Multimorbidity and emergency hospitalisations during hot weather

BACKGROUND

People with chronic diseases are a commonly listed heat-vulnerable group in heat-health action plans. While prior research identifies multiple health conditions that may increase vulnerability to ambient heat, there is minimal evidence regarding the implications of multimorbidity (two or more chronic diseases).

METHODS

From the statewide hospital registry of Queensland, Australia, we identified people aged ≥15 years who had emergency hospitalisation(s) between March 2004 and April 2016 and previously had 0, 1, 2, or ≥3 of five chronic diseases: cardiovascular disease, diabetes, mental disorders, asthma/COPD, and chronic kidney disease. We conducted time-stratified case-crossover analyses to estimate the odds ratio of hospitalisations associated with ambient heat exposure in people with different numbers, types, and combinations of chronic diseases. Ambient heat exposure was defined as a 5 °C increase in daily mean temperature above the median.

FINDINGS

There were 2,263,427 emergency hospitalisations recorded (48.7% in males and 51.3% in females). When the mean temperature increased, hospitalisation odds increased with chronic disease number, particularly in older persons (≥65 years), males, and non-indigenous people. For instance, in older persons with 0, 1, 2, or ≥3 chronic diseases, the odds ratios associated with ambient heat exposure were 1.00 (95% confidence interval: 0.96, 1.04), 1.06 (1.02, 1.09), 1.08 (1.02, 1.14), and 1.13 (1.07, 1.19), respectively. Among the chronic diseases, chronic kidney disease, and asthma/COPD, either existing alone, together, or in combination with other diseases, were associated with the highest odds of hospitalisations under ambient heat exposure.

INTERPRETATION

While individuals with multimorbidity are considered in heat-health action plans, this study suggests the need to consider specifically examining them as a distinct and vulnerable subgroup.

FUNDING

Wellcome.

The impact of climate change and related extreme weather on people with limb loss

The human health consequences of climate change and extreme weather events are well documented. Published literature details the unique effects and necessary adaptation planning for people with physical disabilities in general; however, the specific impacts and plans for people with limb loss have yet to be explored. In this article, we discuss the impacts related to threats due to heat, cold, severe storms, and power outages. We describe how climate change uniquely affects people with limb loss and underscore the need for rehabilitation care providers and researchers to: (1) study the health impacts of climate change on people with lower limb loss; (2) educate themselves and patients on the climate crisis and climate preparedness; (3) co-develop resiliency strategies with patients, governments, and community organizations to improve adaptive capacity; and (4) advocate for policy changes that will enact protections for this at-risk population.

The impact of extreme heat on older regional and rural Australians: A systematic review

INTRODUCTION

Extreme heat causes a major health burden, especially for older Australians.

OBJECTIVE

To assess the impact of extreme heat on older regional and rural Australians, including clinical presentations, social implications, and health-seeking behaviours and adaptations.

DESIGN

A systematic review and narrative synthesis.

FINDINGS

Ten articles were included in the review with research on this topic limited. Extreme heat causes an increase in mortality and ambulance dispatches for older rural Australians. Social connectedness is negatively affected by extreme heat due to cancellation of events and individuals becoming housebound. Air conditioning is the main cooling mechanism used, although cost is a major concern. Despite this, older rural populations display a depth of knowledge regarding practical behavioural responses to adapt to extreme heat. Studies show older rural Australians do not consider extreme heat to be a threat to health.

DISCUSSION

Further research needs to examine the role extreme heat may play in contributing to experiences of loneliness. Air conditioning cannot be the ultimate solution in responding to extreme heat due to cost and increased carbon emissions. The low-risk perception of extreme heat for older rural people may inform effective heat health warnings and effective use of primary health care in heat-health education. Listening to First Nations knowledge in dealing with heat may provide a powerful mechanism in which to protect health.

CONCLUSION

The extensive health effects of extreme heat highlights the necessity of further research and strengthening of services in preparation for an ageing rural population enduring climate change.

Ambient heat and diabetes hospitalizations: Does the timing of heat exposure matter?

BACKGROUND

Although ambient heat exposure is linked with diabetes mortality, the impacts of heat exposure on diabetes-related hospitalizations remain controversial. Previous research did not examine the timing of heat-diabetes associations and relation with comorbidities/risk factors.

OBJECTIVE

We examined the association between heat exposure and diabetes-related hospitalizations in the transitional and summer months and identified populations vulnerable to heat.

METHODS

We conducted a time-stratified case-crossover study. Data on diabetes hospital admissions (primary diagnosis of type 1 and type 2 diabetes, 2013-2020) were collected by the New York State (NYS) Department of Health under the state legislative mandate. We treated temperature and air pollutants as continuous variables and defined the heat exposure as per interquartile range (IQR, a measure between the 25th and 75th percentiles) increase of daily mean temperature. Conditional logistic regressions were performed to quantify the heat-diabetes associations after controlling for air pollutants and time variant variables. Multiplicative-scale interactions between heat and demographics/comorbidities/risk factors on diabetes hospitalizations were investigated.

RESULTS

Each IQR increase in temperature was associated with significantly increased risks for diabetes admissions that occurred immediately and lasted for an entire week during multi-day lags in the transitional month of May (ranges of excess risk: 3.1 %-4.8 %) but not in the summer (June-August) (ranges of excess risk: -0.3 %-1.3 %). The significant increases in the excess risk of diabetes were also found among diabetes patients with complications of neuronopathy (excess risk: 27.7 %) and hypoglycemia (excess risk: 19.1 %). Furthermore, the modification effects on the heat-diabetes association were significantly stronger in females, Medicaid enrollees, non-compliant patients, and individuals with comorbidities of atherosclerotic heart disease and old myocardial infarction.

CONCLUSIONS

Ambient heat exposure significantly increased the burden of hospital admissions for diabetes in transitional rather than summer months indicating the importance of exposure timing. Vulnerability to heat varied by demographics and heart comorbidity.

Impact of environmental factors on diabetes mortality: A comparison between inland and coastal areas

BACKGROUND

Diabetes mortality varies between coastal and inland areas in Shandong Province, China. However, evidence about the reasons for this disparity is limited. We assume that distinct environmental conditions may contribute to the disparities in diabetes mortality patterns between coastal and inland areas.

METHOD

Qingdao and Jinan were selected as typical coastal and inland cities in Shandong Province, respectively, with similar socioeconomic but different environmental characteristics. Data on diabetes deaths and environmental factors (i.e., temperature, relative humidity and air pollution particles with a diameter of 2.5 μm or less (PM2.5)) were collected from 2013 to 2020. Spatial kriging methods were used to estimate the aggregated diabetes mortality at the city level. A distributed lag non-linear model (DLNM) was used to quantify the possible cumulative and non-cumulative associations between environmental factors and diabetes mortality by age, sex and location.

RESULTS

In the coastal city (Qingdao), the maximum cumulative relative risks (RRs) of temperature and PM2.5 associated with diabetes deaths were 2.54 (95 % confidence interval (CI): 1.25-5.15), and 1.17 (95 % CI: 1.01-1.37) respectively, at lag 1 week. In the inland city (Jinan), only temperature exhibited significant cumulative associations with diabetes deaths (RR = 1.54, 95 % CI: 1.07-2.23 at 29 °C). Lower relative humidity (22 %-45 %) had a lag-specific association with diabetes deaths in inland areas at lag 3 weeks (RR = 1.33, 95 % CI: 1.03-1.70 at 22 %).

CONCLUSION

Despite the lower PM2.5 concentrations in the coastal location, diabetes mortality exhibited stronger links to environmental variables in the coastal city than in the inland city. These findings suggest that the control of air pollution could decrease the mortality burden of diabetes, even in the region with relatively good air quality. Additionally, the spatial estimation method is recommended to identify associations between environmental factors and diseases in studies with limited data.

China's public health initiatives for climate change adaptation

China's health gains over the past decades face potential reversals if climate change adaptation is not prioritized. China's temperature rise surpasses the global average due to urban heat islands and ecological changes, and demands urgent actions to safeguard public health. Effective adaptation need to consider China's urbanization trends, underlying non-communicable diseases, an aging population, and future pandemic threats. Climate change adaptation initiatives and strategies include urban green space, healthy indoor environments, spatial planning for cities, advance location-specific early warning systems for extreme weather events, and a holistic approach for linking carbon neutrality to health co-benefits. Innovation and technology uptake is a crucial opportunity. China's successful climate adaptation can foster international collaboration regionally and beyond.

Effects of Medications on Heat Loss Capacity in Chronic Disease Patients: Health Implications Amidst Global Warming

Pharmacological agents used to treat or manage diseases can modify the level of heat strain experienced by chronically ill and elderly patients via different mechanistic pathways. Human thermoregulation is a crucial homeostatic process that maintains body temperature within a narrow range during heat stress through dry (i.e., increasing skin blood flow) and evaporative (i.e., sweating) heat loss, as well as active inhibition of thermogenesis, which is crucial to avoid overheating. Medications can independently and synergistically interact with aging and chronic disease to alter homeostatic responses to rising body temperature during heat stress. This review focuses on the physiologic changes, with specific emphasis on thermolytic processes, associated with medication use during heat stress. The review begins by providing readers with a background of the global chronic disease burden. Human thermoregulation and aging effects are then summarized to give an understanding of the unique physiologic changes faced by older adults. The effects of common chronic diseases on temperature regulation are outlined in the main sections. Physiologic impacts of common medications used to treat these diseases are reviewed in detail, with emphasis on the mechanisms by which these medications alter thermolysis during heat stress. The review concludes by providing perspectives on the need to understand the effects of medication use in hot environments, as well as a summary table of all clinical considerations and research needs of the medications included in this review. SIGNIFICANCE STATEMENT: Long-term medications modulate thermoregulatory function, resulting in excess physiological strain and predisposing patients to adverse health outcomes during prolonged exposures to extreme heat during rest and physical work (e.g., exercise). Understanding the medication-specific mechanisms of altered thermoregulation has importance in both clinical and research settings, paving the way for work toward refining current medication prescription recommendations and formulating mitigation strategies for adverse drug effects in the heat in chronically ill patients.

Associations of cold exposure with hospital admission and mortality due to acute kidney injury: A nationwide time-series study in Korea

BACKGROUND

Emerging evidence supports an association between heat exposure and acute kidney injury (AKI). However, there is a paucity of studies on the association between cold exposure and AKI.

OBJECTIVE

We aimed to investigate the associations of cold exposure with hospital admission and mortality due to AKI and to explore whether these associations were influenced by age and sex.

METHODS

Information on daily counts of hospital admission and mortality due to AKI in 16 regions of Korea during the cold seasons (2010-2019) was obtained from the National Health Insurance Service (a single national insurer providing universal health coverage) and Statistics Korea. Daily mean temperature and relative humidity were calculated from hourly data obtained from 94 monitoring systems operated by the Korean Meteorological Administration. Associations of low temperatures (<10th percentile of daily mean temperature) and cold spells (≥2 consecutive days with <5th percentile of daily mean temperature) up to 21 days with AKI were estimated using quasi-Poisson regression models adjusted for potential confounders (e.g., relative humidity and air pollutants) with distributed lag models and univariate meta-regression models.

RESULTS

Low temperatures were associated with hospital admission due to AKI [relative risk (RR) = 1.12, 95 % confidence interval (CI): 1.09, 1.16]. Cold spells were associated with hospital admission (RR = 1.87, 95 % CI: 1.46, 2.39) and mortality due to AKI (RR = 4.84, 95 % CI: 1.30, 17.98). These associations were stronger among individuals aged ≥65 years than among those aged <65 years.

CONCLUSION

Our results underscore the need for the general population, particularly the elderly, physicians, and other healthcare providers to be more vigilant to cold exposure, given the risk of AKI. Government agencies need to develop specific strategies for the prevention and early detection of cold exposure-related AKI.

Urban-rural disparity in heatwave effects on diabetes mortality in eastern China: A case-crossover analysis in 2016-2019

Diabetics are sensitive to high ambient temperature due to impaired thermoregulation. However, available evidence on the impact of prolonged high temperature (i.e., heatwave) on diabetes deaths is limited and whether urban and rural areas differ in heatwave vulnerability remains unknown so far. A time-stratified case-crossover analysis was employed to estimate the association between heatwaves and diabetes deaths in 1486 districts (509 urban and 977 rural areas) of eastern China (Jiangsu Province), 2016-2019. For each decedent, residential heatwave exposure was measured by matching daily mean temperatures to the geocoded residential address. We adopted nine-tiered heatwave definitions incorporating intensity and duration. Stratified analyses by decedents' characteristics (gender, age, and education) were also conducted. During the study period, there were 18,685 deaths from diabetes (urban proportion: 36.95 %, p-value for urban-rural difference < 0.05). Heatwaves were associated with an increased risk of diabetes deaths, with greater and longer-lasting effects in rural areas than urban areas [e.g., rural odds ratio (OR): 1.19 (95 % confidence interval (CI): 1.14, 1.25) vs. urban OR: 1.09 (95 % CI: 1.05, 1.12)]. Risk of diabetes deaths increased with the intensity of heatwaves in rural areas (p-value for trend <0.01), but not in urban areas. Stratified analyses in rural areas suggested that females and less-educated people were more vulnerable to heatwave-related diabetes deaths. Our findings revealed the urban-rural disparity in the risk of diabetes deaths associated with heatwaves. Rural diabetics should be made aware of the increased death risk posed by heatwaves in the context of warming climate.

Adverse heat-health outcomes and critical environmental limits (Pennsylvania State University Human Environmental Age Thresholds project)

BACKGROUND

The earth's climate is warming and the frequency, duration, and severity of heat waves are increasing. Meanwhile, the world's population is rapidly aging. Epidemiological data demonstrate exponentially greater increases in morbidity and mortality during heat waves in adults ≥65 years. Laboratory data substantiate the mechanistic underpinnings of age-associated differences in thermoregulatory function. However, the specific combinations of environmental conditions (i.e., ambient temperature and absolute/relative humidity) above which older adults are at increased risk of heat-related morbidity and mortality are less clear.

METHODS

This review was conducted to (1) examine the recent (past 3 years) literature regarding heat-related morbidity and mortality in the elderly and discuss projections of future heat-related morbidity and mortality based on climate model data, and (2) detail the background and unique methodology of our ongoing laboratory-based projects aimed toward identifying the specific environmental conditions that result in elevated risk of heat illness in older adults, and the implications of using the data toward the development of evidence-based safety interventions in a continually-warming climate (PSU HEAT; Human Environmental Age Thresholds).

RESULTS

The recent literature demonstrates that extreme heat continues to be increasingly detrimental to the health of the elderly and that this is apparent across the world, although the specific environmental conditions above which older adults are at increased risk of heat-related morbidity and mortality remain unclear.

CONCLUSION

Characterizing the environmental conditions above which risk of heat-related illnesses increase remains critical to enact policy decisions and mitigation efforts to protect vulnerable people during extreme heat events.

Heat wave adaptation paradigm and adaptation strategies of community: A qualitative phenomenological study in Iran

BACKGROUND

Heat wave adaptation is a new concept related to experiencing heat. The present study aims at investigating a conceptual definition, that is, the mental framework of heat wave adaptation and its strategies.

MATERIALS AND METHODS

A phenomenological study was performed to explain the mental concept. At the same time with the data collection process, data analysis was also performed using Colaizzi method. Semi-structured interview method and purposeful sampling with maximum variety were used. Interviews were conducted with 23 different subjects in the community. The accuracy of the data was guaranteed using Lincoln & Guba scientific accuracy criteria.

RESULTS

The two main themes of the adaptation paradigm as well as its strategies were divided into the main categories of theoretical and operational concepts, as well as personal care measures and government measures. Under the category of individual measures, we obtained "clothing, nutrition, building, place of residence and lifestyle," and under the category of governance actions, the "managerial, research, health, organizational" subcategories were obtained.

CONCLUSION

According to the results of the conceptual-operational definition, heat wave adaptation is an active process and an effort to reduce the adverse effects of heat waves on individual and social life, and striking a balance that will not only result in individual awareness and actions that will lead to lifestyle changes, but also mostly requires integrated and comprehensive planning in the community. On the one hand, heat waves could not only be regarded as a threat or danger, but can also become an opportunity for the development of a community through identification and smart measures, and for adaptation, the community must take it as a risk. The community should have a plan in advance, apply the necessary rules and training, and use the new facilities and rules where necessary. This practical concept definition includes the main features of heat wave adaptation.

The Impact of Heatwaves on Mortality and Morbidity and the Associated Vulnerability Factors: A Systematic Review

BACKGROUND

This study aims to investigate the current impacts of extreme temperature and heatwaves on human health in terms of both mortality and morbidity. This systematic review analyzed the impact of heatwaves on mortality, morbidity, and the associated vulnerability factors, focusing on the sensitivity component.

METHODS

This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 flow checklist. Four databases (Scopus, Web of Science, EBSCOhost, PubMed) were searched for articles published from 2012 to 2022. Those eligible were evaluated using the Navigation Guide Systematic Review framework.

RESULTS

A total of 32 articles were included in the systematic review. Heatwave events increased mortality and morbidity incidence. Sociodemographic (elderly, children, male, female, low socioeconomic, low education), medical conditions (cardiopulmonary diseases, renal disease, diabetes, mental disease), and rural areas were crucial vulnerability factors.

CONCLUSIONS

While mortality and morbidity are critical aspects for measuring the impact of heatwaves on human health, the sensitivity in the context of sociodemographic, medical conditions, and locality posed a higher vulnerability to certain groups. Therefore, further research on climate change and health impacts on vulnerability may help stakeholders strategize effective plans to reduce the effect of heatwaves.

Association between extreme ambient heat exposure and diabetes-related hospital admissions and emergency department visits: A systematic review

Background and objectives

Diabetes is an increasing public health concern worldwide. The impact of extreme heat exposure on diabetes healthcare utilization such as diabetes-related hospital admissions and emergency department (ED) visits was understudied although extreme temperature exposure was linked with diabetes mortality. In addition, very few systematic reviews have been conducted in this field. This review aims to systematically evaluate the currently available evidence on the association between extreme ambient heat exposure and hospital admissions/ED visits for diabetes and the vulnerable population to heat extremes.

Methods

A systematic literature review was conducted by using the keywords/terms "ambient temperature or heatwave or heat wave or extreme temperature or high temperature effect " and "diabetes morbidity or diabetes hospital admissions or diabetes emergency room visits " for available publications until August 2022. The heat exposure was categorized into four groups using difference definitions. The outcomes were diabetes-related hospital admissions/ED visits. A meta-analysis was performed to estimate the pooled effects of relative risk (RR)/odds ratio (OR) and 95% confidence intervals (CI) for each of the associations of interest.

Results

Eighteen articles were selected from forty full-text, English written papers based on the inclusion and exclusion criteria. The overall pooled effect of excessive heat on diabetes, across all groups, was 1.045 (95% CI 1.024-1.066). The pooled effects for each exposure group were significant/borderline significant. Additionally, the pooled effect of the RR/OR was 1.100 (95% CI: 1.067-1.135) among adults aged 65 years or older. The most controlled confounders were air pollutants. The commonly listed limitation in those studies was misclassification of exposure.

Conclusions

The body of evidence supports that ambient extreme heat exposure is associated with diabetes-related hospital admissions/ED visits. Additionally, adults 65 years of age or older with diabetes are vulnerable to heat extremes. Future studies should consider controlling for various biases and confounders.

Ambient temperature and atmospheric pressure at discharge as precipitating factors in immediate adverse events in patients treated for decompensated heart failure

To investigate the relationship of ambient temperature and atmospheric pressure (AP) at patient discharge after an episode of acute heart failure (AHF) with very early post-discharge adverse outcomes. We analyzed 14,656 patients discharged after an AHF episode from 26 hospitals in 16 Spanish cities. The primary outcome was the 7-day post-discharge combined adverse event (emergency department -ED- revisit or hospitalization due to AHF, or all-cause death), and secondary outcomes were these three adverse events considered individually. Associations (adjusted for patient and demographic conditions, and length of stay -LOS- during the AHF index episode) of temperature and AP with the primary and secondary outcomes were investigated. We used restricted cubic splines to model the continuous non-linear association of temperature and AP with each endpoint. Some sensitivity analyses were performed. Patients were discharged after a median LOS of 5 days (IQR = 1-10). The highest temperature at discharge ranged from - 2 to 41.6 °C, and AP was from 892 to 1037 hPa. The 7-day post-discharge combined event occurred in 1242 patients (8.4%), with percentages of 7-day ED-revisit, hospitalization and death of 7.8%, 5.1% and 0.9%, respectively. We found no association between the maximal temperature and AP on the day of discharge and the primary or secondary outcomes. Similarly, there were no significant associations when the analyses were restricted to hospitalized patients (median LOS = 7 days, IQR = 4-11) during the index event, or when lag-1, lag-2 or the mean of the 3 post-discharge days (instead of point estimation) of ambient temperature and AP were considered. Temperature and AP on the day of patient discharge are not independently associated with the risk of very early adverse events during the vulnerable post-discharge period in patients discharged after an AHF episode.

Association between sub-daily exposure to ambient air pollution and risk of asthma exacerbations in Australian children

Short-term exposure to ambient air pollution is associated with risk of asthma attacks. We investigated the association between ultra-short-term exposure to air pollution and risk of childhood asthma exacerbations. Hourly data on emergency department visits (EDVs) for asthma in children during 2013-2015 in Brisbane, Australia, were obtained. We undertook time-stratified case-crossover analyses to examine the hourly association between exposure to air pollutants (particles with diameter ≤10 μm (PM₁₀), particles with diameter ≤2.5 μm (PM_2.5), ozone (O₃), and nitrogen dioxide (NO₂)) and risk of EDVs for asthma after controlling for temperature, relative humidity, public holidays and circulating levels of influenza and respiratory syncytial virus. Risk of EDVs for asthma increased within a few hours after exposure to O₃ (odds ratio [OR]: 1.170, 95% confidence interval (CI): 1.003-1.365) or NO₂ (OR: 1.359, 95%CI: 1.049-1.760). The association between O₃ exposure and risk of EDVs for asthma was stronger in boys (OR: 1.244, 95%CI: 1.025-1.511) than that in girls (OR: 1.055, 95%CI: 0.818-1.361). The association between NO₂ exposure and risk of EDVs for asthma was stronger in school-age children [OR ranged from 1.376 (95%CI: 1.044-1.813) to 3.607 (95%CI: 1.552-8.385) across different lags] than that in preschool-age children, whereas the association between PM₁₀ exposure and risk of EDVs for asthma was greater in preschool-age children [OR ranged from 1.873 (95%CI: 1.022-3.433) to 1.878 (95%CI: 1.028-3.431)] than that in school-age children. We observed an association of risk of EDVs for asthma with daytime air pollution exposure, but not with night-time air pollution exposure. This study suggests that risk of childhood asthma exacerbations increases within a few hours of air pollution exposure.

Association between heat exposure and hospitalization for diabetic ketoacidosis, hyperosmolar hyperglycemic state, and hypoglycemia in Japan

BACKGROUND

An increase in extreme heat events has been reported along with global warming. Heat exposure in ambient temperature is associated with all-cause diabetes mortality and all-cause hospitalization in diabetic patients. However, the association between heat exposure and hospitalization for hyperglycemic emergencies, such as diabetic ketoacidosis (DKA), hyperosmolar hyperglycemic state (HHS), and hypoglycemia is unclear. The objective of our study is to clarify the impact of heat exposure on the hospitalization for DKA, HHS, and hypoglycemia.

METHODS

Data of daily hospitalizations for hyperglycemic emergencies (i.e., DKA or HHS) and hypoglycemia was extracted from a nationwide administrative database in Japan and linked with temperature in each prefecture in Japan during 2012-2019. We applied distributed lag non-linear model to evaluate the non-linear and lagged effects of heat exposure on hospitalization for hyperglycemic emergencies.

RESULTS

The pooled relative risk for hyperglycemic emergencies of heat effect (the 90th percentile of temperature with reference to the 75th percentile of temperature) and extreme heat effect (the 99th percentile of temperature with reference to the 75th percentile of temperature) over 0-3 lag days was 1.27 (95 %CI: 1.16-1.39) and 1.64 (95 %CI: 1.38-1.93), respectively. The pooled relative risk for heat effect on hospitalization for hypoglycemia and extreme heat effect over 0-3 lag days was 1.33 (95 %CI: 1.17-1.52) and 1.65 (95 %CI: 1.29-2.10), respectively. These associations were consistent by type of hyperglycemic emergencies and type of diabetes and were generally consistent by regions.

DISCUSSION

Heat exposure was associated with hospitalizations for DKA, HHS and hypoglycemia. These results may be useful to guide preventive actions for the risk of fatal hyperglycemic emergencies and hypoglycemia.

Impact of low-intensity heat events on mortality and morbidity in regions with hot, humid summers: a scoping literature review

The objective of this study is to determine the impacts of low-intensity heat on human health in regions with hot, humid summers. Current literature has highlighted an increase in mortality and morbidity rates during significant heat events. While the impacts on high-intensity events are established, the impacts on low-intensity events, particularly in regions with hot, humid summers, are less clear. A scoping review was conducted searching three databases (PubMed, EMBASE, Web of Science) using key terms based on the inclusion criteria. We included papers that investigated the direct human health impacts of low-intensity heat events (single day or heatwaves) in regions with hot, humid summers in middle- and high-income countries. We excluded papers written in languages other than English. Of the 600 publications identified, 33 met the inclusion criteria. Findings suggest that low-intensity heatwaves can increase all-cause non-accidental, cardiovascular-, respiratory- and diabetes-related mortality, in regions experiencing hot, humid summers. Impacts of low-intensity heatwaves on morbidity are less clear, with research predominantly focusing on hospitalisation rates with a range of outcomes. Few studies investigating the impact of low-intensity heat events on emergency department presentations and ambulance dispatches were found. However, the data from a limited number of studies suggest that both of these outcome measures increase during low-intensity heat events. Low-intensity heat events may increase mortality. There is insufficient evidence of a causal effect of low-intensity heat events on increasing morbidity for a firm conclusion. Further research on the impact of low-intensity heat on morbidity and mortality using consistent parameters is warranted.

Exposure to heat during pregnancy and preterm birth in North Carolina: Main effect and disparities by residential greenness, urbanicity, and socioeconomic status

BACKGROUND

Although previous literature suggested that several factors may be associated with higher risk of adverse health outcomes related to heat, research is limited for birth outcomes.

OBJECTIVES

We investigated associations between exposure to heat/heat waves during the last week of gestation and preterm birth (PTB) in North Carolina (NC) and evaluated effect modification by residential greenness, urbanicity, and socioeconomic status (SES).

METHODS

We obtained individual-level NC birth certificate data for May-September 2003-2014. We estimated daily mean temperature at each maternal residential address using Parameter-elevation Regressions on Independent Slopes Model (PRISM) data. We created 3 definitions of heat waves (daily temperature ≥95th, 97th, 99th percentile for NC warm season temperature, for ≥2 consecutive days). Normalized Difference Vegetation Index (NDVI) was used to assess residential greenness. Community-level modifiers (e.g., income, urbanicity) were considered. We applied Cox proportional hazard models to estimate the association between exposure to heat/heat waves and PTB, controlling for covariates. Stratified analyses were conducted to evaluate whether the association between heat and PTB varied by several individual and community characteristics.

RESULTS

Of the 546,441 births, 8% were preterm. Heat exposure during the last week before delivery was significantly associated with risk of PTB. The hazard ratio for a 1 °C increase in temperature during the last week before delivery was 1.01 (95% CI: 1.00, 1.02). Higher heat-PTB risk was associated with some characteristics (e.g., areas that were urbanized, low SES, or in the Coastal Plain). We also found significant PTB-heat risk in areas with low greenness for urbanized area. For heat waves, we did not find significantly positive associations with PTB.

DISCUSSION

Findings provide evidence that exposure to heat during pregnancy increases risk of PTB and suggest disparities in these risks. Our results have implications for future studies of disparity in heat and birth outcomes associations.

Hourly air pollution exposure and emergency department visit for acute myocardial infarction: Vulnerable populations and susceptible time window

Although short-term exposure to air pollution can trigger sudden heart attacks, evidence is scarce regarding the relationship between sub-daily changes in air pollution level and the risk of acute myocardial infarction (AMI). Here we assessed the intraday effect of air pollution on AMI risk and potential effect modification by pre-existing cardiac risk factors. Hourly data on emergency department visits (EDVs) for AMI and air pollutants in Brisbane, Australia during 2013-2015 were acquired from pertinent government departments. A time-stratified case-crossover analysis was adopted to examine relationships of AMI risk with hourly changes in particulate matters (aerodynamic diameter ≤ 2.5 μm (PM_2.5) and ≤10 μm (PM₁₀)) and gaseous pollutants (ozone and nitrogen dioxide) after adjusting for potential confounders. We also conducted stratified analyses according to age, gender, disease history, season, and day/night time exposure. Excess risk of AMI per 10 μg/m³ increase in air pollutant concentration was reported at four time windows: within 1, 2-6, 7-12, and 13-24 h. Both single- and multi-pollutant models found an elevated risk of AMI within 2-6 h after exposure to PM_2.5 (excessive risk: 12.34%, 95% confidence interval (CI): 1.44%-24.42% in single-pollutant model) and PM₁₀ within 1 h (excessive risk: 5.21%, 95% CI: 0.26%-10.40% in single-pollutant model). We did not find modification effect by age, gender, season or day/night time, except that PM_2.5 had a greater effect on EDVs for AMI during night-time than daytime. Our findings suggest that AMI risk could increase within hours after exposure to particulate matters.

Extreme temperature exposure and acute myocardial infarction: Elevated risk within hours?

Day-to-day change in ambient temperature is associated with acute myocardial infarction (AMI) attacks, but evidence is scarce about the effects of extreme temperatures on the risk of AMI within hours of exposure. This study investigated the hour-level associations between extreme temperatures and AMI occurrence. State-wide data on AMI patients and temperature during winter and summer of 2013-2015 were obtained for Queensland state of Australia. We employed a fixed time-stratified case-crossover analysis to quantify the risk of AMI associated with temperature within 24 h after exposure. Subgroups analyses by age, gender and disease history were also conducted. We observed a very acute effect of cold on men (occurred 9-10 h after exposure), women (19-22 h after exposure), and the elderly (4-20 h after exposure). Cold was associated with elevated AMI risk for men within 9 h (OR = 2.1, 95 % CI: 1.2-3.6), women within 19 h (OR = 2.5, 95 % CI: 1.0-6.0), and the elderly within 4 h (OR: 2.0, 95 % CI: 1.0-4.0). However, elevated risk of AMI associated with heat occurred 15 h later for men (OR: 3.9; 95 % CI: 1.1-13.9) and 23 h later for adults (OR: 4.1, 95 % CI: 1.1-15.4). People never suffered AMI and the elderly with diabetes or hyperlipidaemia were particularly vulnerable to cold. Those that were particularly vulnerable to heat were men never experienced AMI or having hypertension or having hyperlipidaemia as well as women ever suffered AMI. Effects of temperature on AMI risk at sub-daily timescales should be considered to prevent cardiac events.

Associations of heat and cold with hospitalizations and post-discharge deaths due to acute myocardial infarction: what is the role of pre-existing diabetes?

BACKGROUND

The existing evidence suggests that pre-existing diabetes may modify the association between heat and hospitalizations for acute myocardial infarction (AMI).

METHODS

This study included patients who were hospitalized for AMI from 1 January 2005 to 31 December 2013 in Brisbane, Australia, and also included those who died within 2 months after discharge. A time-stratified case-crossover design with conditional logistic regression was used to quantify the associations of heat and cold with hospitalizations and post-discharge deaths due to AMI in patients with and without pre-existing diabetes. Stratified analyses were conducted to explore whether age, sex and suburb-level green space and suburb-level socio-economic status modified the temperature-AMI relationship. Heat and cold were defined as the temperature above/below which the odds of hospitalizations/deaths due to AMI started to increase significantly.

RESULTS

There were 14 991 hospitalizations for AMI and 1811 died from AMI within 2 months after discharge during the study period. Significant association between heat and hospitalizations for AMI was observed only in those with pre-existing diabetes (odds ratio: 1.19, 95% confidence interval: 1.00-1.41) [heat (26.3°C) vs minimum morbidity temperature (22.2°C)]. Cold was associated with increased odds of hospitalizations for AMI in both diabetes and non-diabetes groups. Significant association between cold and post-discharge deaths from AMI was observed in both diabetes and non-diabetes groups.

CONCLUSIONS

Individuals with diabetes are more susceptible to hospitalizations due to AMI caused by heat and cold.

Assessing the effects of non-optimal temperature on risk of gestational diabetes mellitus in a cohort of pregnant women in Guangzhou, China

Previous observational studies have shown that exposure to ambient temperature and air pollution were associated with the incidence of gestational diabetes mellitus (GDM). However, the susceptible time window of non-optimal temperature on GDM is still unknown, and the interaction with air pollution has not been examined. We conducted a prospective cohort study in Guangzhou, China to investigate the windows of susceptibility of temperature extremes and variability on the risk of GDM and to explore any interaction effect with air pollution. Daily maximum (T_max), minimum temperature (T_min) and diurnal temperature range (DTR) were obtained from Guangdong Meteorological Service. Distributed lag non-linear models with a logistic regression were applied to assess the effect of temperature extremes and DTR in different weeks of gestation on GDM. To examine the interaction effect, relative excess risk due to interaction index, attributable proportion and synergy index were calculated. There were 5,165 pregnant women enrolled, of which 604 were diagnosed with GDM (11.7%). Compared with a reference temperature (50th percentile of T_max), we found that extreme high temperature (99th percentile of T_max) exposure during 21st and 22nd gestational weeks was associated with an increased risk of GDM. Extreme low temperature (1st percentile of T_max) exposure during 14th to 17th weeks increased the risk of GDM. We observed that per 1 °C increment of DTR during 21st to 24th weeks was associated with an elevated GDM risk. No interaction effect of temperature extremes or variability with air pollution on GDM were observed. Our results suggested that non-optimal temperature is an independent risk factor of GDM. The time window of susceptibility for extreme temperatures and DTR exposure on the risk of GDM generally occurred in second trimester of pregnancy. In the context of climate change, our study has important implications for reproductive health and justifies more research in different climate zones.

Increasing impacts of temperature on hospital admissions, length of stay, and related healthcare costs in the context of climate change in Adelaide, South Australia

BACKGROUND

A growing number of studies have investigated the effect of increasing temperatures on morbidity and health service use. However, there is a lack of studies investigating the temperature-attributable cost burden.

OBJECTIVES

This study examines the relationship of daily mean temperature with hospital admissions, length of hospital stay (LoS), and costs; and estimates the baseline temperature-attributable hospital admissions, and costs and in relation to warmer climate scenarios in Adelaide, South Australia.

METHOD

A daily time series analysis using distributed lag non-linear models (DLNM) was used to explore exposure-response relationships and to estimate the aggregated burden of hospital admissions for conditions associated with temperatures (i.e. renal diseases, mental health, diabetes, ischaemic heart diseases and heat-related illnesses) as well as the associated LoS and costs, for the baseline period (2010-2015) and different future climate scenarios in Adelaide, South Australia.

RESULTS

During the six-year baseline period, the overall temperature-attributable hospital admissions, LoS, and associated costs were estimated to be 3915 cases (95% empirical confidence interval (eCI): 235, 7295), 99,766 days (95% eCI: 14,484, 168,457), and AU$159 million (95% eCI: 18.8, 269.0), respectively. A climate scenario consistent with RCP8.5 emissions, and including projected demographic change, is estimated to lead to increases in heat-attributable hospital admissions, LoS, and costs of 2.2% (95% eCI: 0.5, 3.9), 8.4% (95% eCI: 1.1, 14.3), and 7.7% (95% eCI: 0.3, 13.3), respectively by mid-century.

CONCLUSIONS

There is already a substantial temperature-attributable impact on hospital admissions, LoS, and costs which are estimated to increase due to climate change and an increasing aged population. Unless effective climate and public health interventions are put into action, the costs of treating temperature-related admissions will be high.

Using logic regression to characterize extreme heat exposures and their health associations: a time-series study of emergency department visits in Atlanta

Background

Short-term associations between extreme heat events and adverse health outcomes are well-established in epidemiologic studies. However, the use of different exposure definitions across studies has limited our understanding of extreme heat characteristics that are most important for specific health outcomes or subpopulations.

Methods

Logic regression is a statistical learning method for constructing decision trees based on Boolean combinations of binary predictors. We describe how logic regression can be utilized as a data-driven approach to identify extreme heat exposure definitions using health outcome data. We evaluated the performance of the proposed algorithm in a simulation study, as well as in a 20-year time-series analysis of extreme heat and emergency department visits for 12 outcomes in the Atlanta metropolitan area.

Results

For the Atlanta case study, our novel application of logic regression identified extreme heat exposure definitions that were associated with several heat-sensitive disease outcomes (e.g., fluid and electrolyte imbalance, renal diseases, ischemic stroke, and hypertension). Exposures were often characterized by extreme apparent minimum temperature or maximum temperature over multiple days. The simulation study also demonstrated that logic regression can successfully identify exposures of different lags and duration structures when statistical power is sufficient.

Conclusion

Logic regression is a useful tool for identifying important characteristics of extreme heat exposures for adverse health outcomes, which may help improve future heat warning systems and response plans.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-021-01278-x.

Associations of extreme temperatures with hospitalizations and post-discharge deaths for stroke: What is the role of pre-existing hyperlipidemia?

BACKGROUND

Existing evidence has suggested that heat exposure was associated with increase of low-density lipoprotein (LDL) and decrease of high-density lipoprotein (HDL). This study aimed to assess the effects of extreme temperatures (i.e., heat and cold) on hospitalizations and post-discharge deaths for stroke amongst individuals with and without pre-existing hyperlipidemia, and examine whether individual- and community-level characteristics modified the temperature-stroke relationship.

METHODS

People who were hospitalized for stroke from 1^st January 2005 to 31^st December 2013 in Brisbane, Australia, and died from stroke within two months after discharge were included in this cohort study. The effects of extreme temperatures on hospitalizations and post-discharge deaths for stroke in patients with and without pre-existing hyperlipidemia were quantified using a time-stratified case-crossover design with conditional logistic regression. Suburb-level temperature data were used to minimize exposure measurement bias. Relative humidity, NO₂ and PM₁₀ were adjusted as potential confounders in the regression. Subgroup analyses were conducted to examine if age, sex, and suburb-level greenspace (measured as normalized difference vegetation index (NDVI)) and socioeconomic status (measured as Socio-Economic Indexes for Areas (SEIFA)) modified the temperature-stroke relationship in the hyperlipidemia group and the non-hyperlipidemia group.

RESULTS

There were 11,469 hospitalizations for stroke during the study period, and 2270 (19.79%) of them died within two months after discharge. Significant effect of heat on hospitalizations for stroke was observed only in individuals with pre-existing hyperlipidemia (odds ratio (OR): 1.85; 95% confidence interval (CI): 1.07-3.19), and significant effect of cold on hospitalizations was found in individuals without pre-existing hyperlipidemia (OR: 1.60; 95% CI: 1.03-2.47). Males appeared to be more vulnerable to the effects of heat and cold on hospitalizations for stroke than females. People living in suburbs with low-level greenspace (OR: 4.23; 95% CI: 1.08-16.61) were more vulnerable to heat effect on stroke hospitalizations than those living in suburbs with high-level greenspace (OR: 1.41; 95% CI: 0.32-6.16). People living in suburbs with the lowest socioeconomic advantage level or the lowest economic resources level were most vulnerable the effects of heat and cold on hospitalizations for stroke. No significant effect of heat or cold on post-discharge deaths from stroke was observed.

CONCLUSIONS

This study provides suggestive evidence that heat adaptation strategies aiming to reduce stroke attacks may need to target those individuals with pre-existing hyperlipidemia.

Intraday effects of outdoor air pollution on acute upper and lower respiratory infections in Australian children

Children's respiratory health are particularly vulnerable to outdoor air pollution, but evidence is lacking on the very acute effects of air pollution on the risk of acute upper respiratory infections (AURI) and acute lower respiratory infections (ALRI) in children. This study aimed to evaluate the risk of cause-specific AURI and ALRI, in children within 24 h of exposure to air pollution. We obtained data on emergency cases, including 11,091 AURI cases (acute pharyngitis, acute tonsillitis, acute obstructive laryngitis and epiglottitis, and unspecified acute upper respiratory infections) and 11,401 ALRI cases (pneumonia, acute bronchitis, acute bronchiolitis, unspecified acute lower respiratory infection) in Brisbane, Australia, 2013-2015. A time-stratified case-crossover analysis was used to examine the hourly association of AURI and ALRI with high concentration (95th percentile) of four air pollutants (particulate matters with aerodynamic diameter <10 μm (PM₁₀) and <2.5 μm (PM_2.5), ozone (O₃), nitrogen dioxide (NO₂)). We observed increased risk of acute tonsillitis associated with PM_2.5 within 13-24 h (odds ratio (OR), 1.45; 95% confidence interval [CI], 1.02-2.06) and increased risk of unspecified acute upper respiratory infections related to O₃ within 2-6 h (OR, 1.38, 95%CI, 1.12-1.70), NO₂ within 1 h (OR, 1.19; 95%CI, 1.01-1.40), and PM_2.5 within 7-12 h (OR, 1.21; 95%CI, 1.02-1.43). Cold season and nigh-time air pollution has greater effects on AURI, whereas greater risk of ALRI was seen in warm season and daytime. Our findings suggest exposures to particulate and gaseous air pollution may transiently increase risk of AURI and ALRI in children within 24 h. Prevention measures aimed at protecting children's respiratory health should consider the very acute effects of air pollution.

Impacts of urbanization on the temperature-cardiovascular mortality relationship in Beijing, China

The effect of temperature on cardiovascular disease (CVD) mortality has been extensively studied. However, it remains largely unknown over whether there is any difference between urban and suburban areas within the same city and how urbanization modifies the relationship between temperature and CVD mortality. In order to examine whether the association between temperature and CVD mortality existed difference in urban and suburban areas, and how urbanization modified this association, we used a distributed lag nonlinear model and a generalized additive model to investigate temperature-related CVD mortality in urban and suburban areas in Beijing, China, from 2006 to 2011. The age, gender, and educational attainment of the population were stratified to explore the modifying effect. We observed that the impacts of heat and cold temperature on CVD mortality were higher in suburban areas than in urban areas. In addition, the elderly and illiterate subjects in suburban areas were more vulnerable to both heat and cold than their counterparts in urban areas. Moreover, higher urbanization levels were significantly associated with districts having lower the excess risks for temperature- CVD mortality. Our findings provide evidence that populations in suburban Beijing have higher risk of temperature-related CVD mortality than those in urban areas. Therefore, greater attention should be paid to vulnerable groups in suburban areas to reduce temperature-related health burden.

A systematic review considering risk factors for mortality of patients discharged from hospital with a diagnosis of diabetes

AIM

To identify known risk factors for mortality for adult patients, discharged from hospital with diabetes.

METHOD

The systematic review was based on the PRISMA protocol. Studies were identified through EMBASE & MEDLINE databases. The inclusion criteria were papers that were published over the last 6 years, in English language, and focused on risk factors of mortality in adult patients with diabetes, after they were discharged from hospitals. This was followed by data extraction "with quality assessment and semi-quantitative synthesis according to PRISMA guidelines".

RESULTS

There were 35 studies identified, considering risk factors relating to mortality for patients, discharged from hospital with diabetes. These studies are distributed internationally. 48 distinct statistically significant risk factors for mortality can be identified. Risk factors can be grouped into the following categories; demographic, socioeconomic, lifestyle, patient medical, inpatient stay, medication related, laboratory results, and gylcaemic status. These risk factors can be further divided into risk factors identified in generalized populations of patients with diabetes, compared to specific sub-populations of people with diabetes.

CONCLUSION

A relatively small number of studies have considered risk factors relating to mortality for patients, discharged from hospital with a diagnosis of diabetes. Mortality is an important outcome, when considering discharge from hospital with diabetes. However, there has only been limited consideration within the research literature.

Defining heat waves and extreme heat events using sub-regional meteorological data to maximize benefits of early warning systems to population health

BACKGROUND

Extreme heat events have been consistently associated with an increased risk of hospitalization for various hospital diagnoses. Classifying heat events is particularly relevant for identifying the criteria to activate early warning systems. Heat event classifications may also differ due to heterogeneity in climates among different geographic regions, which may occur at a small scale. Using local meteorological data, we identified heat waves and extreme heat events that were associated with the highest burden of excess hospitalizations within the County of San Diego and quantified discrepancies using county-level meteorological criteria.

METHODS

Eighteen event classifications were created using various combinations of temperature metric, percentile, and duration for both county-level and climate zone level meteorological data within San Diego County. Propensity score matching and Poisson regressions were utilized to ascertain the association between heat wave exposure and risk of hospitalization for heat-related illness and dehydration for the 1999-2013 period. We estimated both relative and absolute risks for each heat event classification in order to identify optimal definitions of heat waves and extreme heat events for the whole city and in each climate zone to target health impacts.

RESULTS

Heat-related illness differs vastly by level (county or zone-specific), definition, and risk measure. We found the county-level definitions to be systematically biased when compared to climate zone definitions with the largest discrepancy of 56 attributable hospitalizations. The relative and attributable risks were often minimally correlated, which exemplified that relative risks alone are not adequate to optimize heat waves definitions.

CONCLUSIONS

Definitions based on county-level defined thresholds do not provide an accurate picture of the observed health effects and will fail to maximize the potential effectiveness of heat warning systems. Absolute rather than relative risks are a more appropriate measure to define the set of criteria to activate early warnings systems and thus maximize public health benefits.

Geographical disparities in the impacts of heat on diabetes mortality and the protective role of greenness in Thailand: A nationwide case-crossover analysis

Diabetes is a major public health problem globally, and heat exposure may be a potential risk factor for death among diabetes. This study examines the association between heat and diabetes mortality in different regions of Thailand and investigates whether heat effects are modified by regional greenness. Daily temperature and daily diabetes deaths data were obtained for 60 provinces of Thailand during 2000-2008. A case-crossover analysis was conducted to quantify the odds of heat-related death among diabetes. Meta-regression was then used to examine potential modification effects of regional greenness (as represented by the Normalized Difference Vegetation Index) on heat-related mortality. A strong association between heat and diabetes mortality was found in Thailand, with important regional variations. Nationally, the pooled odds ratio of diabetes mortality was 1.10 (95% confidence interval (CI): 1.06-1.14) for heat (90th percentile of temperature) and 1.20 (95% CI: 1.10-1.30) for extreme heat (99th percentile of temperature) compared with the minimum mortality temperature, across lag 0-1 days. Central and northeast Thailand were the most vulnerable regions. Regional greenness modified the effects of heat, with lower mortality impacts in areas of higher levels of greenness. In conclusion, heat exposure increases mortality risk in diabetes, with large geographical variations in risk suggesting the need for region-specific public health strategies. Increasing greenness levels may help to reduce the burden of heat on diabetes in Thailand against the backdrop of a warming climate.

Heat and risk of acute kidney injury: An hourly-level case-crossover study in queensland, Australia

BACKGROUND

The effects of hourly differences in temperature on the risk of acute kidney injury have not been investigated so far. This study aimed to examine a very short-term effect of heat on the risk of acute kidney injury at an hourly level and assessed potential modification effects by age, gender and preexisting diseases.

METHODS

We performed a time-stratified case-crossover design with a conditional logistic regression model to examine the association between hourly temperature and hourly emergency department visits for acute kidney injury (N = 1815) in Queensland state of Australia, 2013-2015. Heat effect on acute kidney injury was reported for temperature increases from 50th percentile (26.1 °C) to 95th percentile (33.6 °C).

RESULTS

The effect of heat on acute kidney injury occurred in the same hour of heat exposure (odds ratio (OR): 1.37; 95% confidence interval (CI): 1.10, 1.71), with no temperature threshold observed. Males (OR: 2.48; 95% CI: 1.85, 3.32) and those aged >64 years (OR: 2.93; 95% CI: 2.01, 4.27), particularly those with pre-existing diabetes (OR: 2.51; 95% CI: 1.91, 3.30), hypertension (OR: 2.25; 95% CI: 1.61, 3.15), heart failure (OR: 2.21; 95% CI: 1.72, 2.84), or chronic kidney disease (OR: 2.59; 95% CI: 1.89, 3.55), were at great risks of acute kidney injury attack after exposure to heat.

CONCLUSIONS

General practitioners and specialists should remind their patients about this risk in summer. Tailored heat adaptation strategies protecting adults working outdoors are urgently needed, especially within the context of climate change.