Jong Tae Lee

Air Pollution A New Risk Factor in Ischemic Stroke Mortality

Background and Purpose— Air pollution is known to be associated with cardiovascular disease, but little is known about the occurrence of stroke in relation to air pollution. We investigated the association between acute stroke mortality and air pollution over a 7-year period (January 1991 through December 1997) in Seoul, Korea. Methods— A generalized additive model was used to regress daily stroke death counts for each air pollutant, controlling for time trends, day of the week, and meteorological influences such as temperature, relative humidity, and atmospheric pressure. Ischemic and hemorrhagic stroke deaths were examined separately. Results— The effects of air pollutants on ischemic stroke mortality were statistically significant, whereas this was not the case for hemorrhagic stroke mortality. We observed estimated relative risks of 1.03 (95% CI, 1.00 to 1.06) and 1.04 (95% CI, 1.01 to 1.08) for ischemic stroke mortality for each interquartile range increase in total suspended particulates and sulfur dioxide concentrations on the same day. We also found significantly increased relative risks of 1.04 (95% CI, 1.01 to 1.07) for nitrogen dioxide with a 1-day lag, of 1.06 (95% CI, 1.02 to 1.09) for carbon monoxide with a 1-day lag, and of 1.06 (95% CI, 1.02 to 1.10) for ozone with a 3-day lag for each interquartile range increase. Conclusions— These findings indicate that air pollutants are significantly associated with ischemic stroke mortality, which suggests an acute pathogenetic process in the cerebrovascular system induced by air pollution.

Ischemic stroke associated with decrease in temperature

Background Some studies suggest low temperatures can affect mortality, especially deaths associated with circulatory and respiratory conditions. Methods We investigated the association between ischemic stroke onset and decrease in temperature in 545 patients over a 3-year period (January 1998 to December 2000) in Incheon, Korea. We used a case-crossover study design to assess changes in the risk of ischemic stroke during a brief hazard period after exposure to decrease in temperature. For each subject, the case period was matched to 2 control periods exactly 1 week before and after onset of the ischemic stroke. Results Decreased ambient temperature was associated with risk of acute ischemic stroke. The strongest effect was seen on day after exposure to cold weather. The odds ratio (OR) for an interquartile range decrease in temperature was 2.9 (95% confidence interval [CI] = 1.5–5.3). The risk period was 24-48 hours after cold exposure. Risk estimates associated with decreased temperature were greater in the winter than in the summer. Women, persons greater than 65 years of age, nonobese persons, and those with previous hypertension or hypercholesterolemia were more susceptible to cold-induced ischemic stroke. Conclusions These results suggest that stroke occurrence rises with decreasing temperature, and that even a moderate decrease in temperature can increase the risk of ischemic stroke. Susceptible people should take steps to protect themselves from cold, especially in the winter.

Air Pollution and Asthma Among Children in Seoul, Korea

Background. As information about the health risks associated with air pollution has become available, attention has focused increasingly on susceptible persons such as children and persons with preexisting respiratory diseases, such as asthma. Methods. We investigated the association between outdoor air pollution and asthma attacks among children under 15 years of age in Seoul, Korea. We estimated the relative risks of hospitalization associated with an interquartile range (IQR) increase in pollutant concentrations and used time series analysis of the counts by means of the generalized additive Poisson model. Results. The estimated relative risk of hospitalization for asthma was 1.07 (95% confidence interval [CI] = 1.04–1.11) for particulate matters less than or equal to 10 &mgr;m in aerodynamic diameter (IQR = 40.4 &mgr;g/m3); 1.11 (95% CI = 1.06–1.17) for sulfur dioxide (IQR = 4.4 ppb); 1.15 (95% CI = 1.10–1.20) for nitrogen dioxide (IQR = 14.6 ppb); 1.12 (95% CI = 1.07–1.16) for ozone (IQR = 21.7 ppb); and 1.16 (95% CI = 1.10–1.22) for carbon monoxide (IQR = 1.0 ppm). Conclusions. These findings support the hypothesis that air pollution at levels below the current standards of Korea is harmful to sensitive subjects such as asthmatic children.

PM10 and Pregnancy Outcomes : A Hospital-Based Cohort Study of Pregnant Women in Seoul

Objective: The aim of this study was to evaluate the effects of PM10 on birth outcomes using a prospective cohort of pregnant women. Methods: The multicenter prospective study was conducted in Korea from 2001 to 2004. To estimate the effects of PM10 exposure on birth outcomes, the logistic and linear regression model and the generalized additive model for nonlinear relationships were used. Results: Stillbirths were affected by PM10 level during the third trimesters (OR = 1.10, 95% CI = 1.02–1.14), and birth defects were influenced by the PM10 exposure during the second trimesters (OR = 1.16, 95% CI = 1.00–1.34). Intrauterine growth retardation was affected by the first trimesters PM10 exposure. On the other hand, premature birth was affected by the PM10 exposure during the third trimester, and low-birth-weight births were affected by the PM10 level during entire trimesters of pregnancy. Conclusions: PM10 exposure during pregnancy may result in adverse birth outcomes with different critical periods.

Effect of air pollution on asthma-related hospital admissions for children by socioeconomic status associated with area of residence.

The authors evaluated whether the effects of air pollution on asthma in children differed by the regional socioeconomic status (SES) associated with the area in which children resided. They analyzed data on air pollution, asthma-related hospitalization, weather conditions, and SES collected from 25 subregions in Seoul from January 1 to December 31, 2002. The National Health Insurance Cooperation provided data for children aged younger than 15 years who were living in Seoul and hospitalized for asthma-related health conditions (ICD-10 codes J45-J46). Exposure to interquartile range increase of airborne particles ≤ 10 μm in aerodynamic diameter, sulfur dioxide, and nitrogen dioxide in districts associated with a lower SES, the estimated percent increase of hospitalization for asthma among children was 31% (95% confidence interval [CI] = 14%-51%), 29% (95% CI = 8%-53%), and 29% (95% CI = 5%-58%), respectively. This suggests that not only biological sensitivity markers, but also the SES of subjects, should be considered as potentially confounding factors.

Benefits of Mitigated Ambient Air Quality Due to Transportation Control on Childhood Asthma Hospitalization during the 2002 Summer Asian Games in Busan, Korea

Abstract The objective of this study is to see whether there were any health benefits of mitigated air pollution concentration due to reduced traffic flow during a citywide intervention for the 2002 Summer Asian Games. Relative risks of hospitalization for childhood asthma during the post-Asian Game period compared with the baseline period were estimated using a time-series analysis of the generalized additive Poisson model. Fourteen consecutive days of traffic volume control in Busan during the Games reduced all regulated air pollutant levels by 1–25%. The estimated relative risk of hospitalization during the post-Games period over the baseline period was 0.73 (95% confidence interval [CI] = 0.49, 1.11). We observed that this reduced air pollution was unique in 2002 when the traffic volume reduction program was applied during the Games period. This empirical data provides epidemiologic evidence of the health benefits resulting from environmental interventions to reduce ambient air pollution.

Effects of Air Pollution on Postneonatal Infant Mortality Among Firstborn Infants in Seoul, Korea: Case-Crossover and Time-Series Analyses

Infants are known to be susceptible to the adverse health effects of ambient air pollution. The authors examined the relationship between air pollution and postneonatal mortality from all causes among firstborn infants in Seoul, Korea, during 1999-2003, using both case-crossover and time-series analyses. Using a bidirectional control-sampling approach, the authors compared the effects of various types of air pollution on postneonatal mortality. The relative risk of postneonatal mortality from all causes was 1.000 (95% confidence interval [CI] = 0.998-1.002) for particulate matter with a diameter <10 μm, 1.002 (95% CI = 0.994-1.009) for nitrogen dioxide, 1.015 (95% CI = 0.973-1.058) for sulfur dioxide, 1.029 (95% CI = 0.833-1.271) for carbon monoxide, and 0.984 (95% CI = 0.977-0.992) for ozone for each 1-unit increase of air pollution level in the 1:6 control selection scheme. The authors observed a positive association between air pollution and infant daily mortality except for the studied particulate matter and ozone, although it was not statistically significant. They obtained similar results in the time-series analysis. The risk of postneonatal infant death from all causes was positively associated with all studied air pollutants except ozone. The authors also confirmed that the bidirectional method with many controls will give a more efficient estimator than will a method with fewer controls.

Evaluating the Effect of Daily PM10 Variation on Mortality

Many epidemiological studies have shown the association between daily mortality and daily average of PM10 level. Daily average of PM10 has been used for regression type time-series analysis. This article suggests that daily mean mortality is not only a function of daily mean but also a function of daily standard deviation of PM10. We used generalized additive Poisson regression model with overdispersion parameter to investigate this hypothesis using the data from Seoul, Korea, from 1997 to 2001. One interquartile range (IQR = 42.11 μg/m3) increase of daily mean level of PM10 was found to be associated with 2.1% increase of additional daily mortality (RR = 1.021, 95% CI = 1.009–1.035) after controlling for other confounders. Similarly, we also found that one IQR (11.93 μg/m3) increase in daily standard deviation of PM10 is associated with 2.5% increase of additional risk of death (RR = 1.025, 95% CI = 1.000–1.028) when other covariates remained the same. These findings may provide new insight into the possible explanation of health effect of PM10 and support the hypothesis that PM10 deviation is also an important risk factor after controlling for daily mean PM10 level.

Prediction Approaches of Personal Exposure from Ambient Air Pollution Using Spatial Analysis: A Pilot Study Using Ulsan Cohort Data

The objectives of this study were to introduce spatial interpolation methods which have been applied in recent papers, to apply three methods (nearest monitor, inverse distance weighting, kriging) to domestic data (Ulsan cohort) as an example of estimating the personal exposure levels. We predicted the personal exposure estimates of 2,102 participants in Ulsan cohort using spatial interpolation methods based on information of their residential address. We found that there was a similar tendency among the estimates of each method. The correlation coefficients between predictions from pairs of interpolation methods (except for the correlation coefficient between nearest montitor and kriging of CO and ) were generally high (r

A Time-series Study on Relationship between Visibility as an Indicator of Air Pollution and Daily Respiratory Mortality

There seems to be a consensus among most people that visibility impairment is the most obvious indicator of air pollution. While considerable evidence on the association between air pollution and health outcomes including death and disease have been established, based on industrial complex areas or huge urban cities, time-series, case-crossover and cohort studies, scarce literature exists on the direct evidence for the association between visibility and adverse health outcomes. Our study is assessed the effect of air pollution measured by visibility impairment on respiratory mortality over a period of six years. Relative risks in respiratory deaths were estimated by a Poisson regression model of daily deaths between . Daily counts of respiratory deaths as dependent variable was modelled with daily 24-hr mean visibility measurements (kilometers) as independent variable by means of Poisson regression. This model is controlled for confounding factors such as day of weeks, weather variables, seasonal variables and . The results in this study is observed the statistically significant association between an inverse health effect and visibility during the study period for respiratory mortality (percentage change in the relative risk for all aged -0.57%, 95% Cl, ; for aged -7.12%, 95% Cl, ; for 65+ aged -0.43%, 95% Cl, per 1 km increased in visibility). The effect size was much reduced during warm season. Visibility impairment resulting from air pollution is strongly associated with respiratory mortality, especially for children may be spent at outdoor. Our result provides a quick and useful indicator for eliciting the contribution of air pollution to the excess risk of respiratory mortality in Seoul, Korea.