Maybe Next Month? Temperature Shocks and Dynamic Adjustments in Birth Rates

Area of Science:

• Environmental Health
• Reproductive Epidemiology
• Climate Change Impacts

Background:

• Rising global temperatures present potential risks to human health and reproduction.
• Previous research has linked extreme heat to reduced fertility, but mechanisms remain debated.
• Understanding the nuanced effects of temperature on birth rates is crucial for public health planning.

Purpose of the Study:

• To quantify the impact of temperature shocks on U.S. birth rates from 1931-2010.
• To investigate the temporal dynamics of fertility changes following heat exposure.
• To differentiate between reproductive health and sexual activity as pathways for heat's fertility effects.

Main Methods:

• Analysis of U.S. birth data spanning nine decades (1931-2010).
• Statistical modeling to assess the relationship between daily mean temperature and subsequent birth rates.
• Examination of birth timing shifts to understand population-level adaptive strategies.

Main Results:

• Mean temperatures exceeding 80°F were associated with a significant decline in birth rates 8-10 months later.
• A partial rebound in births was observed in the months following the initial decline, indicating conception month shifting.
• Evidence suggests high temperatures primarily impact reproductive health rather than sexual activity.

Conclusions:

• High temperatures negatively affect U.S. birth rates, with effects mediated through reproductive health.
• Population-level shifts in conception timing partially mitigate the fertility costs of heat.
• Air conditioning adoption may substantially offset the adverse reproductive outcomes associated with hot weather.