Background: Cardiovascular disease is the leading cause of death worldwide. Existing studies on the association between temperatures and cardiovascular deaths have been limited in geographic zones and have generally considered associations with total cardiovascular deaths rather than cause-specific cardiovascular deaths. Methods: We used unified data collection protocols within the Multi-Country Multi-City Collaborative Network to assemble a database of daily counts of specific cardiovascular causes of death from 567 cities in 27 countries across 5 continents in overlapping periods ranging from 1979 to 2019. City-specific daily ambient temperatures were obtained from weather stations and climate reanalysis models. To investigate cardiovascular mortality associations with extreme hot and cold temperatures, we fit case-crossover models in each city and then used a mixed-effects meta-analytic framework to pool individual city estimates. Extreme temperature percentiles were compared with the minimum mortality temperature in each location. Excess deaths were calculated for a range of extreme temperature days. Results: The analyses included deaths from any cardiovascular cause (32 154 935), ischemic heart disease (11 745 880), stroke (9 351 312), heart failure (3 673 723), and arrhythmia (670 859). At extreme temperature percentiles, heat (99th percentile) and cold (1st percentile) were associated with higher risk of dying from any cardiovascular cause, ischemic heart disease, stroke, and heart failure as compared to the minimum mortality temperature, which is the temperature associated with least mortality. Across a range of extreme temperatures, hot days (above 97.5th percentile) and cold days (below 2.5th percentile) accounted for 2.2 (95% empirical CI [eCI], 2.1–2.3) and 9.1 (95% eCI, 8.9–9.2) excess deaths for every 1000 cardiovascular deaths, respectively. Heart failure was associated with the highest excess deaths proportion from extreme hot and cold days with 2.6 (95% eCI, 2.4–2.8) and 12.8 (95% eCI, 12.2–13.1) for every 1000 heart failure deaths, respectively. Conclusions: Across a large, multinational sample, exposure to extreme hot and cold temperatures was associated with a greater risk of mortality from multiple common cardiovascular conditions. The intersections between extreme temperatures and cardiovascular health need to be thoroughly characterized in the present day—and especially under a changing climate.

The nexus between prenatal greenspace exposure and low birth weight (LBW) remains largely unstudied in low- and middle-income countries (LMICs). We investigated a nationwide retrospective cohort of 4,021,741 live births (263,728 LBW births) across 31 provinces in Iran during 2013–2018. Greenness exposure during pregnancy was assessed using satellite-based normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). We estimated greenness-LBW associations using multiple logistic models, and quantified avoidable LBW cases under scenarios of improved greenspace through counterfactual analyses. Association analyses provide consistent evidence for approximately L-shaped exposure-response functions, linking 7.0–11.5% declines in the odds of LBW to each 0.1-unit rise in NDVI/EVI with multiple buffers. Assuming causality, 3931–5099 LBW births can be avoided by achieving greenness targets of mean NDVI/EVI, amounting to 4.4–5.6% of total LBW births in 2015. Our findings suggest potential health benefits of improved greenspace in lowering LBW risk and burden in LMICs.

Weather and climate play a significant role in human health. We are accustomed to affects the weather conditions. By increasing or decreasing the environment temperature or change of seasons, some diseases become prevalent or remove. This study investigated the role of temperature in cardiovascular disease mortality of city of Mashhad in the current decade and its simulation in the future decades under conditions of climate change. Cardiovascular disease mortality data and the daily temperatures data were used during (2004–2013) period. First, the correlation between cardiovascular disease mortality and maximum and minimum temperatures were calculated then by using General Circulation Model, Emissions Scenarios, and temperature data were extracted for the next five decades and finally, mortality was simulated. There is a strong positive association between maximum temperature and mortality (r= 0.83, P-value<0.01), also observed a negative and weak but significant association between minimum temperatures and mortality. The results obtained from simulation show increased temperature in the next decades in Mashhad and a 1 °C increase in maximum temperature is associated with a 4.27% (95%CI: 0.91, 7.00) increase in Cardiovascular disease mortality. By increasing temperature and the number of hot days the cardiovascular disease mortality increases and these increases will be intensified in the future decades. Therefore, necessary preventive measures are required to mitigate temperature effects with greater attention to vulnerable group.

Maternal ambient fine particulate matter (PM_2.5) has been linked with fetal low birthweight (LBW), while national causal evidence is limited, particularly in low- and middle-income countries. We used nationwide registry-based birth records of 3839531 singleton livebirths, with maternal age (MA) between 15 and 49 years, across 31 provinces in Iran from 2013 through 2018. Monthly gridded concentrations of ambient PM_2.5 during entire pregnancy were estimated through validated spatiotemporal models. We adopted traditional logistic/linear regression and double robust model (DRM) based on generalized propensity scores (GPS) to evaluate associations of maternal PM_2.5 exposure with LBW risk and birthweight change. MA-specific exposure-response functions were investigated using restricted cubic splines in both traditional and casual inference models. PM_2.5-attributable LBW burden were parallelly estimated, under the scenarios of achieving counterfactual exposure levels of multiple WHO interim targets. A total of 228655 LBW births were identified, and mean birthweight of was 3187 g. Both traditional and causal modelling approaches yielded consistently positive associations of maternal PM_2.5 exposure with increased LBW risk and reduced birthweight, but marginally larger effect estimates were seen under GPS-based DRM analyses. Specifically, a 10-μg/m³ increase in ambient PM_2.5 during the entire pregnancy was associated with the odds of 1.071 (95% confidence interval: 1.066, 1.076) for LBW and reduced birthweight of 8.9 (8.4, 9.4) g in GPS-based DRM analysis. MA-stratified analyses suggested non-linear exposure-response relationships of PM_2.5 exposure with both LBW (P_nonlinear <0.001) risk and birthweight change (P_nonlinear <0.001) over the exposure range of 17-104 μg/m³, with notably steeper slopes at low concentrations (<37.3 μg/m³). According to GPS-based DRM analysis, achieving the interim target level 1-3 of annual PM_2.5 (i.e., 35, 25, and 15 μg/m³) could avoid 5.5%-32.6% of overall LBW infants and birthweight loss of 7.0-57.6 g per livebirth during 2013-2018 in Iran. Our findings provided nationwide evidence of causality for elevated LBW risk and birthweight loss associated with maternal PM_2.5 exposure in Iran. Improving air quality through multisectoral efforts may avoid dramatic LBW burden to promote neonatal health later in life.