Analysis of air temperature influence on mortality in Tehran

A direct relationship exists between air temperature and seasonal and daily variations of mortality. Stressor effect of temperature decrease and increase has a significant increasing impact on death rate. Quantification of the relationship between daily mortality and air temperature is useful as a fundamental policy for accuracy enhancement of temperature decrease and increase warning system. The objective of this study was determination of the relationship between temperature and death rate and the Temperature Minimum Mortality (TMM) in Tehran during the period 2002-2005. In a descriptive and analytical study, we statistically analyzed the relationship between temperature and number of total deaths as well as deaths due to cardiovascular diseases, cerebrovascular accidents, and respiratory diseases. Studied population was the reference population for mortality in Tehran from which a 4-year sample of daily mortality was drawn for years 2000 to 2005. Relationship between daily death numbers and daily temperature averages was V-shaped during the studied period. TMM for Tehran was calculated as 28.5°C. The more different the temperature was form the TMM, the more was the death rate. There was a strong and significant correlation between air temperature and mortality rate, especially with average monthly mortality rate. Determination coefficient was 0.76 with a 99% confidence level. The highest number of deaths had occurred in the cold months of the year (December, January, and February). The more decrease in temperature had occurred, the more had increased the mortality. Increase in cardiovascular diseases, cerebrovascular accidents, and respiratory diseases mortality rates during the cold months further clarifies this relationship. Amongst 22 zones of Tehran’s Municipality, zones 9, 6, and 12 had the highest death rates.