Comparison of Bio-meteorological index and temperature linked mortality: A case study from Ahmedabad city, India

The traditional approaches rely solely on temperature measures to assess heat-related health risks; but there is a growing trend towards using bio-meteorological indices for a more comprehensive evaluation. However, the adoption of bio-meteorological indices in developing countries is considerably limited. Therefore, this study compares bio-meteorological index, the maximum Universal Thermal Climate Index (UTCI_max) with single-exposure maximum temperature (Tmax) for assessing heat-related mortality risks in Ahmedabad city of India. Distributed Lag Non-Linear Model (DLNM) was used to estimate the relative risk (RR) of all-cause mortality with 95% confidence interval (CI) for a maximum lag of 14 days, using data from 2002 to 2018. Additionally, the study also checked the effectiveness of the Heat Action Plan (HAP) in the city by employing two matrices. Both maximum UTCI _max and T_max exposure-response curves showed similar trends and comparable heat-related mortality risks. While, UTCI_max, which also account for the effects of wind speed, solar radiation, and clothing achieved a better fit (Akaike weights). Females were more sensitive to heat under both indices. Analysis of pre- and post-HAP periods showed reduced immediate heat mortality risk across various temperature thresholds for T_max. However, this reduction for UTCI_max was only evident during extreme heat stress, suggesting limitations of using a single-exposure. Moreover, these positive mitigating effects were not observed for longer lag days and for moderate heat stress scenarios. Our findings emphasize the need for considering additional indices like UTCI _max alongside temperature for a more comprehensive evaluation. This approach can help in more accurate risk assessments and effective heat-health alerts in developing countries like India.