Relative Risk Of Hospital Admission Research Articles

Short term exposure to low level ambient fine particulate matter and natural cause, cardiovascular, and respiratory morbidity among US adults with health insurance: case time series study

ObjectiveTo estimate the excess relative and absolute risks of hospital admissions and emergency department visits for natural causes, cardiovascular disease, and respiratory disease associated with daily exposure to fine particulate...

A retrospective registry analysis of the transport‐related health burden of wheeled recreational devices in Queensland, Australia

ObjectiveEvaluate injury patterns from wheeled recreational devices (WRD) in the public space and explore risk factors for hospital admission. MethodA cross‐sectional analysis of WRD injury prevalence and risk factors for hospital admissions was conducted using data from the Queensland Injury Surveillance Unit (QISU) database for 2007 to 2017. Descriptive statistics and a log‐binomial regression model were used to calculate adjusted relative risk for hospital admission. ResultsMost WRD injury in the public space was related to stand‐alone WRD injury events such as falls, with few reported WRD users being hit by vehicles from 2007 to 2017. Stand‐alone WRD injury events had a higher independent risk of hospital admissions when injured in the head/neck/face (RR 2.08, 95%CI 1.6 to 2.8, p<0.001), and when the injury was a fracture (RR 2.57, 95%CI 2.1 to 3.3, p<0.001) or a brain injury (RR 3.19, 95%CI 2.5 to 4.1, p<0.001). ConclusionHead, brain and facial injuries and fractures are leading preventable factors for hospital admissions due to WRD injury. These types of injuries generate a preventable burden to the health system. Implications for public healthThe results support the need to consider legislation regarding mandatory helmet use for non‐motorised WRD when used on public roads and footpaths, while further research is conducted. This strategy could reduce the long‐term health outcomes associated with head, face and brain injury in young commuters.

Does climate change affect the chronobiological trends in occurrence of acute coronary syndromes?

Abstract Funding Acknowledgements Type of funding sources: None. Background Acute coronary syndromes (ACS) are the leading cause of death all over the world, in the last years chronobiology of their occurrence has been changing. Purpose The aim of this study was to assess the influence of climate change on hospital admissions due to ACS. Methods Medical records of 10,529 patients hospitalized for ACS in 2008–2017 were examined. Weather conditions data were obtained from the Institute of Meteorology. Results Among the patients, 3537 (33.6%) were hospitalized for STEMI, 3947 (37.5%) for NSTEMI, and 3045 (28.9%) for UA. The highest seasonal mean for ACS was recorded in spring (N = 2782, mean = 2.52, SD = 1.7; OR 1.07; 95% CI 1.0-1.2; P = 0.049) and it was a season with the highest temperature changes day to day (Δ temp.=11.7). On the other hand, every 10ºC change in temperature was associated with an increased admission due to ACS by 13% (RR 1.13; 95% CI 1.04-1.3; P = 0.008). Analysis of weekly changes showed that the highest frequency of ACS occurred on Thursday (N = 1703, mean = 2.7, SD = 1.9; OR 1.16; 95% CI 1.0-1.23; P = 0.004), in STEMI subgroup it was Monday (N = 592, mean = 0.9, SD = 1.6, OR 1.2; 95% CI 1.1-1.4; P = 0.002). Sunday was associated with decreased admissions due to all types of ACS (N = 1098, mean = 1.7, SD = 1.4; OR 0.69; 95% CI 0.6-0.8, P &amp;lt; 0.001). In the second half of the study period (2013-2018) the relative risks of hospital admissions due to ACS were 1.043 (95%CI: 1.009-1.079, P = 0.014, lag 0) and 0.957 (95%CI: 0.925-0.990, P = 0.010, lag 1) for each 10ºC decrease in temperature; 1.049 (95% CI: 1.015-1.084, P = 0.004, lag 0) and 1.045 (95%CI: 1.011-1.080, P = 0.008, lag 1) for each 10 hPa decrease in atmospheric pressure and 1.180 (95% CI: 1.078-1.324, P = 0.007, lag 0) for every 10ºC change in temperature. For the first half of the study the risk was significantly lower. Conclusion We observed a shift in the seasonal peak of ACS occurrence from winter to spring which may be related to temperature fluctuation associated with climate change in this season. The lowest frequency of ACS took place on weekends. Atmospheric changes had a much more pronounced effect on admissions due to ACS in the second half of the analyzed period, which is in line with the dynamics of global climate change.

National Trends in Emergency Room Visits of Dialysis Patients for Adverse Drug Reactions

Background: Various medications are cleared by the kidneys, therefore patients with impaired renal function, especially dialysis patients are at risk for adverse drug events (ADEs). There are limited studies on ADEs in maintenance dialysis patients. Methods: We utilized a nationally representative database, the Nationwide Emergency Department Sample, from 2008 to 2013, to compare emergency department (ED) visits for dialysis and propensity matched non-dialysis patients. Log binomial regression was used to calculate relative risk of hospital admission and logistic regression to calculate ORs for in-hospital mortality while adjusting for patient and hospital characteristics. Results: While ED visits for ADEs decreased in both groups, they were over 10-fold higher in dialysis patients than non-dialysis patients (65.8–88.5 per 1,000 patients vs. 4.6–5.4 per 1,000 patients respectively, p < 0.001). The top medication category associated with ED visits for ADEs in dialysis patients is agents primarily affecting blood constituents, which has increased. After propensity matching, patient admission was higher in dialysis patients than non-dialysis patients, (88 vs. 76%, p < 0.001). Dialysis was associated with a 3% increase in risk of admission and 3 times the odds of in-hospital mortality (adjusted OR 3, 95% CI 2.7–2.3.3). Conclusions: ED visits for ADEs are substantially higher in dialysis patients than non-dialysis patients. In dialysis patients, ADEs associated with agents primarily affecting blood constituents are on the rise. ED visits for ADEs in dialysis patients have higher inpatient admissions and in-hospital mortality. Further studies are needed to identify and implement measures aimed at reducing ADEs in dialysis patients.

Association between fine particulate air pollution and hospital admissions for chest pain in a subtropical city: Taipei, Taiwan

ABSTRACT This study determined the association between fine particles (PM2.5) levels and hospital admissions for chest pain (CP) in Taipei, Taiwan. Hospital admissions for CP and ambient air pollution data for Taipei were obtained for the period 2009–2013. The relative risk of hospital admissions was estimated using a case-crossover approach, after controlling for weather variables, day of the week, seasonality, and long-term time trends. For single-pollutant models (without adjustment for other pollutants), increased frequency of CP admissions was significantly associated with PM2.5 levels on warm days (>23°C), with an interquartile range rise correlated with a 15% (95% confidence interval = 11–31%) elevation in number of CP admissions. In two-pollutant models, PM2.5 remained significant after inclusion of each of the other four pollutants: sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) on warm days. Generally, no marked associations were observed between PM2.5 levels and risk of CP admissions on cool days in both single- and two-pollutant models. This study provides evidence that higher PM2.5 concentrations enhance the risk of hospital admissions for CP on warm days.

Short-term effects of fine particulate air pollution on hospital admissions for hypertension: A time-stratified case-crossover study in Taipei

ABSTRACTThis study was undertaken to determine whether there was a correlation between fine particle (PM2.5) levels and hospital admissions for hypertension in Taipei, Taiwan. Hospital admissions for hypertension and ambient air pollution data for Taipei were obtained for the period from 2009 to 2013. The relative risk of hospital admissions was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single pollutant model (without adjustment for other pollutants), the risk of hospital admissions for hypertension was estimated to increase by 12% on warm days (>23°C) and 2% on cool days (<23°C), respectively. There was no indication of an association between levels of PM2.5 and risk of hospital admissions for hypertension. In two-pollutant model, PM2.5 remained nonsignificant after inclusion of any of the other air pollutants (SO2, NO2, CO, or O3) both on warm and cool days, but a numerically greater response was seen on warm days. Data thus indicate that in Taipei, hospital admissions for hypertension occur as a consequence of factors not related to ambient air exposure.

Wildfire-specific Fine Particulate Matter and Risk of Hospital Admissions in Urban and Rural Counties.

The health impacts of wildfire smoke, including fine particles (PM2.5), are not well understood and may differ from those of PM2.5 from other sources due to differences in concentrations and chemical composition. First, for the entire Western United States (561 counties) for 2004-2009, we estimated daily PM2.5 concentrations directly attributable to wildfires (wildfires-specific PM2.5), using a global chemical transport model. Second, we defined smoke wave as ≥2 consecutive days with daily wildfire-specific PM2.5 > 20 μg/m, with sensitivity analysis considering 23, 28, and 37 μg/m. Third, we estimated the risk of cardiovascular and respiratory hospital admissions associated with smoke waves for Medicare enrollees. We used a generalized linear mixed model to estimate the relative risk of hospital admissions on smoke wave days compared with matched comparison days without wildfire smoke. We estimated that about 46 million people of all ages were exposed to at least one smoke wave during 2004 to 2009 in the Western United States. Of these, 5 million are Medicare enrollees (≥65 years). We found a 7.2% (95% confidence interval: 0.25%, 15%) increase in risk of respiratory admissions during smoke wave days with high wildfire-specific PM2.5 (>37 μg/m) compared with matched non smoke wave days. We did not observe an association between smoke wave days with wildfire-specific PM2.5 ≤ 37 μg/mand respiratory or cardiovascular admissions. Respiratory effects of wildfire-specific PM2.5 may be stronger than that of PM2.5 from other sources. Short-term exposure to wildfire-specific PM2.5was associated with risk of respiratory diseases in the elderly population in the Western United States during severe smoke days. See video abstract at, http://links.lww.com/EDE/B137.

Coarse Particulate Air Pollution Associated with Increased Risk of Hospital Admissions for Respiratory Diseases in a Tropical City, Kaohsiung, Taiwan.

This study was undertaken to determine whether there was an association between coarse particles (PM₂.₅-₁₀) levels and frequency of hospital admissions for respiratory diseases (RD) in Kaohsiung, Taiwan. Hospital admissions for RD including chronic obstructive pulmonary disease (COPD), asthma, and pneumonia, and ambient air pollution data levels for Kaohsiung were obtained for the period from 2006 to 2010. The relative risk of hospital admissions for RD was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single pollutant model (without adjustment for other pollutants), increased rate of admissions for RD were significantly associated with higher coarse PM levels only on cool days (&lt;25 °C), with a 10 µg/m³ elevation in PM₂.₅-₁₀ concentrations associated with a 3% (95% CI = 1%-5%) rise in COPD admissions, 4% (95% CI = 1%-7%) increase in asthma admissions, and 3% (95% CI = 2%-4%) rise in pneumonia admissions. No significant associations were found between coarse particle levels and the number of hospital admissions for RD on warm days. In the two-pollutant models, PM₂.₅-₁₀ levels remained significantly correlated with higher rate of RD admissions even controlling for sulfur dioxide, nitrogen dioxide, carbon monoxide, or ozone on cool days. This study provides evidence that higher levels of PM₂.₅-₁₀ enhance the risk of hospital admissions for RD on cool days.

Effects of Air Pollutant Exposure on Acute Myocardial Infarction, According to Gender.

Background:There is evidence of the effects of air pollution on hospital admissions due to cardiovascular diseases, including myocardial infarction.Objective:To estimate the association between exposure to air pollutants and hospital admissions due to myocardial infarction according to gender, between January 1st 2012 and December 31st 2013, in São Jose dos Campos-SP.Methods:An ecological time series study was carried out with daily data of admissions due to AMI, pollutants CO, O3, PM10, SO2, and NO2, according to gender. We used the Poisson regression generalized linear model to estimate the relative risks of hospital admissions with lags of 0-5 days, adjusted for temperature, humidity, seasonality and days of the week.Results:There were 1837 admissions for ischemic heart diseases, with 636 women and 1201 men. For females, the risks were significant for CO in lag 0 (RR = 1,09), lag1 (RR = 1,08) and lag 5 (RR = 1,10) and SO2 in lag 0 (RR = 1,10) and 3 (RR = 1,09). For men there was significance of the CO in, lag 3 and lag 5 (RR = 1,05). There was significance, regardless of gender, for CO at lag 1 (RR = 1,05) and lag 5 (RR = 1,07) and lag 0 for SO2 (RR = 1,06).Conclusion:The data presented show the important role of CO and SO2 in the genesis of myocardial infarction admissions, and responses to pollutant exposure are different if analyzed by gender and together - hence the importance of a stratified analyses.

Seasonal Changes in Hospital Admissions for Pulmonary Embolism in Metropolitan Areas of Tokyo (from the Tokyo Cardiovascular Care Unit Network)

Although several studies have shown the relation between temperature/atmospheric pressure and pulmonary embolism (PE), their results are inconsistent. Furthermore, diurnal temperature range (DTR) and diurnal pressure range (DPR) were not fully evaluated for their associations with hospital admissions for PE. Study subjects comprised cases of 1,148 PE treated at institutions belonging to the Tokyo Cardiovascular Care Unit Network from January 2005 to December 2012. Patient data were combined with a variety of daily local climate parameters obtained from the Japan Meteorological Agency. Every 1°C increase in the DTR at lag0 corresponded to an increased relative risk of hospital admission for PE (odds ratio [OR] 1.036, 95% confidence interval [CI] 1.003 to 1.070). In the cooler season (November to April), an increase of 1 hPa (barometric pressure) in the DPR at lag4 and lag5 was associated with an increased relative risk of hospital admission for PE (OR 1.042, 95% CI 1.007 to 1.077 and OR 0.952, 95% CI 0.914 to 0.992, respectively). An increase in the PE hospitalization rate was seen only in the cool season. Using a metropolitan database, we showed that DTR and DPR have different impacts on hospital admissions for PE. In conclusion, we found that an increase in the DTR increases the PE hospitalization rate, especially during the cooler season. The impact of DTR and DPR on PE incidence and related hospitalizations needs to be further evaluated.

Coarse Particulate Air Pollution Associated with Increased Risk of Hospital Admissions for Respiratory Diseases in a Tropical City, Kaohsiung, Taiwan.

This study was undertaken to determine whether there was an association between coarse particles (PM2.5–10) levels and frequency of hospital admissions for respiratory diseases (RD) in Kaohsiung, Taiwan. Hospital admissions for RD including chronic obstructive pulmonary disease (COPD), asthma, and pneumonia, and ambient air pollution data levels for Kaohsiung were obtained for the period from 2006 to 2010. The relative risk of hospital admissions for RD was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single pollutant model (without adjustment for other pollutants), increased rate of admissions for RD were significantly associated with higher coarse PM levels only on cool days (<25 °C), with a 10 µg/m3 elevation in PM2.5–10 concentrations associated with a 3% (95% CI = 1%–5%) rise in COPD admissions, 4% (95% CI = 1%–7%) increase in asthma admissions, and 3% (95% CI = 2%–4%) rise in pneumonia admissions. No significant associations were found between coarse particle levels and the number of hospital admissions for RD on warm days. In the two-pollutant models, PM2.5–10 levels remained significantly correlated with higher rate of RD admissions even controlling for sulfur dioxide, nitrogen dioxide, carbon monoxide, or ozone on cool days. This study provides evidence that higher levels of PM2.5–10 enhance the risk of hospital admissions for RD on cool days.

Short-Term Effects of Coarse Particulate Matter on Hospital Admissions for Cardiovascular Diseases: A Case-Crossover Study in a Tropical City

This study was undertaken to determine whether there was an association between coarse particles (PM2.5-10) levels and frequency of hospital admissions for cardiovascular diseases (CVD) in Kaohsiung, Taiwan. Hospital admissions for CVD, including ischemic heart disease (IHD), stroke, congestive heart failure (CHF), and arrhythmias, and ambient air pollution data levels for Kaohsiung were obtained for the period 2006–2010. The relative risk of hospital admissions for CVD was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), increased rates of admissions for CVD were significantly associated with higher coarse PM levels only on cool days (< 25°C), with a 10-μg/m3 elevation in PM2.5-10 concentrations associated with a 3% (95% CI = 2–4%) rise in IHD admissions, 5% (95% CI = 4–6%) increase in stroke admissions, 3% (95% CI = 1–6%) elevation in CHF admissions, and 3% (95% CI = 0–6%) rise in arrhythmias admissions. No significant associations were found between coarse particle levels and number of hospital admissions for CVD on warm days. In the two-pollutant models, PM2.5-10 levels remained significantly correlated with higher rate of CVD admissions even controlling for sulfur dioxide, nitrogen dioxide, carbon monoxide, or ozone on cool days. Compared to the effect estimate associated with a 10-μg/m3 increase in PM2.5 levels, effect estimates of frequency of CVD-related admissions associated with a 10-μg/m3 rise in coarse PM levels were weaker. This study provides evidence that higher levels of PM2.5-10 enhance the risk of hospital admissions for CVD.

Effects Of Wildfire Smoke On Community Population Health In The Western Us

Introduction: Wildfires may be a hazard to human health due to the high levels of airborne particulate matter (PM) released from wildfire smoke. However, the health effects of wildfire-emitted fine particles are not well understood and most of the current studies on wildfire and health are based on single wildfire episode. Further, wildfires are anticipated to increase under climate change. This study uses large-scale wildfire smoke data over six years to estimate the health effect of PM specifically from wildfire smoke in the Western US. Methods: We estimated daily PM2.5 concentrations from wildfires (2004-2009) for every county in the Western US (561 counties) using outputs from the state-of-science GEOS-Chem (v9-01-03) global chemical transport model that utilized daily emissions from the Global Fire Emissions Database (GFED3). We demonstrated spatial exposure patterns in an interactive map. The wildfire-specific PM2.5 data were linked to the Medicare data (=65y) in 122 most populated Western US counties. We used a generalized linear mixed model to estimate the relative risk of hospital admissions on days with high wildfire-specific PM compared to matched comparison days for respiratory and cardiovascular admissions. Results: We estimate that about 57 million people were exposed to wildfire smoke between 2004 and 2009 in the Western US, among which 12% are =64 years. Among the Medicare population, respiratory hospital admissions increased 5.0% on days with wildfire smoke (95% CI: 0.91%-9.26%) compared to non-fire days. Cardiovascular hospital admissions did not show significant association with wildfire smoke. Conclusion: This multi-year, multi-county study is the most comprehensive study to date on wildfire smoke and public health in North America. Results indicate health impacts of PM2.5 from wildfires in elderly population in the Western US. The results provide policy reference on establishing or modifying public health programs in susceptible regions.

Short-Term Effects of Fine Particulate Air Pollution on Hospital Admissions for Cardiovascular Diseases: A Case-Crossover Study in a Tropical City

This study was undertaken to determine whether there was an association between fine particles (PM2.5) levels and hospital admissions for cardiovascular diseases (CVD) in Kaohsiung, Taiwan. Hospital admissions for CVD (including ischemic heart disease [IHD], stroke, congestive heart failure [CHF], and arrhythmias) and ambient air pollution data for Kaohsiung were obtained for the period from 2006–2010. The relative risk of hospital admissions for CVD was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), elevated number of admissions for CVD were significantly associated with higher PM2.5 levels only on cool days (<25°C), with an interquartile range rise associated with a 47% (95% CI = 39–56%), 48% (95% CI = 40–56%), 47% (95% CI = 34–61%), and 51% (95% CI = 34–70%) increase in IHD, stroke, CHF, and arrhythmias admissions, respectively. No significant associations between PM2.5 and hospital admissions for CVD were observed on warm days. In the two-pollutant models, PM2.5 levels remained significant even controlling for sulfur dioxide, nitrogen dioxide, carbon monoxide, or ozone on cool days. This study provides evidence that higher levels of PM2.5 enhance the risk of hospital admissions for CVD in Kaohsiung, Taiwan.

Trajectories of risk after hospitalization for heart failure, acute myocardial infarction, or pneumonia: retrospective cohort study

Objective To characterize the absolute risks for older patients of readmission to hospital and death in the year after hospitalization for heart failure, acute myocardial infarction, or pneumonia.Design Retrospective cohort...

Short-Term Effects of Fine Particulate Air Pollution on Ischemic Stroke Occurrence: a Case-Crossover Study

This study was undertaken to determine whether there was a correlation between fine particles (PM2.5) levels and hospital admissions for ischemic stroke (IS) in Taipei, Taiwan. Hospital admissions for IS and ambient air pollution data for Taipei were obtained for the period from 2006-2010. The relative risk of hospital admissions was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), increased admissions for IS were significantly associated with higher levels of PM2.5 on both warm days (&gt;23°C) and cool days (&lt;23°C), with an interquartile range rise associated with a 11% (95% CI = 8-14%) and 4% (95% CI = 2-7%) elevation in admissions for IS, respectively. In the two-pollutant models, PM2.5 remained significantly increased after inclusion of sulfur dioxide (SO2) or ozone (O3) on both warm and cool days. This study provides evidence that higher levels of PM2.5 enhance the risk of hospital admissions for IS.

Hospital admissions for unintentional poisoning in preschool children in England; 2000–2011

We conducted a population based time-trend analysis of all unplanned admissions to National Health Service hospitals for poisoning in preschool children (aged <5 years) in England, between 2000 and 2011....

Relationship Between Hemorrhagic Stroke Hospitalization and Exposure to Fine Particulate Air Pollution in Taipei, Taiwan

This study was undertaken to determine whether there was a correlation between fine particle (PM2.5) levels and hospital admissions for hemorrhagic stroke (HS) in Taipei, Taiwan. Hospital admissions for HS and ambient air pollution data for Taipei were obtained for the period 2006–2010. The relative risk of hospital admissions was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), increased HS admissions were significantly associated with PM2.5 levels both on warm days (>23°C) and cool days (<23°C), with an interquartile range rise associated with a 12% (95% CI = 7–18%) and 4% (95% CI = 0–8%) elevation in admissions for HS, respectively. In the two-pollutant models, PM2.5 remained significantly high after inclusion of SO2 or O3 on both warm and cool days. This study provides evidence that higher levels of PM2.5 increase the risk of hospital admissions for HS.

Fine Particulate Air Pollution and Hospital Admissions for Asthma: A Case-Crossover Study in Taipei

This study was undertaken to determine whether there was a correlation between fine particles (PM2.5) levels and hospital admissions for asthma in Taipei, Taiwan. Hospital admissions for asthma and ambient air pollution data for Taipei were obtained for the period of 2006–2010. The relative risk of hospital admissions for asthma was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), increased asthma admissions were significantly associated with PM2.5 levels both on warm days (>23°C) and cool days (<23°C), with an interquartile range rise associated with a 12% (95% CI = 6–18%) and 3% (95% CI = 0–8%) elevation in admissions for asthma, respectively. In the two-pollutant models, PM2.5 levels remained significant for increased asthma admissions after inclusion of SO2 or O3 both on warm and cool days. This study provides evidence that higher levels of PM2.5 elevate the risk of hospital admissions for asthma in Taiwan.

Fine Particulate Air Pollution and Hospital Admissions for Pneumonia in a Subtropical City: Taipei, Taiwan

This study was undertaken to determine whether there was a correlation between fine particles (PM2.5) levels and hospital admissions for pneumonia in Taipei, Taiwan. Hospital admissions for pneumonia and ambient air pollution data for Taipei were obtained for the period from 2006 to 2010. The relative risk of hospital admissions for pneumonia was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. For the single-pollutant model (without adjustment for other pollutants), increased numbers of admissions for pneumonia were significantly associated with higher PM2.5 levels both on warm days (>23°C) and on cool days (<23°C). This was accompanied by an interquartile range elevation correlated with a 12% (95% CI = 16%–13%) and 4% (95% CI = 3%–6%) rise in number of admissions for pneumonia, respectively. In the two-pollutant models, PM2.5 remained significant after inclusion of sulfur dioxide (SO2) or ozone (O3) both on warm and on cool days. This study provides evidence that higher levels of PM2.5 increase the risk of hospital admissions for pneumonia.