Chih-g Chen

Statin Use and the Risk of Liver Cancer: A Population-Based Case - Control Study

OBJECTIVES:Experimental studies have shown that statins have potential protective effects against cancer. The aim of this study was to investigate whether the use of statins was associated with liver cancer risk.METHODS:We conducted a population-based case–control study in Taiwan. Data were retrospectively collected from the Taiwan National Health Insurance Research Database. Cases consisted of all patients who were aged ≥50 years and had a first-time diagnosis of liver cancer for the period between 2005 and 2008. Controls were pair matched to cases by age, sex, and index date. Adjusted odds ratios (ORs) and 95% CIs (95% confidence intervals) were estimated using multiple logistic regression.RESULTS:We examined 1,166 liver cancer cases and 1,166 controls. Compared with the group with no use of statins, the adjusted ORs were 0.62 (95% CI=0.42–0.91) for the group having been prescribed statins below 215.4 defined daily dose (DDD) and 0.63 (95% CI=0.37–1.06) for the group with cumulative statin use ≥215.4 DDD. The ORs for the group with cumulative statin use ≥215.4 DDD were not statistically significant, but this may be due to the relatively small number of subjects.CONCLUSIONS:The results of this study suggest that statins may reduce the risk of liver cancer.

Effects of Asian Dust Storm Events on Hospital Admissions for Congestive Heart Failure in Taipei, Taiwan

In spring, windblown dust storms originating in the deserts of Mongolia and China make their way to Taipei city. These occurrences are known as Asian dust storm (ADS) events. These ADS events lead to enhanced PM10 levels over those generated by the usual local sources. The objective of this study was to assess the possible associations of PM10 with hospital admissions for congestive heart failure (CHF) in Taipei, Taiwan, during the period from 1996 to 2001. Fifty-four dust storm episodes, which were classified as index days, were identified. Daily CHF admissions on index days were compared with admissions on comparison days. Two comparison days were selected for each index day, 7 d before the index days and 7 d after the index days. The effects of ADS on hospital admissions for CHF were prominent 1 d after the event (relative risku2009=u20091.114; 95% confidence intervalu2009=u20090.993–1.250). However, the association was not statistically significant. There may not have been enough power to detect associations resulting from the inadequate sample size of CHF admissions on ADS events days. However, it seems worthwhile to pay more attention to the ADS events and health in the future.

Air Pollution and Hospital Admissions for Asthma in a Subtropical City: Taipei, Taiwan

This study was undertaken to determine whether there is an association between exposure to air pollutants levels and number of hospital admissions for asthma in Taipei, Taiwan. Hospital admissions for asthma and ambient air pollution data for Taipei were obtained for the period from 1996 through 2003. The relative risk of hospital admission for asthma was estimated using a case-crossover approach, controlling for weather variables, day of the week, seasonality, and long-term time trends. In the single-air-pollutant model, on warm days (≥25°C) statistically significant positive associations were found for SO2, NO2, and CO levels with an increase in asthmatic admissions. On cool days (<25°C), all air pollutants were significantly associated with elevated asthma admissions except SO2. For the two-air-pollutant model, CO significantly increases hospital admissions for asthma in combination with each of the other four pollutants on warm days. On cool days, NO2 and O3 significantly elevated asthma rates in all the two-air-pollutant models. This study provides evidence that higher levels of ambient air pollutant concentrations increase the risk of hospital admissions for asthma.

Association of brain cancer with residential exposure to petrochemical air pollution in Taiwan.

To investigate the relationship between petrochemical air pollution and brain cancer (29 yr of age or younger), the authors conducted a matched case-control study using deaths that occurred in Taiwan from 1995 through 2005. Data on all eligible brain cancer deaths were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of subjects who died from causes other than neoplasms or diseases that were not associated with respiratory problems. The controls were pair matched to the cases by sex, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. The proportion of a municipalitys total population employed in the petrochemical industry in a municipality was used as an indicator of a residents exposure to air emissions from the petrochemical industry. The subjects were divided into tertiles according to the levels of the index just described. Subjects who lived in the group of municipalities characterized by the highest levels of petrochemical air pollution had a statistically significant higher risk of developing brain cancer than the group that lived in municipalities with the lowest petrochemical air pollution levels after controlling for possible confounders (ORu2009=u20091.65, 95% CIu2009=u20091.00−2.73). The findings of this study warrant further investigation of the role of petrochemical air pollution in the etiology of brain cancer.

Childhood Leukemia Development and Correlation with Traffic Air Pollution in Taiwan using Nitrogen Dioxide as an Air Pollutant Marker

To investigate the relationship between traffic air pollution and development of childhood leukemia (14 yr of age or younger), studies were conducted on a matched cancer case-control cohort using childhood deaths that occurred in Taiwan from 1995 through 2005. Data on all eligible childhood leukemia deaths were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of children who died from causes other than neoplasms or from diseases that were not associated with respiratory complications. The controls were pair matched to the cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Air quality data for recorded concentrations of nitrogen dioxide (NO2) from study municipalities for 1995–2005 were obtained as an indicator of a subjects exposure to air emissions from motor vehicles. The subjects were divided into tertiles according to the levels of NO2 in their residential municipality. The results showed that there was a significant exposure-response relationship between exposure to traffic exhaust pollutants and the risk of leukemia among young children after controlling for possible confounders. The findings of this study warrant further investigation of the role of traffic air pollution in the etiology of childhood leukemia.

TRIHALOMETHANES IN DRINKING WATER AND THE RISK OF DEATH FROM KIDNEY CANCER: DOES HARDNESS IN DRINKING WATER MATTER?

The objectives of this study were to (1) examine the relationship between total trihalomethanes (TTHM) levels in public water supplies and risk of development of kidney cancer and (2) determine whether hardness levels in drinking water modify the effects of TTHM on risk of kidney cancer induction. A matched case-control study was used to investigate the relationship between the risk of death attributed to kidney cancer and exposure to TTHM in drinking water in 53 municipalities in Taiwan. All kidney cancer deaths in the 53 municipalities from 1998 through 2007 were obtained. Controls were deaths from other causes and were pair-matched to the cancer cases by gender, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each cancer case. Data on TTHM levels and levels of hardness in drinking water were also collected. The municipality of residence for cancer cases and controls was presumed to be the source of the subjects TTHM and hardness exposure via drinking water. Relative to individuals whose TTHM exposure level was <4.9 ppb, the adjusted OR (95% CI) for kidney cancer was 0.98 (0.77–1.25) for individuals who resided in municipalities served by drinking water with a TTHM exposure ≥4.9 ppb. However, evidence of an interaction was noted between the use of soft water and drinking water TTHM concentrations. Increased knowledge of the interaction between hardness and TTHM levels in reducing risk of kidney cancer development will aid in public policy decision and establishing standards to prevent disease occurrence.

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.

Short-Term Effect of Fine Particulate Air Pollution on Daily Mortality: A Case-Crossover Study in a Tropical City, Kaohsiung, Taiwan

Many studies have examined the short-term effects of air pollution on frequency of daily mortality over the past two decades. However, information on the relationship between levels of fine particles (PM2.5) and daily mortality is relatively sparse due to limited availability of monitoring data. Further the results are inconsistent. This study was undertaken to determine whether there was an association between PM2.5 levels and daily mortality rate in Kaohsiung, Taiwan, a large industrial city with a tropical climate. Daily mortality rate, air pollution parameters, and weather data for Kaohsiung were obtained for the period from 2006 through 2008. The relative risk of daily mortality occurrence was estimated using a time-stratified case-crossover approach, controlling for (1) weather variables, (2) day of the week, (3) seasonality, and (4) long-term time trends. For the single-pollutant model (without adjustment for other pollutants), no significant effects were found between PM2.5 and frequency of daily mortality on warm days (≥25°C). On cool days, PM2.5 showed significant correlation with increased risk of mortality rate for all causes and circulatory diseases in single-pollutant model. There was no indication of an association between PM2.5 and deaths due to respiratory diseases. The relationship appeared to be stronger on cool days. This study provided evidence of associations between short-term exposure to PM2.5 and elevated risk of death for all cause and circulatory diseases.

Air Pollution and Postneonatal Mortality in a Tropical City: Kaohsiung, Taiwan

With growing evidence of the association between daily mortality and air pollution in adults, it is important to investigate whether infants are also susceptible to the adverse health effects of ambient air pollutants. The purpose of this study is to examine the relationship between air pollution and postneonatal mortality in Kaohsiung, Taiwan, a large industrial city with a tropical climate, during the period 1994–2000, using a case-crossover analysis. Case–crossover analysis provides an alternative to Poisson time-series regression for studying the short-term adverse health effects of air pollution. The air pollutants examined included particulate matter (PM10), sulfur dioxide (SO2), ozone (O3), nitrogen dioxide (NO2), and carbon monoxide (CO). The risk of postneonatal deaths was estimated to increase by 4.0% per 67 μg/m3 (the interquartile range in daily ambient concentration of PM10) for PM10, 1.8% per 17.84 ppb for NO2, 5.1% per 0.31 ppm for CO, and 4.6% per 19.20 ppb for O3. Although positive, none of these associations achieved statistical significance. The established link between air pollution levels and infant mortality may not be as strong in cities with tropical climates, although other factors such as differences in pollutant mix or the underlying health of the postneonates may explain the lack of a strong association in this study. Further studies of this type in cities with varying climates and cultures are needed.

Ambient Exposure to Criteria Air Pollutants and Risk of Death from Bladder Cancer in Taiwan

To investigate the relationship between air pollution and risk of death from bladder cancer, the authors conducted a matched case-control study using deaths that occurred in Taiwan from 1995 through 2005. Data on all eligible bladder cancer deaths were obtained from the Bureau of Vital Statistics of the Taiwan Provincial Department of Health. The control group consisted of people who died from causes other than cancer or diseases associated with genitourinary problems. The controls were pair matched to the cases by sex, year of birth, and year of death. Each matched control was selected randomly from the set of possible controls for each case. Classification of exposure to municipality air pollution was based on the measured levels of nitrogen dioxide and sulfur dioxide. The results of the present study show that there is a significant positive association between the levels of air pollution and bladder cancer mortality. The adjusted odds ratios (95% confidence interval) were 1.37 (1.03–1.82) for the group with medium air pollution level and 1.98 (1.36–2.88) for the group with high air pollution level when compared to the group with the low air pollution level. Trend analyses showed statistically significant trend in risk of death from bladder cancer with increasing air pollution level. The findings of this study warrant further investigation of the role of air pollutants in the etiology of bladder cancer.