AMBIENT TEMPERATURE AND SECONDARY SEX RATIO AT BIRTH: EVIDENCE FROM NORTH-CENTRAL NIGERIA

This study investigates the relationship between ambient temperature variability and the secondary sex ratio (SSR) at birth in Nasarawa State, Nigeria, from 2002 to 2023. The study aims to determine whether fluctuations in mean monthly temperature are associated with variations in male-to-female birth ratios and overall birth patterns. A longitudinal time-series design was adopted using climatic data obtained from the Nigerian Meteorological Agency and hospital birth records collected across the three senatorial districts of Nasarawa State. Mean monthly temperature was computed as the average of maximum and minimum monthly temperatures, while the secondary sex ratio was calculated as the ratio of male to female live births. Descriptive statistics, correlation analysis, seasonal decomposition, and multiple regression models were employed to examine temporal trends and statistical relationships. Findings reveal significant seasonal and inter-annual temperature variability, with a noticeable warming trend after 2010. The secondary sex ratio fluctuated around the biological norm, with periods of slight male predominance and near parity in recent years. Although a weak negative relationship was observed between conception-month temperature and total births, the association was not statistically significant. Overall, ambient temperature variability showed limited direct influence on sex ratio outcomes. The study concludes that while temperature variability contributes to seasonal birth fluctuations, broader socioeconomic and health-related factors likely play more substantial roles in shaping sex ratio dynamics. It is recommended that future research incorporate monthly conception data and advanced multivariate modelling to better isolate environmental effects on reproductive outcomes.