Effect of Air Temperature and Universal Thermal Climate Index on Respiratory Diseases Mortality in Mashhad, Iran.

OBJECTIVE: Climatic factors with desired and sometimes undesired effects lead to changes in the human body, such as hypothermia, influenza, heart disease, stroke, asthma, etc. The present study investigates the role of temperature in respiratory mortality in Mashhad, Iran. MATERIALS AND METHODS: Among the respiratory mortality data, daily temperature, wind speed and relative humidity from 2004 to 2013 were used. First, Tmrt parameter was calculated through Ray Man software and the values of UTCI index were obtained using Bioklima software. Finally, the correlation between the thresholds of the above-mentioned index and temperature as well as mortality was calculated. In addition, the mortality risk ratio in all of these thresholds was calculated. RESULT: The results show that the UTCI index has changed from 32°C to 40°C in Mashhad. There is a strong and negative relationship between the maximum temperature (r = -0.90, P-value < 0.001) and mortality, and a positive relationship between the minimum temperature and mortality. In addition, the correlation between index and mortality shows that the highest positive and strong correlation is observed in negative temperature thresholds with cold stress. Thresholds with thermal stress are also inversely associated with mortality. The study of the mortality risk ratio in all thermal stress thresholds shows that in average cold stresses and a 10°C reduction, the mortality risk ratio increases by 1.36% in the significance level of 95%. CONCLUSION: Generally, mortality increases with decreasing temperature and increasing cold stresses and the mortality risk increases by 1.36% per 10°C reduction.