Xiaochuan Pan

Ambient temperature and morbidity: a review of epidemiological evidence.

Objective: In this paper, we review the epidemiological evidence on the relationship between ambient temperature and morbidity. We assessed the methodological issues in previous studies and proposed future research directions. Data sources and data extraction: We searched the PubMed database for epidemiological studies on ambient temperature and morbidity of noncommunicable diseases published in refereed English journals before 30 June 2010. Forty relevant studies were identified. Of these, 24 examined the relationship between ambient temperature and morbidity, 15 investigated the short-term effects of heat wave on morbidity, and 1 assessed both temperature and heat wave effects. Data synthesis: Descriptive and time-series studies were the two main research designs used to investigate the temperature–morbidity relationship. Measurements of temperature exposure and health outcomes used in these studies differed widely. The majority of studies reported a significant relationship between ambient temperature and total or cause-specific morbidities. However, there were some inconsistencies in the direction and magnitude of nonlinear lag effects. The lag effect of hot temperature on morbidity was shorter (several days) compared with that of cold temperature (up to a few weeks). The temperature–morbidity relationship may be confounded or modified by sociodemographic factors and air pollution. Conclusions: There is a significant short-term effect of ambient temperature on total and cause-specific morbidities. However, further research is needed to determine an appropriate temperature measure, consider a diverse range of morbidities, and to use consistent methodology to make different studies more comparable.

The impact of temperature on mortality in Tianjin, China: a case-crossover design with a distributed lag nonlinear model.

Background: Although interest in assessing the impacts of temperature on mortality has increased, few studies have used a case-crossover design to examine nonlinear and distributed lag effects of temperature on mortality. Additionally, little evidence is available on the temperature–mortality relationship in China or on what temperature measure is the best predictor of mortality. Objectives: Our objectives were to use a distributed lag nonlinear model (DLNM) as a part of case-crossover design to examine the nonlinear and distributed lag effects of temperature on mortality in Tianjin, China and to explore which temperature measure is the best predictor of mortality. Methods: We applied the DLNM to a case-crossover design to assess the nonlinear and delayed effects of temperatures (maximum, mean, and minimum) on deaths (nonaccidental, cardiopulmonary, cardiovascular, and respiratory). Results: A U-shaped relationship was found consistently between temperature and mortality. Cold effects (i.e., significantly increased mortality associated with low temperatures) were delayed by 3 days and persisted for 10 days. Hot effects (i.e., significantly increased mortality associated with high temperatures) were acute and lasted for 3 days and were followed by mortality displacement for nonaccidental, cardiopulmonary, and cardiovascular deaths. Mean temperature was a better predictor of mortality (based on model fit) than maximum or minimum temperature. Conclusions: In Tianjin, extreme cold and hot temperatures increased the risk of mortality. The effects of cold last longer than the effects of heat. Combining the DLNM and the case-crossover design allows the case-crossover design to flexibly estimate the nonlinear and delayed effects of temperature (or air pollution) while controlling for season.

Global variation in the effects of ambient temperature on mortality: a systematic evaluation

Background: Studies have examined the effects of temperature on mortality in a single city, country, or region. However, less evidence is available on the variation in the associations between temperature and mortality in multiple countries, analyzed simultaneously. Methods: We obtained daily data on temperature and mortality in 306 communities from 12 countries/regions (Australia, Brazil, Thailand, China, Taiwan, Korea, Japan, Italy, Spain, United Kingdom, United States, and Canada). Two-stage analyses were used to assess the nonlinear and delayed relation between temperature and mortality. In the first stage, a Poisson regression allowing overdispersion with distributed lag nonlinear model was used to estimate the community-specific temperature-mortality relation. In the second stage, a multivariate meta-analysis was used to pool the nonlinear and delayed effects of ambient temperature at the national level, in each country. Results: The temperatures associated with the lowest mortality were around the 75th percentile of temperature in all the countries/regions, ranging from 66th (Taiwan) to 80th (UK) percentiles. The estimated effects of cold and hot temperatures on mortality varied by community and country. Meta-analysis results show that both cold and hot temperatures increased the risk of mortality in all the countries/regions. Cold effects were delayed and lasted for many days, whereas heat effects appeared quickly and did not last long. Conclusions: People have some ability to adapt to their local climate type, but both cold and hot temperatures are still associated with increased risk of mortality. Public health strategies to alleviate the impact of ambient temperatures are important, in particular in the context of climate change.

The association between fine particulate air pollution and hospital emergency room visits for cardiovascular diseases in Beijing, China

BACKGROUND Because epidemiological studies have yielded different results, the association between exposure to fine particulate matter less than 2.5 microm in aerodynamic diameter (PM(2.5)) and acute events of cardiovascular diseases (CVD) is unknown. Additionally, no research has been conducted to explore the association between PM(2.5) and hospital emergency room (ER) visits of cardiovascular diseases in Beijing, China. OBJECTIVE To explore the association between PM(2.5) and the hospital ER visits in Beijing, China for CVD {(International Classification of Diseases, 10th vision (ICD-10): I00-I99)}. METHODS We collected data for daily hospital ER visits for CVD from the Peking University Third Hospital, daily ambient PM(2.5) data from a fixed monitor site at Peking University, and data on the daily level of gaseous air pollutants {sulfur dioxide (SO(2)) and nitrogen dioxide (NO(2))} from the Beijing Municipal Environmental Monitoring Center between June 1, 2004 and December 31, 2006. A time-stratified case-crossover design was used to evaluate associations between CVD health outcomes and ambient air pollutants. RESULTS 8377 hospital ER visits of CVD were collected in our study. After adjusting the temperature and the relative humidity, the associations for 10 microg/m(3) increases in levels of PM(2.5), SO(2), or NO(2) and hospital ER visits for cardiovascular diseases were statistically significant with odds ratios (ORs) of 1.005{95% confidence interval (CI): 1.001-1.009}, 1.014(95% CI: 1.004-1.024), and 1.016(95% CI: 1.003-1.029), respectively. CONCLUSION These findings suggest that elevated levels of ambient air pollutants are associated with the increase in hospital ER visits for CVD in Beijing, China.

The burden of air pollution on years of life lost in Beijing, China, 2004-08: retrospective regression analysis of daily deaths

Objectives To better understand the burden of air pollution on deaths, we examined the effects of air pollutants on years of life lost (YLL) in Beijing, China. Design Retrospective regression analysis using daily time series. Setting 8 urban districts in Beijing, China. Participants 80 515 deaths (48 802 male, 31 713 female) recorded by the Beijing death classification system during 2004-08. Main outcome measures Associations between daily YLL and ambient air pollutants (particulate matter with aerodynamic diameter <2.5 µm (PM2.5), PM10, SO2, and NO2), after adjusting for long term trends, seasonality, day of the week, and weather conditions. We also examined mortality risk related to air pollutants. Results Mean concentrations of daily PM2.5, PM10, SO2 and NO2 were 105.1 μg/m3, 144.6 μg/m3, 48.6 μg/m3, and 64.2 μg/m3, respectively. All air pollutants had significant effects on years of life lost when we used single pollutant models. An interquartile range (IQR) increase in PM2.5, PM10, SO2, and NO2 was related to YLL increases of 15.8, 15.8, 16.2, and 15.1 years, respectively. The effects of air pollutants on YLL appeared acutely and lasted for two days (lag 0-1); these effects associated with an IQR increase in PM2.5 were greater in women than men (11.1 (95% confidence interval 4.7 to 17.5) v 4.7 (−2.9 to 12.3) YLL) and in people aged up to 65 years than those older than 65 years (12.0 (2.9 to 21) v 3.8 (−0.9 to 8.6) YLL). The mortality risk associated with an IQR increase in PM2.5 was greater for people older than 65 years (2.5% (95% confidence interval 0.6% to 4.5%) increase of mortality) than those aged up to 65 years (0.7% (−0.8% to 2.2%)). Conclusions YLL provides a complementary measure for examining the effect of air pollutants on mortality. Increased YLL are associated with increased air pollution. This study highlights the need to reduce air pollution in Beijing, China, to protect the health of the population.

Exposures to Particulate Matter and Polycyclic Aromatic Hydrocarbons and Oxidative Stress in Schoolchildren

Background Air pollution is known to contribute to respiratory and cardiovascular mortality and morbidity. Oxidative stress has been suggested as one of the main mechanisms for these effects on health. Objective The aim of this study was to analyze the effects of exposure to particulate matter (PM) with aerodynamic diameters ≤ 10 μm (PM10) and ≤ 2.5 μm (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) on urinary malondialdehyde (MDA) levels in schoolchildren. Methods The study population consisted of 120 schoolchildren. The survey and measurements were conducted in four cities—two in China (Ala Shan and Beijing) and two in Korea (Jeju and Seoul)—between 4 and 9 June 2007. We measured daily ambient levels of PM and their metal components at the selected schools during the study period. We also measured urinary 1-hydroxypyrene (1-OHP) and 2-naphthol, to assess PAH exposure, and MDA, to assess oxidative stress. Measurements were conducted once a day for 5 consecutive days. We constructed a linear mixed model after adjusting for individual variables to estimate the effects of PM and PAH on oxidative stress. Results We found statistically significant increases in urinary MDA levels with ambient PM concentrations from the current day to the 2 previous days (p < 0.0001). Urinary 1-OHP level also showed a positive association with urinary MDA level, which was statistically significant with or without PM in the model (p < 0.05). Outdoor PM and urinary 1-OHP were synergistically associated with urinary MDA levels. Some metals bound to PM10 (aluminum, iron, strontium, magnesium, silicon, arsenic, barium, zinc, copper, and cadmium) and PM2.5 (magnesium, iron, strontium, arsenic, cadmium, zinc, aluminum, mercury, barium, and copper) also had significant associations with urinary MDA level. Conclusion Exposure to PM air pollution and PAHs was associated with oxidative stress in schoolchildren.

Ambient temperature and mortality: an international study in four capital cities of East Asia.

Extreme ambient temperature has been associated with increased daily mortality across the world. We describe the ambient temperature-mortality association for four capital cities in East Asia, Seoul, Beijing, Tokyo, and Taipei, and identify a threshold temperature for each city and the percent increase in mortality. We adapted generalized linear modeling with natural cubic splines (GLM+NS) to examine the association between daily mean apparent temperature (AT) and total mortality, as well as mortality due to respiratory (RD) and cardiovascular (CVD) causes in a threshold model. We conducted a time-series analysis adjusting for day of the week and long-term time trend. The study period differed by city. The threshold temperature for all seasons was estimated to be 30.1-33.5 degrees C, 31.3-32.3 degrees C, 29.4-30.8 degrees C, and 25.2 degrees -31.5 degrees C for Seoul, Beijing, Tokyo, and Taipei, respectively, on the same day. For the mean daily AT increase of 1 degrees C above the thresholds in Seoul, Tokyo, and Taipei, estimated percentage increases in daily total mortality were 2.7 (95% confidence interval (CI)=2.2-3.1), 1.7 (95% CI=1.5-2.0), and 4.3 (95% CI=2.9-5.7), respectively. Beijing provided no total mortality counts. Estimated percentage increases were 2.7-10.5 for RD mortality, 1.1-9.3 for CVD mortality in 4 cities. This study identified increased mortality due to exposure to elevated AT. The importance of effects of AT and city-specific threshold temperatures suggests that analyses of the impact of climate change should take regional differences into consideration.

The relationship between particulate air pollution and emergency hospital visits for hypertension in Beijing, China.

BACKGROUND A number of epidemiological studies have examined the adverse effect of air pollution on mortality and morbidity. Also, several studies have investigated the associations between air pollution and specific-cause diseases including arrhythmia, myocardial infarction, and heart failure. However, little is known about the relationship between air pollution and the onset of hypertension. OBJECTIVE To explore the risk effect of particulate matter air pollution on the emergency hospital visits (EHVs) for hypertension in Beijing, China. METHODS We gathered data on daily EHVs for hypertension, fine particulate matter less than 2.5 microm in aerodynamic diameter (PM(2.5)), particulate matter less than 10 microm in aerodynamic diameter (PM(10)), sulfur dioxide, and nitrogen dioxide in Beijing, China during 2007. A time-stratified case-crossover design with distributed lag model was used to evaluate associations between ambient air pollutants and hypertension. Daily mean temperature and relative humidity were controlled in all models. RESULTS There were 1,491 EHVs for hypertension during the study period. In single pollutant models, an increase in 10 microg/m(3) in PM(2.5) and PM(10) was associated with EHVs for hypertension with odds ratios (overall effect of five days) of 1.084 (95% confidence interval (CI): 1.028, 1.139) and 1.060% (95% CI: 1.020, 1.101), respectively. CONCLUSION Elevated levels of ambient particulate matters are associated with an increase in EHVs for hypertension in Beijing, China.

Extremely cold and hot temperatures increase the risk of ischaemic heart disease mortality: epidemiological evidence from China

Objective To examine the effects of extremely cold and hot temperatures on ischaemic heart disease (IHD) mortality in five cities (Beijing, Tianjin, Shanghai, Wuhan and Guangzhou) in China; and to examine the time relationships between cold and hot temperatures and IHD mortality for each city. Design A negative binomial regression model combined with a distributed lag non-linear model was used to examine city-specific temperature effects on IHD mortality up to 20 lag days. A meta-analysis was used to pool the cold effects and hot effects across the five cities. Patients 16 559 IHD deaths were monitored by a sentinel surveillance system in five cities during 2004–2008. Results The relationships between temperature and IHD mortality were non-linear in all five cities. The minimum-mortality temperatures in northern cities were lower than in southern cities. In Beijing, Tianjin and Guangzhou, the effects of extremely cold temperatures were delayed, while Shanghai and Wuhan had immediate cold effects. The effects of extremely hot temperatures appeared immediately in all the cities except Wuhan. Meta-analysis showed that IHD mortality increased 48% at the 1st percentile of temperature (extremely cold temperature) compared with the 10th percentile, while IHD mortality increased 18% at the 99th percentile of temperature (extremely hot temperature) compared with the 90th percentile. Conclusions Results indicate that both extremely cold and hot temperatures increase IHD mortality in China. Each city has its characteristics of heat effects on IHD mortality. The policy for response to climate change should consider local climate–IHD mortality relationships.

Asian Dust Storm and pulmonary function of school children in Seoul

Health effects of the Asian Dust Storm (ADS) have not been evaluated adequately, even though it may affect health of people in East Asia. This study was conducted to evaluate whether the ADS affects particulate air pollution and pulmonary function of children. We studied 110 school children in Seoul, Korea with daily measurement of peak expiratory flow rate (PEFR) from May 13 to June 15, 2007. PM(2.5), PM(10) and metals bound to the particles were also determined daily during the study period in Ala Shan and Beijing (China) as well as in Seoul (Korea). Three-day back trajectories showed that air parcels arrived at Seoul mostly from the desert areas in China and Mongolia through eastern China during ADS event affecting levels of particulate pollutants in the areas. Analysis of metals bound to the particulates showed that natural metal levels were much higher than the anthropogenic metal levels. We found that ambient concentrations of PM(2.5) and PM(10) were not significantly associated with PEFR in school children except asthmatics during the study period (P>0.05). However, most of the metal concentrations bound to the particulates were significantly associated with decrease of the childrens PEFR (P<0.05). The effect of anthropogenic metals was not different from natural components of metals for reduction of PEFR. This result indicates that exposure to the metals bound to particles during the ADS period reduces childrens pulmonary function, but there was no difference of potency for reduction of the pulmonary function between natural and anthropogenic metal components.