Case-crossover Analysis Research Articles

Landscape fire smoke enhances the association between fine particulate matter exposure and acute respiratory infection among children under 5 years of age: Findings of a case-crossover study for 48 low- and middle-income countries

BackgroundFine particulate matter (PM2.5) produced by landscape fires is thought to be more toxic than that from non-fire sources. However, the effects of “fire-sourced” PM2.5 on acute respiratory infection (ARI) are unknown. MethodsWe combined Demographic and Health Survey (DHS) data from 48 countries with gridded global estimates of PM2.5 concentrations from 2003 to 2014. The proportions of fire-sourced PM2.5 were assessed by a chemical transport model using a variety of PM2.5 source data. We tested for associations between ARI and short-term exposure to fire- and “non-fire-sourced” PM2.5 using a bidirectional case-crossover analysis. The robustness and homogeneity of the associations were examined by sensitivity analyses. We also established a nonlinear exposure–response relationship between fire- and non-fire-sourced PM2.5 and ARI using a two-dimensional spline function. ResultsThe study included 36,432 children under 5 years who reported ARI symptoms. Each 1 µg/m3 increment of fire-sourced PM2.5 was associated with a 3.2 % (95 % confidence interval [CI] 0.2, 6.2) increment in the risk of ARI. This effect was comparable to that of each ∼5 µg/m3 increment in PM2.5 from non-fire sources (3.1 %; 95 % CI 2.4, 3.7). The association between ARI and total PM2.5 concentration was significantly mediated by the proportion of fire-sourced particles. Nonlinear analysis showed that the risk of ARI was increased by both fire- and non-fire-sourced PM2.5, but especially by the former. ConclusionsPM2.5 produced by landscape fire was more strongly associated to ARI among children under 5 years than that from non-fire sources.

Ambient heat stress and urolithiasis attacks in China: Implication for climate change

BackgroundAlthough the existing studies have suggested a significant association between high temperatures and urolithiasis, no nationwide studies have quantified the burden attributable to environmental heat stress and explored how the urolithiasis burden would vary in a warming climate. MethodsWe collected data on urolithiasis attacks from 137 hospitals in 59 main cities from 20 provincial regions of China from 2000 to 2020. An individual-level case-crossover analysis was conducted to estimate the effect of daily wet-bulb globe temperature (WBGT), a heat stress index combining temperature and humidity, on urolithiasis attacks. Stratified analyses were performed by region, age, and sex. We further quantified the future WBGT-related burden of urolithiasis from the Coupled Model Intercomparison Project Phase 6 under three Shared Socioeconomic Pathway (SSP) scenarios. ResultsIn total, 118,180 urolithiasis patients were evaluated. The exposure-response curve for the association between WBGT and urolithiasis attacks was J-shaped, with a significantly increased risk for WBGT higher than 14.8 °C. The middle-aged and elderly group (≥45 years old) had a higher risk of WBGT-related urolithiasis attacks than in the younger group, while no significant sex difference was observed. The attributable fraction (AF) due to high WBGT would increase from 10.1% in the 2010s to 16.1% in the 2090s under the SSP585 scenario. Warm regions were projected to experience disproportionately higher AFs and larger increments in the future. ConclusionsThis nationwide investigation provides novel evidence on the acute effect of high WBGT on urolithiasis attacks and demonstrates the increasing disease burden in a warming climate.

Short-term effects of PM1, PM2.5, and PM2.5 constituents on myocardial infarction mortality in qingdao, China: A time-stratified case-crossover analysis

Myocardial infarction (MI) is a major global contributor to disability and death. Few studies have investigated the impacts of short-term exposure to particulate matter with an aerodynamic diameter ≤1 μm (PM1) and ≤2.5 μm (PM2.5) constituents on MI mortality. We aimed to estimate the risks of MI mortality related to short-term exposures to PM1, PM2.5, and PM2.5 constituents. Daily MI deaths, daily concentrations of PM1, PM2.5, PM2.5 chemical compositions, and meteorological data in Qingdao during 2015–2019 were collected. We used a time-stratified case-crossover design fitted with a conditional quasi-Poisson regression incorporated with distributed lag model to quantify the associations between PM1, PM2.5, and PM2.5 chemical compositions and MI mortality. Subgroup analyses were further implemented based on sex, age, and season. There were 36,235 MI deaths in Qingdao during 2015–2019. The results of single-day lagged effects showed that PM1 (lag0 and lag1 days), PM2.5 (lag0 and lag1 days), sulfate (lag0 and lag1 days), nitrate (lag0 day), ammonium (lag0 and lag1 days), and black carbon (BC, lag0 and lag1 days) were positively related to an elevated risk of MI death. The cumulative effects of per interquartile range (IQR) rise in PM1, PM2.5, sulfate, nitrate, ammonium, and BC concentrations lasting for three days (lag02 day) were related to excess risks of 2.5% (95% confidence interval [CI]: 0.2%, 4.9%), 2.0% (0.1%, 3.9%), 2.2% (0.3%, 4.1%), 2.0% (0.1%, 3.9%), 2.0% (0.1%, 4.0%), and 2.1% (0.2%, 3.9%) for MI mortality, respectively. Significant effects of PM1, PM2.5, sulfate, and BC exposures on excess risks of MI mortality were observed in aging subpopulations or during the cold season. Short-term exposures to PM1, PM2.5, sulfate, nitrate, ammonium, and BC were linked to elevated risks of MI mortality. These results strengthen the case for implementing policies to reduce air pollution.

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.

Association between Short-Term Exposure to Air Pollution and COVID-19 Mortality: A Population-Based Case-Crossover Study Using Individual-Level Mortality Registry Confirmed by Medical Examiners.

Studies have suggested links between ambient air pollution and coronavirus 2019 (COVID-19) mortality, yet confirmation by well-designed epidemiological studies with individual data is needed. We aimed to examine whether short-term exposure to air pollution is associated with risk of mortality from COVID-19 for those infected with COVID-19. The Cook County Medical Examiner's Office reports individual-level data for deaths from COVID-19 that occur in its jurisdiction, which includes all confirmed COVID-19 deaths in Cook County, Illinois. Case-crossover analysis was conducted to estimate the associations of estimated short-term exposures to particulate matter (PM) with aerodynamic diameter () and ozone () on the day of death and up to 21 d before death at location of death with COVID-19. A total of 7,462 deaths from COVID-19 that occurred up to 28 February 2021 were included in the final analysis. We adjusted for potential confounders by time-stratified case-crossover design and by covariate adjustments (i.e., time-invariant factors, meteorological factors, viral transmission, seasonality, and time trend). Of the 7,462 case and 25,457 self-control days, almost all were days with exposure levels below the 24-h National Ambient Air Quality Standard (NAAQS) (); 98.9% had levels below the maximum 8-h NAAQS ( or 70 parts per billion). An interquartile range (IQR) increase () in cumulative 3-wk exposure was associated with a 69.6% [95% confidence interval (CI): 34.6, 113.8] increase in risk of COVID-19 mortality. An IQR increase () in 3-d exposure was associated with a 29.0% (95% CI: 9.9, 51.5) increase in risk of COVID-19 mortality. The associations differed by demographics or race/ethnicity. There was indication of modification of the associations by some comorbid conditions. Short-term exposure to air pollution below the NAAQS may increase the mortality burden from COVID-19. https://doi.org/10.1289/EHP10836.

Short-term effect of air pollution on childhood epilepsy in eastern China: A space–time-stratified case-crossover and pooled analysis

BackgroundGrowing studies suggest that air pollution exposure is an emerging driver for neurological diseases, but existing evidence on the association between air pollution and epilepsy is scarce. Here, we aimed to quantitatively estimated the short-term effects of various air pollutants on childhood epilepsy hospitalizations in China. MethodsWe obtained daily electronic health records on childhood epilepsy hospitalizations and air pollutants (PM2.5, PM10-2.5, PM10, SO2, NO2, O3) from 2016 through 2018 in 10 cities of Anhui Province in China. In the first stage, a space–time-stratified case-crossover analysis was employed to evaluate the short-term association of childhood epilepsy hospitalizations with each air pollutant in Anhui Province. In the second stage, short-term effect of air pollution on childhood epilepsy morbidity reported in Anhui Province and in previous studies was pooled with a random-effect meta-analysis model to get the overall effect of different air pollutants in eastern China. ResultsThis study included 8,181 childhood epilepsy patients from 10 cities in Anhui province of China. The first stage case-crossover analysis in Anhui province found significant associations between higher concentrations of all air pollutants (except O3) and increased risk of childhood epilepsy hospitalizations. Each 10 μg/m3 increase in PM2.5, PM10-2.5, PM10, SO2, and NO2 concentrations was associated with an increase of 1.1 % [95 % confidence interval (CI): 0.1 %-2.1 %], 1.7 % (95 %CI: 0.5 %-2.9 %), 0.8 % (95 %CI: 0.1 %-1.4 %), 8.5 % (95 %CI: 1.5 %-16.0 %), and 4.3 % (95 %CI: 2.3 %-6.3 %) in epilepsy hospitalizations, respectively. We also observed greater effects of particulate matter in cold season. The second stage meta-analysis that additionally included two prior studies with 43,002 patients from other 11 cities found a marginally significant increase in childhood epilepsy attacks associated with PM2.5, PM10, and NO2 in eastern China. ConclusionsShort-term exposure to both particulate matter and gaseous air pollution was associated with an increased risk of childhood epilepsy exacerbation in eastern China. Our findings suggest that air pollution exposure especially in cold season needs to be considered by children’s parents or guardians to prevent epilepsy attacks.

Comparison of time series and case-crossover analyses in environmental epidemiology

Time-series and case-crossover are two main study designs in environmental epidemiology. However, due to the differences in design principles and model construction between the two analyses, the results of the two analyses may not be consistent. Herein, we examined the short-term effect of cold spells on cardiovascular mortality in Nanjing using both time series and case-crossover analyses, aiming to provide a basis for the selection of appropriate research design in environmental epidemiology.

Association between short-term exposure to extreme humidity and painful diabetic neuropathy: a case-crossover analysis.

Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus, which reduces the quality of life. However, the association between PDN and environmental factors, especially ambient humidity, remains unclear. Therefore, this study investigated the impact of extreme humidity events on PDN. Data on PDN-related hospital admissions to two tertiary hospitals in Hefei, China (2014-2019) were obtained. A distributed lag non-linear model with a case-crossover design was used to quantitatively estimate the effects of ambient humidity on PDN, and the results were stratified by sex and age. The 1st, 10th, 90th, and 99th percentiles of relative humidity (RHU) were defined as extreme humidity, and the average relative humidity (74.94%) was set as the reference value. Non-linear exposure-response curves between the RHU and PDN cases were obtained. Extreme humidity (92%) had a significant effect on PDN with a relative risk (RR) of 1.13 (95% confidence interval (CI): 1.01-1.26) on a particular day, which increased with the RHU (RR: 1.21, 95% CI: 1.02-1.45 at 98% extreme humidity). Stratification analysis showed that women (RR: 1.38, 95% CI: 1.07-1.77) and patients aged < 65years (RR: 1.26, 95% CI: 1.01-1.57) were highly susceptible to this effect on the same day. The results suggest that extreme humidity is a crucial trigger for PDN onset in diabetes patients. Furthermore, the effects vary with sex and age. This study provides detailed evidence of the adverse effects of extreme weather on diabetes patients.

Discussion on "A formal causal interpretation of the case-crossover design" by Zach Shahn, Miguel A. Hernán, and James M. Robins.

It has always been clear that the case-crossover design works, for some definition of "works," but some of the details have been surprisingly elusive, and it is good to see more of them nailed down by Shahn etal. My interest in case-crossover analyses has mostly been in the context of air pollution epidemiology mentioned at the end of the paper. The air pollution setting is distinctive for several reasons: as the exposure variable is plausibly exogenous, it is possible to use control times after the case time, the effects of interest are quite small, and the same measured exposure series is shared over many-perhaps all-of the cohort.

Discussion of "A formal causal interpretation of the case-crossover design" by Zach Shahn, Miguel A. Hernan, and James M. Robins.

Shahn, Hernan, and Robins give conditions under which estimates from a case-crossover analysis converge to the desired causal relative risk times a bias factor, and they discuss conditions needed to have small bias. To simplify the problem, we discuss only two exposure times and rely on randomized exposure assignments, thereby avoiding the need for potential outcome notation. We identify many, but not all, of the conditions discussed by Shahn etal. in this simple analysis.

Association of acute ambient temperatures with NICU admissions: results of a case-crossover analysis

Background: In the face of a changing climate, understanding the impacts of increasing temperatures on population health is critical, particularly for vulnerable groups such as pregnant people and neonates. Air pollution has been shown to increase risk for neonatal intensive care unit (NICU) admission, but the effect of temperature has not been studied. Methods: Using data from the Consortium on Safe Labor (n=27,189 infants admitted to NICU), we conducted a case-crossover analysis to assess NICU admission risk in association with ambient temperature during the week prior to delivery. Hazard ratios and 95% confidence intervals estimated NICU risk associated with a 1&amp;#xb0;C increase and 1&amp;#xb0;C decrease in temperatures in the warm and cold seasons, respectively with adjustment for time-varying air pollution and humidity. Analyses were repeated among infants born during weeks with average temperatures greater than 27&amp;#xb0;C. Results: Increased temperatures in the warm season were associated with higher risk of NICU admissions on the day of delivery, the day before delivery, and the entire week while days 2-7 prior to delivery were associated with reduced risk. During the cold seasons, decreases in temperature increased risk on the day of delivery but reduced risk at other times. NICU admission risk was highest in weeks with an average temperature exceeding 27&amp;#xb0;C with 12-38% increases observed in the week preceding delivery. Conclusions: Ambient temperature, particularly increasing heat during the warm season in the week prior to delivery, was associated with NICU admission and the effects appear independent of air pollution exposures. Keywords: NICU admissions, temperature, case-crossover, neonatal health

Fetal and infant death associated with short-term ozone exposure

Background: Air pollution is linked to adverse pregnancy outcomes such as preterm births, but few studies evaluated its acute impact on fetal and infant mortality. We evaluated short-term impacts of warm-season ozone and cold-season fine particulate matter &amp;#x3c;2.5 microns (PM2.5) exposures on the risk of fetal death (&amp;#x3e;20 weeks) and infant mortality (live birth to one year). Methods: This time-stratified case-crossover analysis includes 1,880 singleton fetal deaths (2007-2011) and 3,229 singleton infant deaths (2007-2015) from the San Joaquin Valley (SJV), California. Daily ozone and PM2.5 were estimated by the SJV Air Pollution Control District and geospatially linked to maternal zip code at birth. Critical exposure windows of interest included the day of death (lag 0) up to 14 days before (lag 14). Conditional logistic regression models estimated the odds ratio (OR) and 95% confidence intervals (CI) for each 5 units increase in pollutant. Results: In warm season (May-October), a 5-ppb increase in ozone was associated with a 7% (95% CI: 2%-13%) increased risk of fetal death and 6% (95% CI: 2%-10%) increased risk of infant death within two weeks. The estimates were generally consistent from lag 0 to lag 14 for both mortality outcomes, with evidence of slightly stronger estimates for fetal death compared to infant death during certain lags. During lag 7, a 5-ppb increase in ozone was associated with a 9% increased risk in fetal death (95% CI: 5%-14%) and a 4% (95% CI: 1%-7%) increased risk in infant death. No associations were observed for cold-season PM2.5. Conclusions: Ozone exposure is positively associated with short-term risk of fetal and infant mortality in the warm season. Given the ubiquitous nature of air pollution, these associations merit further investigation. Meanwhile, efforts to minimize exposures among pregnant women may be warranted. Keywords: pollution, infant mortality, fetal death, stillbirth, pregnancy, mortality, ozone

Projections of temperature-attributable suicide under climate change scenarios in Japan

BACKGROUND AND AIM: Recent studies have projected all-cause mortality attributable to non-optimal temperature under climate change scenarios. However, the impact of climate change on mental health remains to be assessed. The short-term association between suicide and temperature has been reported, but there is a lack of future projections of temperature-attributable suicide. We projected the excess temperature-related suicide mortality in Japan under three climate change scenarios until the 2090s. METHODS: Daily time series of mean temperature and the number of suicide deaths in 1973-2015 were collected for 47 prefectures in Japan. A two-stage time-stratified case-crossover analysis was used to estimate the temperature-suicide association. We obtained the modeled daily temperature series using five general circulation models (GCMs) under three climate change scenarios from the latest Coupled Model Intercomparison Project Phase 6 (CMIP6) Shared Socioeconomic Pathways scenarios (SSPs): SSP1-2.6, SSP2-4.5, and SSP5-8.5. We projected the excess temperature-related suicide mortality until 2099 for each scenario and evaluated the net relative changes compared with the 2010s. RESULTS: During 1973-2015, there was a total of 1,049,592 suicides in Japan. Net increases in temperature-related excess suicide mortality were estimated under all scenarios, with the highest increase under the high-emission scenario (SSP5-8.5). The net change in 2090-99 compared with 2010-19 was 0.6% (95% empirical confidence interval [eCI]: 0.1, 1.6) for a low emission scenario (SSP1-2.6), 1.3% (95% eCI: 0.6, 2.4) for an intermediate scenario (SSP2-4.5), and 2.4% (95% eCI: 0.7, 3.9) for a high emission scenario (SSP5-8.5). The increases were greater the higher the emission scenarios were. The increase in excess temperature-related suicide mortality was minimized under the SSP1-2.6 scenario assuming mitigation strategies. CONCLUSIONS: The comparison of projection results under different scenarios underscores the importance of mitigation, with the higher the emissions, the greater impact on the temperature-related suicide mortality. Keywords:Climate change, non-optimal temperature, mental health, projections, DLNM

Geomagnetic Disturbances and Ventricular Arrhythmia in Patients with Implantable Cardioverter Defibrillators from a US-Based Hospital

Background and Aim: Episodes of ventricular arrhythmias (VA) have been associated with environmental exposures such as air pollution. Solar driven geomagnetic disturbances may alter autonomic nervous system activity, modify systemic oxidative stress, or induce changes in aerosols. However, few studies have investigated if there is an association between VA and geomagnetic disturbances (GMD). The aim of this study was to assess whether GMD is associated with the initiation of VA in patients with implantable cardioverter defibrillators (ICDs). Methods: This study examined the association between GMD driven by solar activity on VA, defined as sustained and non-sustained ventricular fibrillation or ventricular tachycardia, in patients with ICDs using a time-stratified case-crossover analysis between September 2006 and March 2010 from Tufts Medical Center’s Cardiac Arrythmia Center in Boston, MA. Patients were identified from a single Massachusetts-based Medical Center and VAs were identified from retrieved ICD records as part of routine care. We considered several pollutants such as PM2.5, black carbon (BC), O3, NO2 and ultrafine particles (PN) in our analyses using time lags prior to the event. Daily GMD information was appended for the week previous to each event and matched control day. Results: During the study period, 91 patients had a total of 1,050 VA. During periods of increased GMD, patients with low ejection fraction and a history of a MI or coronary intervention had increased odds of VA , with patients who had a coronary bypass graph being the highest (OR: 1.63, 95% CI 1.05, 2.52 ). Conclusions: Among patients with ICDs, exposure to GMD was associated with higher odds of VA in those with pre-existing heart disease and/or a history of coronary interventions. GMD driven by solar activity has the potential to affect heart health in patients with cardiac comorbidities. Keywords: Solar activity, geomagnetic disturbances, implantable cardioverter defibrillator, ventricular arrhythmia

Exploring the association between precipitation and mental health hospitalizations in Switzerland

Background and aim: While several studies proved the relationship between temperature and mental health, limited evidence exists on the effect of other weather factors, such as precipitation. The aim of this study was to assess the impact of precipitation on mental disorders in Switzerland between 2009–2019. Methods: Daily hospitalizations between 2009–2019 were obtained from Switzerland’s Federal Office of Statistics. Daily precipitation was taken from 2km gridded maps developed by MeteoSwiss. We conducted aggregated case-crossover analysis with a conditional quasi-Poisson regression to assess the association up to 7 days after the exposure. We considered daily precipitation in millimeters (mm), and persistent extreme precipitation events (PEP90.2) when daily precipitation exceeded the 90th percentile for more than 2 days. The analysis was conducted separately in eight Swiss main cities (Basel, Bern, Geneva, Lausanne, Lugano, Luzern, St. Gallen, and Zurich) and stratified by sex, age (&amp;#x3c;65years, &amp;#x2265;65years), and group of diagnosis (ICD-10). Models were adjusted by daily mean temperature. Results: The total number of hospital admissions included in the study was 147,768. On average, the risk of hospitalization increased by 38% (95%CI:1.30-1.46) for every 10mm increase in daily precipitation and by 52% (95%CI:1.33-1.74) for PEP90.2 events. Larger risks were found in males (1.67;95%CI:1.42-1.96, vs 1.38; 95%CI:1.17-1.63 in females) and under 65 years old (1.53;95CI:1.33-1.77 vs 1.45;95%CI:1.17-1.80 in &amp;#x2265;65years) for PEP90.2 events. By sub-diagnosis categories, larger risks were found for adult personality disorders (F60-F69) in daily precipitation (1.61;95%CI:1.42-1.83) and PEP90.2 (1.94;95%CI:1.34-2.80), while no evidence was found for developmental disorders (F80-F98) and similar risks to the average in the remaining groups. We observed a positive association in all cities with higher risks in Luzern for daily precipitation (1.68; 95%CI:1.43-1.97) and PEP90.2 (2.22; 95%CI:1.33-3.69). Conclusions: Our findings suggest that extreme precipitation events could have adverse impacts on mental health in Switzerland. Keywords: Precipitation; Climate change; Mental health

Tuberculosis Diagnoses Following Wildfire Smoke Exposure in California.

Rationale: Wildfires are a significant cause of exposure to ambient air pollution in the United States and other settings. Although indoor air pollution is a known contributor to tuberculosis reactivation and progression, it is unclear whether ambient pollution exposures, including wildfire smoke, similarly increase risk. Objectives: To determine whether tuberculosis diagnosis was associated with recent exposure to acute outdoor air pollution events, including those caused by wildfire smoke. Methods: We conducted a case-crossover analysis of 6,238 patients aged ⩾15 years diagnosed with active tuberculosis disease between 2014 and 2019 in 8 California counties. Using geocoded address data, we characterized individuals' daily exposure to <2.5 μm-diameter particulate matter (PM2.5) during counterfactual risk periods 3-6 months before tuberculosis diagnosis (hazard period) and the same time 1 year previously (control period). We compared the frequency of residential PM2.5 exposures exceeding 35 μg/m3 (PM2.5 events) overall and for wildfire-associated and nonwildfire events during individuals' hazard and control periods. Measurements and Main Results: In total, 3,139 patients experienced 1 or more PM2.5 events during the hazard period, including 671 experiencing 1 or more wildfire-associated events. Adjusted odds of tuberculosis diagnosis increased by 5% (95% confidence interval, 3-6%) with each PM2.5 event experienced over the 6-month observation period. Each wildfire-associated PM2.5 event was associated with 23% (19-28%) higher odds of tuberculosis diagnosis in this time window, whereas no association was apparent for nonwildfire-associated events. Conclusions: Residential exposure to wildfire-associated ambient air pollution is associated with an increased risk of active tuberculosis diagnosis.

Mortality Associated with Extreme Heat in Washington State: The Historical and Projected Public Health Burden

Extreme heat is one of the most important pathways illustrating the connection between climate and human health, and climate change is expected to exacerbate this public health issue. This study first used a case-crossover analysis to characterize the historical (1980–2018) association between summertime heat and non-traumatic mortality in Washington State. A separate analysis was conducted for each of the state’s ten climate divisions to produce distinct exposure–response curves expressing odds of mortality as a function of humidex. Stratified analyses were used to assess the impact of age, sex, race/ethnicity, and select causes of death, and the reported results are pooled across all divisions using meta-analysis. The historical heat–mortality relationship was combined with climate projections to estimate the impact of climate change on heat-related deaths in 2030, 2050, and 2080 under two warming scenarios. The odds ratio (OR) and 95% confidence intervals of mortality at the 99th percentile of humidex compared to the 50th percentile did not include the null value in four climate divisions (E Olympic Cascade Foothills, NE Olympic San Juan, Northeastern, and Puget Sound Lowlands). The statewide odds of mortality are 8% higher (6%, 10%) on 99th percentile days compared to 50th percentile days, driven primarily by an OR of 1.09 (1.06, 1.11) in the Puget Sound Lowlands. Risk is higher for women than men and for Blacks than Whites. Risk increases with age and for diabetic, circulatory, cardiovascular, ischemic, cerebrovascular, and respiratory deaths. The 95% confidence intervals of projected heat-attributable mortality did not overlap with zero in three climate divisions (E Olympic Cascade Foothills, NE Olympic San Juan, and Puget Sound Lowlands). In these three divisions, the average percent increase in heat-attributable mortality across both warming scenarios is 35%, 35%, and 603% in 2030, 2050, and 2080, respectively. This research is the most extensive study of heat-related mortality in Washington to date and can help inform public health initiatives aiming to improve present and future health outcomes in the state.

Antibiotic Prophylaxis Against Infective Endocarditis Before Invasive Dental Procedures

BackgroundAntibiotic prophylaxis (AP) before invasive dental procedures (IDPs) is recommended to prevent infective endocarditis (IE) in those at high IE risk, but there are sparse data supporting a link between IDPs and IE or AP efficacy in IE prevention. ObjectivesThe purpose of this study was to investigate any association between IDPs and IE, and the effectiveness of AP in reducing this. MethodsWe performed a case-crossover analysis and cohort study of the association between IDPs and IE, and AP efficacy, in 7,951,972 U.S. subjects with employer-provided Commercial/Medicare-Supplemental coverage. ResultsTime course studies showed that IE was most likely to occur within 4 weeks of an IDP. For those at high IE risk, case-crossover analysis demonstrated a significant temporal association between IE and IDPs in the preceding 4 weeks (OR: 2.00; 95% CI: 1.59-2.52; P = 0.002). This relationship was strongest for dental extractions (OR: 11.08; 95% CI: 7.34-16.74; P < 0.0001) and oral-surgical procedures (OR: 50.77; 95% CI: 20.79-123.98; P < 0.0001). AP was associated with a significant reduction in IE incidence following IDP (OR: 0.49; 95% CI: 0.29-0.85; P = 0.01). The cohort study confirmed the associations between IE and extractions or oral surgical procedures in those at high IE risk and the effect of AP in reducing these associations (extractions: OR: 0.13; 95% CI: 0.03-0.34; P < 0.0001; oral surgical procedures: OR: 0.09; 95% CI: 0.01-0.35; P = 0.002). ConclusionsWe demonstrated a significant temporal association between IDPs (particularly extractions and oral-surgical procedures) and subsequent IE in high–IE-risk individuals, and a significant association between AP use and reduced IE incidence following these procedures. These data support the American Heart Association, and other, recommendations that those at high IE risk should receive AP before IDP.

Low temperature and temperature decline increase acute aortic dissection risk and burden: A nationwide case crossover analysis at hourly level among 40,270 patients

SummaryBackgroundAcute aortic dissection (AAD) is a life-threatening cardiovascular emergency with high mortality, so identifying modifiable risk factors of AAD is of great public health significance. The associations of non-optimal temperature and temperature variability with AAD onset and the disease burden have not been fully understood.MethodsWe conducted a time-stratified case-crossover study using a nationwide registry dataset from 1,868 hospitals in 313 Chinese cities. Conditional logistic regression and distributed lag models were used to investigate associations of temperature and temperature changes between neighboring days (TCN) with the hourly AAD onset and calculate the attributable fractions. We also evaluated the heterogeneity of the associations.FindingsA total of 40,270 eligible AAD cases were included. The exposure-response curves for temperature and TCN with AAD onset risk were both inverse and approximately linear. The risks were present on the concurrent hour (for temperature) or day (for TCN) and lasted for almost 1 day. The cumulative relative risks of AAD were 1.027 and 1.026 per 1°C lower temperature and temperature decline between neighboring days, respectively. The associations were significant during the non-heating period, but were not present during the heating period in cities with central heating. 23.13% of AAD cases nationwide were attributable to low temperature and 1.58% were attributable to temperature decline from the previous day.InterpretationThis is the largest nationwide study demonstrating robust associations of low temperature and temperature decline with AAD onset. We, for the first time, calculated the corresponding disease burden and further showed that central heating may be a modifier for temperature-related AAD risk and burden.FundingThis work was supported by the National Natural Science Foundation of China (92043301 and 92143301), Shanghai International Science and Technology Partnership Project (No. 21230780200), the Medical Research Council-UK (MR/R013349/1), and the Natural Environment Research Council UK (NE/R009384/1).

Prenatal acute thermophysiological stress and spontaneous preterm birth in Western Australia, 2000-2015: A space-time-stratified case-crossover analysis.

Epidemiologic evidence on acute heat and cold stress and preterm birth (PTB) is inconsistent and based on ambient temperature rather than a thermophysiological index. The aim of this study was to use a spatiotemporal thermophysiological index (Universal Thermal Climate Index, UTCI) to investigate prenatal acute heat and cold stress exposures and spontaneous PTB. We conducted a space-time-stratified case-crossover analysis of 15,576 singleton live births with spontaneous PTB between January 1, 2000 and December 31, 2015 in Western Australia. The association between UTCI and spontaneous PTB was examined with distributed lag nonlinear models and conditional quasi-Poisson regression. Relative to the median UTCI, there was negligible evidence for associations at the lower range of exposures (1st to 25th percentiles). We found positive associations in the 95th and 99th percentiles, which increased with increasing days of heat stress in the first week of delivery. The relative risk (RR) and 95% confidence interval (CI) for the immediate (delivery day) and cumulative short-term (up to six preceding days) exposures to heat stress (99th percentile, 31.2°C) relative to no thermal stress (median UTCI, 13.8°C) were 1.01 (95% CI: 1.01, 1.02) and 1.05 (95% CI: 1.04, 1.06), respectively. Elevated effect estimates for heat stress were observed for the transition season, the year 2005-2009, male infants, women who smoked, unmarried, ≤ 19 years old, non-Caucasians, and high socioeconomic status. Effect estimates for cold stress (1st percentile, 0.7°C) were highest in the transition season, during 2005-2009, and for married, non-Caucasian, and high socioeconomic status women. Acute heat stress was associated with an elevated risk of spontaneous PTB with sociodemographic vulnerability. Cold stress was associated with risk in a few vulnerable subgroups. Awareness and mitigation strategies such as hydration, reducing outdoor activities, affordable heating and cooling systems, and climate change governance may be beneficial. Further studies with the UTCI are required.