hypothesis.
Main Methods:
- Monthly birth data from nine global cities were correlated with corresponding monthly meteorological data.
- Birth data were adjusted for conception timing, month length, leap years, and annual deviations.
- Meteorological data were analyzed for a 1-2 month exposure period preceding conception.
Main Results:
- Strong positive correlations between preceding environmental light intensity and conception months were observed in most locations (e.g., Helsinki r=0.82, Hanoi r=0.93).
- Denver showed a moderate correlation (r=0.53), while Pretoria exhibited a negative correlation (r=-0.82), suggesting regional variations or confounding factors.
- The findings generally support the ELI/PP hypothesis, indicating a link between light exposure and conception timing.
Conclusions:
- Increased environmental light intensity appears to precede increased conception periods, supporting its role in human birth seasonality.
- While ELI/PP is a significant factor, other variables like atmospheric pollution may also influence seasonality.
- The ELI/PP hypothesis provides a strong framework but acknowledges that it may not be the sole determinant of reproductive seasonality.
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