Impact of temperature and air pollution on cardiovascular disease and death in Iran: A 15-year follow-up of Tehran Lipid and Glucose Study.

In this, the first study to be conducted in the Middle East and North Africa (MENA) on the subject, we examined the impact of temperature and air pollution on cardiovascular disease (CVD) and all-cause mortality. The Tehran Lipid and Glucose Study followed 9731 participants, aged ≥30years (men=4409), during the period 1999-2014, reporting 1350 CVDs (men=796) and 725 deaths (men=447). Air pollution level was measured using the air quality index (AQI). Data were analyzed using the distributed lag nonlinear model, with 30°C temperature and AQI=50 minimum risk values, as the relative risks' (RR) reference values. Although for the whole sample, no significant effect of air pollution was observed on CVD, for the under 60year olds, two significant peaks occurred in AQI=180 at lags 2 and 6days (RR=1.94, 95% CI: 1.02-3.67 and 2.06, 95% CI: 1.09-3.88, respectively). Temperature had no significant effect on CVD, yet the closest case to significance happened at 36°C and lag 5days (RR=1.43, 95% CI: 0.97-2.11), for ages ≥60y. The largest significant effects of air pollution on death, occurred in AQI=180 and lag 1day (RR=2.40, 95% CI: 1.0.-5.59 and 3.29, 95% CI: 1.15-9.36, for the whole sample and the <60year olds, respectively). Interestingly, for those aged over 60years, the peak belonged to AQI=180 and lag 7days (RR=2.16, 95% CI: 1.11-4.19). Regarding the effect of temperature on death among the whole sample, the highest risk was for 6°C and lag 0 (RR=3.91, 95% CI: 1.12-13.61). For the ≥60year olds, it occurred in 9+ and lag 0 (RR=6.81, 95% CI: 1.69-27.44), though notably, the peak went to -3°C and lag 3 (RR=5.69, 95% CI: 1.12-28.87), for those aged <60years. Overall, the effect of low temperature on death had the highest risk, for the over 60-year-olds, without any lag. Moreover, the <60-year-olds were the most vulnerable group to air pollution with a one day lag, in terms of mortality risk.