Time-stratified Case-crossover Analysis Research Articles

Hourly Exposure to Ultrafine Particle Metrics and the Onset of Myocardial Infarction in Augsburg, Germany

OPS 56: Ultrafine particles exposure and health effects, Beatrix Theater, August 27, 2019, 4:30 PM - 5:30 PM Background: Epidemiological evidence on the health effects of ultrafine particles (UFP) remains insufficient to infer a causal relationship, which is largely due to the different size ranges and exposure metrics examined across studies. Moreover, evidence regarding the association between UFP and cardiovascular disease at a sub-daily timescale is lacking. Objective: To investigate the relationship between different particle metrics, including particle number (PNC), length (PLC), and surface area (PSC) concentrations, and myocardial infarction (MI) at an hourly timescale. Methods: We collected hourly air pollution and meteorological data from fixed urban background monitoring sites and hourly nonfatal MI cases from the MONICA/KORA MI registry in Augsburg, Germany during 2005-2015. We conducted a time-stratified case-crossover analysis with conditional logistic regression to estimate the association between hourly particle metrics and MI cases, adjusted for air temperature and relative humidity. We also examined the independent effects of a certain particle metric in two-pollutant models by adjusting for co-pollutants, including particulate matter with an aerodynamic diameter ≤10 µm or 2.5 µm (PM10, PM2.5), nitrogen dioxide, ozone, and black carbon. Results: Overall, a total of 5,898 cases of nonfatal MI cases were recorded. Interquartile range increases in PNC within the size range of 10-100 nm (UFP), PLC, and PSC were associated with an increase of MI six hours later by 3.27% (95% confidence interval [CI]: 0.27%, 6.37%), 5.71% (95% CI: 1.79%, 9.77%), and 5.56% (95% CI: 1.11%, 10.20%), respectively. No association was observed for PNC within the size range of 100-500 nm. The effect estimates for PLC and PSC remained similar after adjustment for PM and gaseous pollutants. The associations were not modified by individual characteristics, co-pollutants, or air temperature. Conclusions: Transient exposure to particle length and surface area concentrations may trigger the onset of myocardial infraction.

Temperature as a risk factor of emergency department visits for acute kidney injury: a case-crossover study in Seoul, South Korea

BackgroundPrevious studies show that escalations in ambient temperature are among the risk factors for acute kidney injury (AKI). However, it has not been adequately studied in our location, Seoul, South Korea. In this study, we aimed to examine the association between ambient temperatures and AKI morbidity using emergency department (ED) visit data.MethodsWe obtained data on ED visits from the National Emergency Medical Center for 21,656 reported cases of AKI from 2010 to 2014. Time-stratified case-crossover design analysis based on conditional logistic regression was used to analyze short-term effects of ambient temperature on AKI after controlling for relevant covariates. The shape of the exposure–response curve, effect modification by individual demographic characteristics, season, and comorbidities, as well as lag effects, were investigated.ResultsThe odds ratio (OR) per 1 °C increase at lag 0 was 1.0087 (95% confidence interval [CI]: 1.0041–1.0134). Risks were higher during the warm season (OR = 1.0149; 95% CI: 1.0065–1.0234) than during the cool season (OR = 1.0059; 95% CI: 1.0003–1.0116) and even higher above 22.3 °C (OR = 1.0235; 95% CI: 1.0230–1.0239).ConclusionsThis study provides evidence that ED visits for AKI were associated with ambient temperature. Early detection and treatment of patients at risk is important in both clinical and economic concerns related to AKI.

Does ambient ozone air pollution trigger suicide attempts? A case cross-over analysis in Taipei

ABSTRACTEpidemiologic studies indicated that exposure to ambient air pollutants was associated with increased mortality rates attributed to suicide. The objective of this study was to investigate the potential relationship between ambient ozone (O3) levels and daily number of hospital admissions for suicide attempts in Taipei for the period 2008–2012 using a time-stratified case-crossover analysis. In the single-pollutant model (without adjustment for other pollutants), the risk of committing a suicide attempt increased by 9% on warm days and 27% on cool days for each interquartile range (IQR) rise in O3 levels, respectively. The concentration of O3 was thus significantly associated with daily number of suicide attempts both on warm and cool days. In the two-pollutant models, O3 levels remained significant after the inclusion of other air pollutants (particulate matter (PM10), PM2.5, sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO)) on cool days. However, on warm days, no significant correlation was found between O3 levels and reported daily number of suicide attempts. The relationship between O3 and suicide attempts appeared to be dependent upon temperature; however, the basis for these observations requires further investigation.

Ozone pollution and asthma emergency department visits in Fresno, CA, USA, during the warm season (June–September) of the years 2005 to 2015: a time-stratified case-crossover analysis

Fresno, located at the central part of the San Joaquin Valley (SJV), CA, USA, is one of the most air-polluted cities in North America. The present time-stratified case-crossover study investigates whether short-term exposure to ozone (O3) is associated with asthma emergency departments (ED) visits during the high O3 warm seasons (June–September) of 2005 to 2015 in Fresno, CA, USA. A total of 4463 ED visits from 2005 to 2015 in Fresno were identified. The potential effect modification by land use (commercial and residential), sex, race (White, Black, and Hispanic), and age (2–5, 6–18, 19–40, 41–64, and > = 65) was investigated. A 5 ppb increase in the concentration of O3 at the lag 0–14 was associated with 33.6% increase in the odds of having an asthma ED visit [OR 1.336 (95% confidence intervals 1.262, 1.414)]. People living in commercial areas (OR 1.470 (95% confidence intervals 1.353, 1.597) at lag 0–14) experienced higher odds of visiting the ED due to asthma when compared to those living in residential areas (OR 1.193 (95% confidence intervals 1.084, 1.313) at lag 0–14). Sex was not a modifier in this study. Blacks and Hispanics showed faster response to O3 exposure. The association between O3 exposure and asthma ED visits was positive among all age groups, but greater among 6 to 18 years. Ozone exposure is associated with asthma ED visits in Fresno during the warm seasons (June–September) of 2005 to 2015.

Temporal variations in the triggering of myocardial infarction by air temperature in Augsburg, Germany, 1987-2014.

The association between air temperature and mortality has been shown to vary over time, but evidence of temporal changes in the risk of myocardial infarction (MI) is lacking. We aimed to estimate the temporal variations in the association between short-term exposures to air temperature and MI in the area of Augsburg, Germany. Over a 28-years period from 1987 to 2014, a total of 27310 cases of MI and coronary deaths were recorded. Daily meteorological parameters were measured in the study area. A time-stratified case-crossover analysis with a distributed lag non-linear model was used to estimate the risk of MI associated with air temperature. Subgroup analyses were performed to identify subpopulations with changing susceptibility to air temperature. Results showed a non-significant decline in cold-related MI risks. Heat-related MI relative risk significantly increased from 0.93 [95% confidence interval (CI): 0.78-1.12] in 1987-2000 to 1.14 (95% CI: 1.00-1.29) in 2001-14. The same trend was also observed for recurrent and non-ST-segment elevation MI events. This increasing population susceptibility to heat was more evident in patients with diabetes mellitus and hyperlipidaemia. Future studies using multicentre MI registries at different climatic, demographic, and socioeconomic settings are warranted to confirm our findings. We found evidence of rising population susceptibility to heat-related MI risk from 1987 to 2014, suggesting that exposure to heat should be considered as an environmental trigger of MI, especially under a warming climate.

Relationship between ozone air pollution and daily suicide mortality: a time-stratified case-crossover study in Taipei

ABSTRACTSeveral studies suggested short-term exposure to air pollution might be associated with suicide mortality, although results have been inconsistent and vary depending upon the type of air contaminants. While seasonal variation associated with suicide was reported to occur and that in the spring and early summer there are peaks in ozone (O3) distribution, the relationship between these two parameters is not known. The aim of this study was to examine the potential association between O3 levels and daily mortality rate related to suicide in Taipei for the period 2004–2008 using a time-stratified case-crossover analysis. In our single pollutant model without adjustment for other pollutants, the risk of suicide increased by 11% on warm days and 15% on cool days for each interquartile range (IQR) rise in O3 concentration, respectively. The relationship was positive but did not reach significance. In our two-pollutant models, O3 remained non-significant on warm days after inclusion of one of any other ambient air contaminants into the model. However, on cool days, a significant association was found between O3 levels and enhanced risk of mortality due to suicide after nitrogen dioxide (NO2) or carbon monoxide (CO) were included. The overall positive but not significant findings of elevated risk of mortality frequently attributed to suicide on days with higher O3 levels suggest that outdoor exposures to this gaseous contaminant may contribute to increases in daily mortality rate related to suicide.

Spatial variation in lag structure in the short-term effects of air pollution on mortality in seven major South Korean cities, 2006–2013

Lag is one of the major uncertainties in the heterogeneity of short-term effects of particulate matter with aerodynamic diameter <10 μm (PM10) on mortality. This study aimed to explore spatial variations in extended lag effects of PM10 on all-cause mortality, cardiovascular mortality and respiratory mortality in seven major South Korean cities over a period spanning 2006–2013. We did time-series analysis using generalized linear models and adjusted for temporal trend, day of the week, holiday, influenza epidemic, and weather. Single lag models and distributed lag models were extensively compared, specifically in terms of lag interval, and adjustment for temporal trend. We also conducted a time-stratified case-crossover analysis. Multivariate meta-regressions with city characteristic variables were conducted in order to assess spatial variation in the lag structure. When considering up to previous 45 days of exposure, we found longer lag associations between PM10 and mortality, particularly in all-cause mortality and respiratory mortality. SO2, the ratio of SO2 to PM10 and gross regional domestic product were all found to positively contribute towards the associations between PM10 and all-cause mortality and cardiovascular mortality. Ulsan (Korea's largest industrial city) was found to have the strongest cumulative percentage increases in all-cause mortality and cardiovascular mortality per 10 μg/m3 increase of PM10: 4.9% (95% CI: 2.5, 7.3) and 4.3% (95% CI: −0.9, 9.7) respectively. Busan (Korea's largest seaport city) was found to have the highest cumulative percentage increase in respiratory mortality with an 8.2% increase (95% CI: 2.8, 13.8). In summary, the short-term effects of PM10 on mortality may persist over a period of not just few weeks but longer than a month, and may differ according to regional economy. This study provides public health implication that, in order to minimize the health effects of PM, air quality interventions should focus on not only particulate pollution but also gaseous pollution, such as SO2.

Short-term air pollution exposure and emergency department visits for amyotrophic lateral sclerosis: A time-stratified case-crossover analysis

BackgroundAmyotrophic lateral sclerosis (ALS) is a progressive and devastating neurodegenerative disease, eventually leading to respiratory failure. Although the only currently available therapeutic interventions merely slow the disease progression, few studies have examined risk factors associated with ALS exacerbation and progression. ObjectiveTo investigate the association between exposure to short-term air pollution and acute exacerbation of ALS requiring emergency department (ED) visit. MethodsWe identified from the national emergency database of Korea 617 patients who visited EDs in Seoul with ALS as a primary cause during the period 2008–2014. We estimated short-term exposure to particles <2.5 μm (PM2.5), particles <10 μm (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO). We conducted a conditional logistic regression with a time-stratified case-crossover design to examine the association between ED visits for ALS and short-term exposure to interquartile range (IQR) increase and upper quartile levels of air pollutants on the day of the ED visit, compared to the control days matched to day of the week, month, and year. ResultsThe risk of ED visits for ALS was significantly associated with an IQR increase of PM2.5 [Odds ratio (OR) = 1.21; 95% confidence interval (CI): 1.08, 1.35], PM10 [OR = 1.13; 95% CI: 1.02, 1.25], SO2 [OR = 1.19; 95% CI: 1.01, 1.41], and CO [OR = 1.19; 95% CI: 1.03, 1.36]. Exposure to the highest quartiles of PM2.5 and PM10 showed higher associations with ED visits for ALS [OR = 1.40; 95% CI: 1.06, 1.85 and OR = 1.33; 95% CI: 1.00, 1.77]. DiscussionWe provide new evidence that exposure to short-term air pollution may increase the risk of acute exacerbation of ALS. Further studies are warranted to understand the underlying mechanisms.

Ambient air pollution and the hospital outpatient visits for eczema and dermatitis in Beijing: a time-stratified case-crossover analysis.

Eczema and dermatitis are a group of common skin conditions with multiple risk factors. Evidence of the effects of air pollutants on eczema and dermatitis remains limited. This study aimed to investigate the effects of short-term exposure to air pollution on eczema and dermatitis in Beijing. A time-stratified case-crossover design was used to assess the associations between short-term changes in air pollution and the hospital outpatient visits for eczema and dermatitis in Beijing. A total of 157 595 outpatient visits for eczema and dermatitis were recorded from April 1, 2012 to April 30, 2014. All pollutants showed significant positive associations with the number of outpatient visits for eczema and dermatitis on lag 0 (the current day). Per IQR increase in PM2.5, PM10, NO2 and SO2 was associated with 3.81% (95% CI: 2.92-4.7%), 3.18% (95% CI: 2.39-3.97%), 5.43% (95% CI: 4.43-6.43%) and 5.57% (95% CI: 4.55-6.58%) increases in outpatient visits for eczema and dermatitis on lag 0. Associations of air pollutants with eczema and dermatitis outpatient visits varied with the seasons and were stronger among older people and females. Also, an association of consecutive days' high concentration pollution with increased outpatient visits was observed. Exposure to air pollution increases the exacerbation of eczema and dermatitis and stronger positive associations between air pollutants and outpatient visits for eczema and dermatitis were found among the aged, females and when high concentration air pollution occurs continuously.

Impact of Maximum Air Temperature on Ambulance Transports Owing to Heat Stroke During Spring and Summer in Tottori Prefecture, Japan: A Time-stratified Case-crossover Analysis

The frequency and intensity of hot weather have increased. In Japan, there have been many studies of the relationship between ambulance transports owing to heat stroke (ATHS) and high air temperature in the summer season. However, there have been very few reports focusing on ATHS in spring. Therefore, we investigated the effect of the maximum air temperature on ATHS not only in summer but also in spring, to help with development of effective measures to prevent heat stroke. We obtained daily ATHS and meteorological data from April to September in 2017 in Tottori Prefecture. We used a time-stratified case-crossover method for data analysis. A total 382 cases of ATHS were identified from April to September in 2017 in Tottori. The number of cases was highest in July, followed by August and May. Maximum air temperature was significantly linked to ATHS. The risk of ATHS was increased 1.13 times when maximum air temperature rose by 1°C. In summer, the risk on extremely hot days (maximum air temperature ≥ 35°C) increased by 5.55 times or more compared with that on days below 30 °C (< 30°C). The risk was approximately four times greater on hot days (≥ 30°C and < 35°C) than that on relatively cooler days (< 30°C) during the spring months of April through May. Maximum air temperature was significantly linked to ATHS. It is necessary to pay particular attention to heat stroke prevention not only on extremely hot days in summer but also on hot days in the spring.

Ozone and cardiac arrest: The role of previous hospitalizations

BackgroundSeveral studies have reported associations between exposure to particulate matter and incidence of out-of-hospital cardiac arrest (OHCA) and some have observed associations with ozone (O3). There are no studies investigating susceptibility based on previous disease history to short-term O3 exposure and the risk of OHCA. AimTo investigate the role of previous cardiovascular-related hospitalizations in modifying the associations between the risk of OHCA and short-term increase in O3 concentrations. MethodsA time-stratified case-crossover analysis of 11,923 OHCA registered in the Swedish Register for Cardiopulmonary Resuscitation from 2006 to 2014 was performed. Using personal identification numbers, OHCA were linked to all previous hospitalizations in Sweden since 1987 to create susceptible groups based on the principal diagnosis code at discharge. Susceptibility was based on hospitalization for i) acute myocardial infarction; ii) heart failure; iii) arrhythmias; iv) diabetes; v) hypertension; and vi) stroke. Moving 2 and 24-h averages for O3, PM2.5, PM10, and NO2 were constructed from hourly averages. ResultsA 10 μg/m3 higher 2-h average O3 concentration was associated with a 2% higher risk of OHCA (95% CI, 0% 3%). Associations were similar for 24-h average O3 and in individuals with or without hospitalizations for AMI, heart failure, diabetes, hypertension or stroke. Individuals with previous hospitalizations for arrhythmias had a lower risk of OHCA with higher O3. No associations were observed for other pollutants. ConclusionsShort-term exposure to O3 was associated with an elevated risk of OHCA, however, previous hospitalizations for cardiovascular diseases were not associated with additionally augmented risks.

Ozone pollution and asthma emergency department visits in the Central Valley, California, USA, during June to September of 2015: a time-stratified case-crossover analysis

Objective: The San Joaquin Valley (SJV) exceeds the state and national standards for ozone (O3). This study investigates whether short-term exposure to O3 is associated with asthma emergency department (ED) visits. Methods: We identified 1,101 ED visits in June–September of 2015 in SJV, California, who lived within 15 km of active air monitors. Conditional logistic regression models were used to obtain the odds ratio (OR) and 95% confidence interval (CI) associated with an interquartile (IQR) increase in ozone. We explored the potential effect modification by sex (female and male), race (White, Black and Hispanic), age (2–5, 6–18, 19–40, 41–64 and > = 65) and county (Merced, Madera, Kings, Fresno and Kern). Results: An IQR range (18.1 ppb) increase in O3 exposure three days before an asthma attack (lag 3) was associated with a 6.6% [OR: 1.066 (95% CI: 1.032, 1.082)] increase in the odds of having an asthma ED visit. The overall ORs differed across age groups and races/ethnicities, with strongest for children aged 6–18 years [OR: 1.219 (95% CI: 1.159, 1.280)], adults 19–40 years [OR: 1.102 (95% CI: 1.053, 1.154)] and Blacks [OR: 1.159 (95% CI: 1.088, 1.236)], respectively. O3 exposure was not positively associated with asthma ED visits for Whites, while it was for other underrepresented groups. Fresno had the highest number of asthma ED visits and positive association among all five counties. Conclusion: We found that O3 exposure is associated with asthma ED visits in the SJV.

Associations of Source-apportioned Fine Particles with Cause-specific Mortality in California.

Exposure to ambient fine particulate matter (PM2.5) has been linked with premature mortality, but sources of PM2.5 have been less studied. We evaluated associations between source-specific PM2.5 exposures and cause-specific short-term mortality in eight California locations from 2002 to 2011. Speciated PM2.5 measurements were source-apportioned using Positive Matrix Factorization into eight sources and combined with death certificate data. We used time-stratified case-crossover analysis with conditional logistic regression by location and meta-analysis to calculate pooled estimates. Biomass burning was associated with all-cause mortality lagged 2 days after exposure (lag2) (% changelag2 in odds per interquartile range width increase in biomass burning PM2.5 = 0.8, 95% confidence interval [CI] = 0.2, 1.4), cardiovascular (% changelag2 = 1.3, 95% CI = 0.3, 2.4), and ischemic heart disease (% changelag2 = 2.0, 95% CI = 0.6, 3.5). Vehicular emissions were associated with increases in cardiovascular mortality (% changelag0 = 1.4, 95% CI = 0.0, 2.9). Several other sources exhibited positive associations as well. Many findings persisted during the cool season. Warm season biomass burning was associated with respiratory/thoracic cancer mortality (% changelag1 = 5.9, 95% CI = 0.7, 11.3), and warm season traffic was associated with all-cause (% changelag0 = 1.9, 95% CI = 0.1, 3.6) and cardiovascular (% changelag0 = 2.9, 95% CI = 0.1, 5.7) mortality. Our results suggest that acute exposures to biomass burning and vehicular emissions are linked with cardiovascular mortality, with additional sources (i.e., soil, secondary nitrate, secondary sulfate, aged sea salt, and chlorine sources) showing associations with other specific mortality types.

The Relationship Between Ambient Air Pollution and Acute Ischemic Stroke: A Time-Stratified Case-Crossover Study in a City-State With Seasonal Exposure to the Southeast Asian Haze Problem

Studies are divided on the short-term association of air pollution with stroke. Singapore is exposed to seasonal transboundary haze. We aim to investigate the association between air pollution and stroke incidence in Singapore. We performed a time-stratified case-crossover analysis on all ischemic stroke cases reported to the Singapore Stroke Registry from 2010 to 2015. Exposure on days was compared with control days on which exposure did not occur. Control days were chosen on thesame day of the week earlier and later in the same month in the same year. We fitted a conditional Poisson regression model to daily stroke incidence that included Pollutant Standards Index and environmental confounders. The index was categorized according to established classification (0 to 50=good, 51 to 100=moderate, and ≥101=unhealthy). We assessed the relationship between stroke incidence and Pollutant Standards Index in the entire cohort and in predetermined subgroups of individual-level characteristics. There were 29,384 ischemic stroke cases. Moderate and unhealthy Pollutant Standards Index levels showed association with stroke occurrence, with incidence risk ratio 1.10 (95% confidence interval 1.06 to 1.13) and 1.14 (95% confidence interval 1.03 to 1.25), respectively. Subgroup analyses showed generally significant association, except in Indians and nonhypertensive patients. The association was significant in subgroups aged 65 years or older, women, Chinese, nonsmokers and those with history of diabetes, hypertension, and hyperlipidemia. Stratified by age and smoking, the risk diminished in smokers of all ages. Risk remained elevated for 5 days after exposure. We found a short-term elevated risk of ischemic stroke after exposure to air pollution. These findings have public health implications for stroke prevention and emergency health services delivery.

The effect of ambient particle matters on hospital admissions for cardiac arrhythmia: a multi-city case-crossover study in China

BackgroundThe relationship between particle matters (PMs) and cardiac arrhythmia has been investigated in numerous studies. However, evidence from developing countries is limited. The aim of this study was to evaluate the association between ambient PMs and hospital admissions for cardiac arrhythmia in China and to examine the potential effect modifiers.MethodsA time-stratified case-crossover analysis was conducted in 26 large Chinese cities. In total, we identified 175,265 hospital admissions for cardiac arrhythmia between January 2014 and December 2015 from electronic hospitalization summary reports. Conditional logistic regression was performed to estimate the percentage changes in cardiac arrhythmia admissions in relation to interquartile range increases in air pollutants. Age, gender and prespecified comorbid health conditions including hypertension, diabetes, congestive heart failure and hyperlipidemia were stratified to evaluate susceptibility factors.ResultsPMs levels were positively associated with the number of hospital admissions for cardiac arrhythmia. Both PM2.5 and PM10 had the strongest impact on lag 2 days. An interquartile range increase in PM2.5 (47.5 μg/m3) and PM10 (76.9 μg/m3) concentrations on lag 2 days was associated with increments of 2.09% (95%CI, 1.58–2.60%) and 2.33% (95%CI, 1.68–2.97%) in hospital admission for cardiac arrhythmia, respectively. Evidence of effect modification by age and comorbid diabetes was observed. The elderly (> 65 years) and patients with comorbid diabetes were more likely to be hospitalized for cardiac arrhythmia following exposure to high levels of PMs.ConclusionsThis study found an increased risk of arrhythmia admissions associated with PM2.5 and PM10 levels among 26 Chinese cities. The associations of PMs with arrhythmia admissions were stronger in aged population and people with diabetes.

Air Pollution and Suicide in 10 Cities in Northeast Asia: A Time-Stratified Case-Crossover Analysis.

Background:There is growing evidence suggesting an association between air pollution and suicide. However, previous findings varied depending on the type of air pollutant and study location.Objectives:We examined the association between air pollutants and suicide in 10 large cities in South Korea, Japan, and Taiwan.Methods:We used a two-stage meta-analysis. First, we conducted a time-stratified case-crossover analysis to estimate the short-term association between nitrogen dioxide (), sulfur dioxide (), and particulate matter [aerodynamic diameter (), aerodynamic diameter (), and ] and suicide, adjusted for weather factors, day-of-week, long-term time trends, and season. Then, we conducted a meta-analysis to combine the city-specific effect estimates for , , and across 10 cities and for and across 3 cities. We first fitted single-pollutant models, followed by two-pollutant models to examine the robustness of the associations.Results:Higher risk of suicide was associated with higher levels of , , , and over multiple days. The combined relative risks (RRs) were 1.019 for (95% confidence interval [CI]: 0.999, 1.039), 1.020 for (95% CI: 1.005, 1.036), 1.016 for (95% CI: 1.004, 1.029), and 1.019 for (95% CI: 1.005, 1.033) per interquartile range (IQR) increase in the 0–1 d average level of each pollutant. We found no evidence of an association for . Some of the associations, particularly for and , were attenuated after adjusting for a second pollutant.Conclusions:Our findings suggest that higher levels of air pollution may be associated with suicide, and further research is merited to understand the underlying mechanisms. https://doi.org/10.1289/EHP2223

Temperature Variability may Trigger Spontaneous Early Delivery in Shenzhen, China: A Case-Crossover Study

Background/Aim: Early delivery (&lt;39 gestational weeks), including early-term and preterm birth, is related to higher infant mortality and neonatal morbidity. Previous studies have shown that extreme temperatures increase the risk of early delivery, however the effect of unstable weather conditions remains unclear. This study aimed to investigate the association between temperature variability (TV) and early delivery in Shenzhen, China. Methods: We obtained records of 293,463 spontaneous early deliveries from Shenzhen Obstetric Data Reporting System during 2003-2012. Meteorological and air quality data were collected from meteorological bureau. TV during 6 exposure windows (preceding 2 days, 3 days, up to 7 days) , was separately calculated from the standard deviation of minimum and maximum temperatures (Yuming Guo, 2016). A time-stratified case-crossover analysis with conditional Poisson regression models was used to assess the relationship between TVs and early delivery, adjusting for mean temperature, humidity and air quality index. Results: TV ranged from 0 to 6 °C. The elevated TV0-1, TV0-2 and TV0-3 significantly increased the risk of overall early delivery, especially for preterm birth, and the effect of TV0-1 was the most obvious. Compared with the median of TV0-1 (0.5 °C), the relative risks for early delivery and preterm birth were 1.005 (95%CI: 1.000-1.011) and 1.019 (95%CI: 1.006-1.032) at 99th percentile of TV0-1 (2.74°C), respectively. TV0-1 effect was modified by delivery season, maternal education and parity. Low educated mothers, multiparae or those deliveried in spring and winter were more likely to delivery early due to TV. By stratified analyses, the TV0-1 increased the early delivery risk due to preterm labor, while the risk of early delivery following premature rupture of membrane declined. Conclusions: Temperature variability may trigger spontaneous early delivery due to preterm labor, especially during spring and winter. Pregnant women with lower education and multi-parity should pay more attention to unstable weather.

Ambient Temperature and Sudden Infant Death Syndrome in the United States.

Sudden infant death syndrome (SIDS) is a leading cause of infant mortality in the United States. While thermal stress is implicated in many risk factors for SIDS, the association between ambient temperature and SIDS remains unclear. We obtained daily individual-level infant mortality data and outdoor temperature data from 1972 to 2006 for 210 US cities. We applied a time-stratified case-crossover analysis to determine the effect of ambient temperature on the risk of SIDS by season. We stratified the analysis by race, infant age, and climate. There were a total of 60,364 SIDS cases during our study period. A 5.6°C (10°F) higher daily temperature on the same day was associated with an increased SIDS risk of 8.6% (95% confidence interval [CI] = 3.6%, 13.8%) in the summer, compared with a 3.1% decrease (95% CI = -5.0%, -1.3%) in the winter. Summer risks were greater among black infants (18.5%; 95% CI = 9.3%, 28.5%) than white infants (3.6%; 95% CI = -2.3%, 9.9%), and among infants 3-11 months old (16.9%; 95% CI = 8.9%, 25.5%) than infants 0-2 months old (2.7%; 95% CI = -3.5%, 9.2%). The temperature-SIDS association was stronger in climate clusters in the Midwest and surrounding northern regions. Temperature increases were associated with an elevated risk of SIDS in the summer, particularly among infants who were black, 3 months old and older, and living in the Midwest and surrounding northern regions.

Particulate Matter and Risk of Hospital Admission in the Kathmandu Valley, Nepal: A Case-Crossover Study.

Air pollution is known to lead to a substantial health burden, but the majority of evidence is based on data from North America and Europe. Despite rising pollution levels, very limited information is available for South Asia. We investigated the impact of particulate matter with an aerodynamic diameter less than or equal to 10 μm (PM10) on hospitalization, by cause and subpopulation, in the Kathmandu Valley, an understudied and rapidly urbanizing region in Nepal. Individual-level daily inpatient hospitalization data (2004-2007) were collected from each of 6 major hospitals, as Nepal has no central data collection system. Time-stratified case-crossover analysis was used with interaction terms for potential effect modifiers (e.g., age, sex, and socioeconomic status), with adjustment for day of the week and weather. Daily PM10 concentrations averaged 120 μg/m3, with the daily maximum reaching 403 μg/m3. A 10-μg/m3 increase in PM10 level was associated with increased risks of hospitalization of 1.00% (95% confidence interval (CI): 0.62, 1.38), 1.70% (95% CI: 0.18, 3.25), and 2.29% (95% CI: 0.18, 4.43) for total, respiratory, and cardiovascular admissions, respectively. We did not find strong evidence of effect modification by age, sex, or socioeconomic status. These results, in combination with the high levels of exposure, indicate a potentially serious human health burden from air pollution in the Kathmandu Valley.

Associations of PM2.5 and Black Carbon with Hospital Emergency Room Visits during Heavy Haze Events: A Case Study in Beijing, China.

In January 2013, severe haze events over northeastern China sparked substantial health concerns. This study explores the associations of fine particulate matter less than 2.5 μm (PM2.5) and black carbon (BC) with hospital emergency room visits (ERVs) during a haze season in Beijing. During that period, daily counts of ERVs for respiratory, cardiovascular and ocular diseases were obtained from a Level-3A hospital in Beijing from 1 December 2012 to 28 February 2013, and associations of which with PM2.5 and BC were estimated by time-stratified case-crossover analysis in single- and two-pollutant models. We found a 27.5% (95% confidence interval (CI): 13.0, 43.9%) increase in respiratory ERV (lag02), a 19.4% (95% CI: 2.5, 39.0%) increase in cardiovascular ERV (lag0), and a 12.6% (95% CI: 0.0, 26.7%) increase in ocular ERV (lag0) along with an interquartile range (IQR) increase in the PM2.5. An IQR increase of BC was associated with 27.6% (95% CI: 9.6, 48.6%) (lag02), 18.8% (95% CI: 1.4, 39.2%) (lag0) and 11.8% (95% CI: −1.4, 26.8%) (lag0) increases for changes in these same health outcomes respectively. Estimated associations were consistent after adjusting SO2 or NO2 in two-pollutant models. This study provides evidence that improving air quality and reducing haze days would greatly benefit the population health.