The effect of cold and heat waves on mortality in Urmia a cold region in the North West of Iran.

Few studies have investigated the different extreme temperature effects (heat-cold) of one geographical location at the same time in Iran. This study was conducted to assess the impact of heat and cold waves on mortality in Urmia city, which has a cold and mountainous climate. Distributed Lag Non-linear Models combined with a quasi-Poisson regression were used to assess the impact of heat (HW) and cold waves (CW) on mortality in subgroups, controlled for potential confounders such as long-term trend of daily mortality, day of week effect, holidays, mean temperature, humidity, wind speed and air pollutants. The heat/cold effect was divided into two general categories A-main effect (the effect caused by temperature), B-added effect (the effect caused by persistence of extreme temperature). Results show that there was no relation between HW and respiratory and cardiovascular death, but in main effects, HW significantly increased, the risk of Non-Accidental Death (NAD) in lag 0 (Cumulative Excess Risk (CER)  = 31(CI; 4-65)). Also in added effects, HW had a significant effect on NAD (CER  = 31(CI; 5, 51), CER  = 26(CI; 6, 48)). There was no relation between CW and respiratory death and cardiovascular death, but in added effects, CW significantly decreased, the risk of non-accidental death in initial lags (CER  = -19 (CI; -35, -2)). It seems that high temperatures and heat waves increase the risk of non-accidental mortality in northwest of Iran.