Mortality risks during extreme temperature events (ETEs) using a distributed lag non-linear model

This study investigates the relationship between all-cause mortality and extreme temperature events (ETEs) from 1975 to 2004. For 50 U.S. locations, these heat and cold events were defined based on location-specific thresholds of daily mean apparent temperature. Heat days were defined by a 3-day mean apparent temperature greater than the 95th percentile while extreme heat days were greater than the 97.5th percentile. Similarly, calculations for cold and extreme cold days relied upon the 5th and 2.5th percentiles. A distributed lag non-linear model assessed the relationship between mortality and ETEs for a cumulative 14-day period following exposure. Subsets for season and duration effect denote the differences between early- and late-season as well as short and long ETEs. While longer-lasting heat days resulted in elevated mortality, early season events also impacted mortality outcomes. Over the course of the summer season, heat-related risk decreased, though prolonged heat days still had a greater influence on mortality. Unlike heat, cold-related risk was greatest in more southerly locations. Risk was highest for early season cold events and decreased over the course of the winter season. Statistically, short episodes of cold showed the highest relative risk, suggesting unsettled weather conditions may have some relationship to cold-related mortality. For both heat and cold, results indicate higher risk to the more extreme thresholds. Risk values provide further insight into the role of adaptation, geographical variability, and acclimatization with respect to ETEs.

The influence of heat and cold waves on mortality in Russian subarctic cities with varying climates

Publications on ambient temperature-related mortality among Arctic or subarctic populations are extremely rare. While circumpolar areas cover large portions of several European countries, Canada, and the USA, the population of these territories is relatively small, and the data needed for statistical analysis of the health impacts of extreme temperature events are frequently insufficient. This study utilizes standard time series regression techniques to estimate relative increases in cause- and age-specific daily mortality rates during heat waves and cold spells in four Russian cities with a subarctic climate. The statistical significance of the obtained effect estimates tends to be greater in the continental climate than in the marine climate. A small meta-analysis was built around the obtained site-specific health effects. The effects were homogeneous and calculated for the selected weather-dependent health outcomes. The relative risks of mortality due to ischemic heart disease, all diseases of the circulatory system, and all non-accidental causes during cold spells in the age group ≥ 65 years were 1.20 (95% CI: 1.11-1.29), 1.14 (1.08-1.20), and 1.12 (1.07-1.17), respectively. Cold spells were more harmful to the health of the residents of Murmansk, Archangelsk, and Magadan than heat waves, and only in Yakutsk, heat waves were more dangerous. The results of this study can help the public health authorities develop specific measures for the prevention of excess deaths during cold spells and heat waves in the exposed subarctic populations.

Interannual variability of heat waves over the Korean Peninsula based on integrated approach

Heat waves can provide detrimental impacts on human society and the environmental system, and thus have received substantial attention in scientific research. Since heat waves are relevant to a wide range of stakeholders, definitions for heat wave events vary in terms of threshold values, durations, and utilized variables. While there is a value in this diversity of perspectives, the various definitions often complicate the assessment of heat wave risk, thereby underscoring the improved utility of a unified definition. In this study, we examine the interannual variability of heat wave patterns by using a proposed copula-based framework. From five observed temperature-related variables, this study first evaluates the individual changes of fifteen previously published heat wave indices focused on heat wave events across the Korean Peninsula for the last 49 years (1973-2021). We then extract the integrated signals to understand the overall trend patterns using the multiple heat wave indices. Results indicate that different heat wave definitions present distinctive attributes (e.g., in the magnitude of temporal changes) depending on the locations, implying that the diversity of heat wave definitions leads to potentially inconsistent conclusions. Using the integrated analysis, we identify that the expected heat wave day has increased across the majority of the regions in the Korean Peninsula. To be specific, substantial increases are shown in North Korea, while rapid increases in heat wave events have been observed after the year 2010 over South Korea. Finally, through the sensitivity analysis, we demonstrate the importance of choosing the heat wave definition in the integrated analysis.

Extreme temperature events, functional dependency, and cardiometabolic multimorbidity: Insights from a national cohort study in China

BACKGROUND

Extreme temperature events (ETEs), including heatwaves and cold spells, are attracting increasing attention because of their impacts on human health. However, the association between ETEs and cardiometabolic multimorbidity (CMM) and the role of functional dependency in this relationship remain unclear.

METHODS

A prospective cohort study was conducted using data from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2020, considering 12 definitions each for heatwaves and cold spells, and three levels of functional dependency. Mixed Cox models with time-varying variables were used to comprehensively assess the independent and combined effects of ETEs and functional dependency on CMM. Additionally, subgroup analyses were conducted to investigate whether the relationship between ETEs and CMM was modified by the baseline characteristics.

RESULTS

Heatwave and cold spell exposures were associated with an increased risk of CMM (HR range: 1.028-1.102 and 1.046-1.187, respectively). Compared to participants with normal functional abilities, the risk of CMM increased with higher levels of functional dependency (HR range: 1.938-2.185). ETEs exposure and functional dependency are jointly associated with CMM risk. Participants with high-intensity ETEs exposure and high functional dependency had the greatest risk of developing CMM. Participants aged 60 and above were more susceptible to the effects of ETEs on CMM. Additionally, urban residents and those in northern regions were more vulnerable to heatwaves.

CONCLUSION

Both ETEs exposure and functional dependency increase the risk of developing CMM. Participants with functional dependency exposed to high-intensity ETEs faced the highest risk of developing CMM. These findings highlight the significant impact of ETEs on CMM and the importance of protecting vulnerable populations during periods of extreme temperature.

Exposure to greenness modifies the association between extreme temperature events and ischemic stroke recurrence in Tianjin, China

Few studies have found an association between extreme temperature events and an increased risk of recurrent ischemic stroke (IS). We examined associations between extreme temperature events (heat waves, cold spells) and recurrent IS risk in Tianjin, China (2019-2020), using a time-stratified case-crossover design, while evaluating greenness's moderating role. Significant heat wave effects peaked at lag 8, with severe intensity events increasing IS recurrence risk by 39.8% (OR = 1.398, 95% CI:1.032-1.894). Cold spell impacts peaked at lag 3, with moderate intensity cold spells elevating risk by 20.3% (OR = 1.203, 95% CI: 1.052-1.377) and severe intensity cold spells elevating risk by 98.2% (OR = 1.982, 95% CI: 1.407-2.791). Greenness modified these associations: low-greenness areas strengthened heat wave effects(lag9:OR = 2.309,95%CI:1.024-5.209) but weakened cold spell impacts(OR = 1.557,95%CI:1.037-2.340), whereas high-greenness areas attenuated heat wave links(lag8:OR = 1.402,95%CI:1.022-1.924) and nullified cold spell associations. Age and sex disparities emerged - younger individuals and males showed higher susceptibility to heat waves, while older individuals and males were more vulnerable to cold spells. The findings highlight greenness as a potential modifier of extreme temperature events-related IS recurrence risks and underscore demographic-specific vulnerabilities.

Extreme temperature events and dementia mortality in Chinese adults: a population-based, case-crossover study

BACKGROUND

The effect of exposure to extreme temperature events (ETEs) on dementia mortality remains largely unknown. We aimed to quantify the association of ETE exposure with dementia mortality.

METHODS

We conducted a population-based, case-crossover study among 57 791 dementia deaths in Jiangsu province, China, during 2015-20. Daily mean temperatures were extracted from a validated grid dataset at each subject's residential address, and grid-specific exposures to heat wave and cold spell were assessed with a combination of their intensity and duration. We applied conditional logistic regression models to investigate cumulative and lag effects for ETE exposures.

RESULTS

Exposure to ETE with each of all 24 definitions was associated with an increased odds of dementia mortality, which was higher when exposed to heat wave. Exposure to heat wave (daily mean temperature ≥95th percentile, duration ≥3 days (d); P95_3d) and cold spell (≤5th percentile, duration ≥3 d; P5_3d) was associated with a 75% (95% CI: 61%, 90%) and 30% (19%, 43%) increase in odds of dementia mortality, respectively. Definitions with higher intensity were generally associated with a higher odds of dementia mortality. We estimated that 6.14% of dementia deaths were attributable to exposure to heat wave (P90_2d) and cold spell (P10_2d). No effect modifications were observed by sex or age, except that the association for heat wave was stronger among women.

CONCLUSIONS

Exposure to both heat wave and cold spell was associated with an increased odds of dementia mortality. Our findings highlight that reducing individual ETE exposures may be helpful in preventing deaths from dementia, especially among women in summer.

Short-term exposure to PM2.5 constituents, extreme temperature events and stroke mortality

BACKGROUND

Fine particulate matter (PM2.5) pollution and extreme temperature events (ETEs) are main environmental threats to human health. Elevated stroke mortality has been growingly linked to PM2.5 mass exposure, while its relationship with PM2.5 constituents was extensively unstudied across the globe. Additionally, no prior assessments have investigated the interactive effects of PM2.5 constituents and ETEs on stroke mortality.

METHODS

Province-wide records of 320,372 stroke deaths collected in eastern China during 2016-2019 were analyzed using an individual-level time-stratified case-crossover design. Daily gridded estimates of PM2.5 mass and its major constituents (i.e., black carbon [BC], organic matter [OM], ammonium [NH4+], sulfate [SO42-], and nitrate [NO3-]) were assigned to stroke cases on case days and control days at the residential address. We assessed 12 ETEs defined by multiple combinations of air temperature thresholds (2.5-10th percentiles for cold spell, 90-97.5th percentiles for heat wave) and durations (2-4 days). Conditional logistic regression model was applied to investigate associations of short-term exposure to PM2.5 constituents and ETEs with stroke mortality. Odds ratio and its 95% confidence interval (CI) were assessed for an interquartile range (IQR) increase in each PM2.5 constituent and on ETEs days compared with non-ETEs days. Additive interactive effects were quantitatively evaluated via relative excess odds due to interaction (REOI), attributable proportion due to interaction (AP), and synergy index (SI).

RESULTS

Elevated overall stroke mortality was significantly related to PM2.5 constituents, with the largest odds observed for NO3- (1.04, 95% CI: 1.03-1.04, IQR = 11.25 μg/m3), followed by OM (1.03, 1.03-1.04, IQR = 7.97 μg/m3), NH4+ (1.03, 1.02-1.04, IQR = 6.66 μg/m3), BC (1.03, 1.02-1.03, IQR = 1.41 μg/m3), and SO42- (1.03, 1.02-1.03, IQR = 6.67 μg/m3). Overall, higher risks of stroke mortality were identified in analyses using more rigorous thresholds and lengthened durations of ETEs definitions, ranging from 1.19 (1.17-1.21) to 1.55 (1.51-1.60) for heat wave, and 1.03 (1.02-1.05) to 1.11 (1.08-1.15) for cold spell, respectively. We observed consistent evidence for the synergistic effects of heat wave and PM2.5 constituents on both ischemic and hemorrhagic stroke mortality, where compound exposures to heat wave and secondary inorganic aerosols (i.e., NO3-, SO42-, and NH4+) posed greater increases in risk (0.23< REOI <0.81, 0.16< AP <0.39, and 2.63< SI <8.19).

CONCLUSIONS

Short-term exposure to both PM2.5 constituents and ETEs were associated with heightened stroke mortality, and heat wave may interact synergistically with PM2.5 constituents to trigger stroke deaths.

Interaction between Extreme Temperature Events and Fine Particulate Matter on Cardiometabolic Multimorbidity: Evidence from Four National Cohort Studies

Accumulating evidence linked extreme temperature events (ETEs) and fine particulate matter (PM2.5) to cardiometabolic multimorbidity (CMM); however, it remained unknown if and how ETEs and PM2.5 interact to trigger CMM occurrence. Merging four Chinese national cohorts with 64,140 free-CMM adults, we provided strong evidence among ETEs, PM2.5 exposure, and CMM occurrence. Performing Cox hazards regression models along with additive interaction analyses, we found that the hazards ratio (HRs) of CMM occurrence associated with heatwave and cold spell were 1.006-1.019 and 1.063-1.091, respectively. Each 10 μg/m3 increment of PM2.5 concentration was associated with 17.9% (95% confidence interval: 13.9-22.0%) increased risk of CMM. Similar adverse effects were also found among PM2.5 constituents of nitrate, organic matter, sulfate, ammonium, and black carbon. We observed a synergetic interaction of heatwave and PM2.5 pollution on CMM occurrence with relative excess risk due to the interaction of 0.999 (0.663-1.334). Our study provides novel evidence that both ETEs and PM2.5 exposure were positively associated with CMM occurrence, and the heatwave interacts synergistically with PM2.5 to trigger CMM.

The impact of different types of extreme temperature events on mental disorders: A case-crossover study in Anhui Province, China

BACKGROUND

Extreme temperatures are expected to be more frequent, intense, and complex in the context of climate change. However, epidemiologic evidence about associations between extreme temperature and mental disorders is limited.

METHODS

We conducted a case-crossover study in Anhui Province, China, focusing on outpatients diagnosed with mental and behavioral disorders (ICD-10 codes: F00-F99), further classified into schizophrenia (F20-F21), depression (F32-F33), and anxiety (F40-F41). Defining the day of each outpatient visit to the Anhui Mental Health Center as the case day, a total of 762,895 case days and 3,362,574 control days were included in the study, covering the period from 2019 to 2021. Each subject was geocoded based on their home address and matched with environmental exposures, including meteorological data and air pollutant data sourced from the CN05.1 and the TAP dataset, respectively. Extreme temperature events were categorized into heat and cold extremes, further divided into daytime, nighttime, and compound extremes.

RESULTS

Among the outpatient visits for mental disorders included in this study, the proportions were schizophrenia (28.9 %), depression (23.9 %), and anxiety (18.5 %). Exposure to extreme heat and cold was associated with increased risks of outpatient visits for mental disorders, with odds ratios (ORs) of 2.23 (95 %CI: 2.16-2.30) and 1.95 (95 %CI: 1.89-2.01), respectively. Compound heat extremes posed the highest risk of mental disorders (OR = 1.17, 95 %CI: 1.13-1.22), followed by nighttime (OR = 1.11, 95 %CI: 1.08-1.14) and daytime heat (OR = 1.05, 95 %CI: 1.04-1.07). Notably, the risk of mental disorders significantly elevated with the increased intensity and duration of extreme heat events. Besides, extreme heat was strongly associated with higher risks of depression, schizophrenia and anxiety, while extreme cold was notably linked to schizophrenia.

CONCLUSION

These findings indicate a significant correlation between extreme temperature exposure and elevated mental disorder risks, emphasizing the urgent need to address increased mental health risks posed by extreme temperatures in the changing climate.

Climate change and air pollution can amplify vulnerability of glucose metabolism: The mediating effects of biological aging

Climate change and air pollution pose significant global health threats, including impacts on diabetes risk; however, their long-term effects on insulin resistance (IR), a key determinant in diabetes pathophysiology, remain unclear. This study investigated whether exposure to heatwaves, temperature fluctuations, and warm-season ozone (O3) contributes to or exacerbates IR and explored the potential mediating role of biological aging. The study enrolled 6901 participants and assessed both traditional and novel IR indicators: estimated glucose disposal rate (eGDR), triglyceride-glucose (TyG) index, triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-c), metabolic score for IR (METS-IR), TyG-body mass index (TyG-BMI), TyG-waist circumference (TyG-WC), waist-to-height ratio (WHtR), TyG-WHtR, and lipid accumulation product (LAP). Ordinary least squares regression models were applied to evaluate the long-lasting effects of heatwaves, temperature fluctuation, and warm-season O3 on IR, incorporating Huber-White robust standard errors for model stability. Causal mediation analysis was utilized to investigate the mediating effects of biological aging. We found that exposure to heatwaves and higher concentrations of warm-season O3 was associated with elevated IR levels, with males, smokers, drinkers, and low-income individuals being more vulnerable. Accelerated biological aging (including body age, metabolomic aging rate, etc.) could significant mediate the long-lasting effects of heatwaves and warm-season O3. Our findings suggest that climate change and air pollution could amplify the vulnerability of glucose metabolism, particularly in males, smokers, drinkers, and individuals with low-income. More importantly, our findings reveal the importance of mitigating biological aging to prevent IR in the future, as global diabetes prevalence escalates rapidly.

Extreme temperature events, "Life's Essential 8", and prevalence of chronic kidney disease: A nationally representative surveillance in China

The population disease burden caused by extreme temperature events has been increasing. However, research on the long-term effects of extreme temperature events on chronic kidney disease (CKD), as well as the combined effects with individual behaviors and metabolic factors is still lacking. Based on 176,874 participants from the most recent nationally representative surveillance on CKD and validated high spatial resolution (0.1°) remote-sensing products, this study investigated the associations between extreme temperature events in the preceding five years before investigation and CKD (defined by reduced renal function or albuminuria) prevalence. We also investigated the associations between "Life's Essential 8", a recognized scale to evaluate overall cardiovascular health (CVH) based on individual behaviors and metabolic indicators and CKD prevalence, as well as its combined effects with extreme temperature events. One additional day of heat waves and cold spells per year was associated with increased ORs of CKD [1.10 (95 % CI: 1.08, 1.11) and 1.07 (95 % CI: 1.05, 1.09), respectively]. Meanwhile, per standard deviation (SD) increment in health behavior score (SD = 16.1), health factor score (SD = 18.4), and overall CVH score (SD = 12.4) were associated with decreased ORs of CKD [0.92 (95 % CI: 0.90, 0.93), 0.60 (95 % CI: 0.59, 0.61), and 0.64 (95 % CI: 0.63, 0.65, respectively]. Relative to higher heat wave & lower CVH score group, the ORs of CKD were 0.87 (95 % CI: 0.84, 0.90), 0.51 (95 % CI: 0.48, 0.53), and 0.42 (95 % CI: 0.40, 0.44) in lower & lower, higher & higher, and lower & higher group, respectively. Our findings underscore the importance of considering the synergistic effects of individual behavioral and metabolic factors for strategies to mitigate the impacts of climate change on CKD.

Reduced primary productivity and notable resilience of phytoplankton community in the coastal water of southern China under a marine heatwave

Increasing frequency, intensity and duration of marine heatwaves (MHWs) are supposed to affect coastal biological production in different regions to different extents. To understand how MHWs impact coastal primary productivity and community succession of phytoplankton and assess the changes in resilience of phytoplankton communities, we conducted a mesoscale enclosure experiment simulating a MHW in the coastal water of southern China. After 8 days of the MHW (+3 °C) treatment, community biomass was significantly lower than the control's, and primary productivity per volume of water was reduced by about 56%. Nevertheless, the phytoplankton community retrieved its biomass and primary productivity after the temperature was subsequently reset to that of the control. Although the MHW treatment decreased the abundance of diatom and increased the percentages of Synechococcus and Prasinophytes, the main phytoplankton functional types showed positive resilience that allowed the recovery of the phytoplankton community after the MHW. Our results indicate that key phytoplankton functional types in the southern coastal waters of China exhibited significant resilience, recovery, and temporal stability under the influence of the marine MHW by 3 °C rise. However, reduced primary productivity during the MHW period, along with decreased biomass density, might significantly influence secondary producers. In addition, the altered phytoplankton community structure may affect coastal food web processes at least during the MHW period.

Variation characteristics of extreme climate events in Southwest China from 1961 to 2017

Climate change is increasing the intensity of extreme climate events. Significant impacts of extreme climate events on human society and ecosystem have occurred in many places of the world, for example, Southwest China (SWC). In this study, the daily temperature and precipitation data from 438 meteorological stations are used to analyze the variation characteristics of extreme climate events in the SWC from 1961 to 2017. The annual extreme warm events show a significant increasing trend at 99% confidence level at most stations, and a few stations with a decreasing trend are mainly located in the southern Sichuan Province, the northern Yunnan Province and the western Guizhou Province. Meanwhile, the annual extreme cold events show a significant decreasing trend at 99% confidence level at most stations, and a few stations with an increasing trend are mainly distributed in the Sichuan Basin. Both the annual extreme heavy precipitation indexes and rainstorm indexes show nonsignificant increasing trends, but they differ greatly in the spatial distribution. These indexes in the western Tibet, Chongqing and most parts of Guizhou show significant increasing trends at 95% confidence level, while those in the central Sichuan and southeastern Yunnan show significant decreasing trends. The percentage of extreme heavy precipitation shows a significant increasing trend at 99% confidence level, especially in the northeastern Sichuan, the central-eastern Guizhou and the central Yunnan. Overall, under the background of global warming, the extreme warm events in SWC increase significantly from 1961 to 2017, and the extreme cold events decrease significantly. The variation trends of extreme precipitation events differ greatly in different regions, and the percentage of extreme heavy precipitation increases significantly.

Effects of extreme climate events and child mortality on total fertility rate in Bangladesh

Floods, storms, and temperature extremes are examples of extreme weather events that have a substantial influence on a country's demographic dynamics, including migration, fertility, and mortality. Changes in population size, composition, and distribution may result from these occurrences. This study, which spans the years 1966-2018, looks at how Bangladesh's total fertility rate (TFR) is affected by extreme weather events and child mortality, including neonatal, infant, male infant, and under-five mortality. We use data from secondary publicly accessible sources, such as the World Bank and The Emergency Events Database (EM-DAT), and we investigate the correlations using the autoregressive integrated moving average model (ARIMA), complemented by bivariate and multivariable analyses. Our findings from the univariate analysis are noteworthy. Total extreme climate events (β = -0.345, 95 % CI: 0.510, -0.180), as well as individual extreme climate events, such as extreme temperatures (β = -1.176, 95 % CI: 1.88, -0.47), floods (β = -0.644, 95 % CI: 1.0729, -0.216), and storms (β = -0.351, 95 % CI: 0.63159, -0.07154), exhibited negative associations with the TFR. Additionally, factors such as contraceptive prevalence rate (CPR) (β = -0.085, 95 % CI: 0.09072, -0.07954) and gross national income (GNI) per capita (β = -0.003, 95 % CI: 0.0041123, -0.0024234) were negatively correlated with the TFR. Conversely, various categories of child mortality, namely, infants (β = 0.041, 95 % CI: 0.040474, 0.042748), males (β = 0.038, 95 % CI:0.037719, 0.039891), and under-five (β = 0.026, 95 % CI:0.025684, 0.026979) - are positively associated with TFR. Controlling for two pivotal confounding factors, time and GNI per capita, yielded consistent results in the multivariate analysis. These findings provide insight on the dual impact of extreme weather events, which can reduce TFR while also raising it through infant mortality. This phenomena may be due to the increased vulnerability of younger children in climate-event-prone areas, prompting parents to seek additional children as both a replacement for lost offspring and an insurance mechanism against future child loss.