Ping-Yan Chen

Daily temperature and mortality: a study of distributed lag non-linear effect and effect modification in Guangzhou

BackgroundAlthough many studies have documented health effects of ambient temperature, little evidence is available in subtropical or tropical regions, and effect modifiers remain uncertain. We examined the effects of daily mean temperature on mortality and effect modification in the subtropical city of Guangzhou, China.MethodsA Poisson regression model combined with distributed lag non-linear model was applied to assess the non-linear and lag patterns of the association between daily mean temperature and mortality from 2003 to 2007 in Guangzhou. The case-only approach was used to determine whether the effect of temperature was modified by individual characteristics, including sex, age, educational attainment and occupation class.ResultsHot effect was immediate and limited to the first 5 days, with an overall increase of 15.46% (95% confidence interval: 10.05% to 20.87%) in mortality risk comparing the 99th and the 90th percentile temperature. Cold effect persisted for approximately 12 days, with a 20.39% (11.78% to 29.01%) increase in risk comparing the first and the 10th percentile temperature. The effects were especially remarkable for cardiovascular and respiratory mortality. The effects of both hot and cold temperatures were greater among the elderly. Females suffered more from hot-associated mortality than males. We also found significant effect modification by educational attainment and occupation class.ConclusionsThere are significant mortality effects of hot and cold temperatures in Guangzhou. The elderly, females and subjects with low socioeconomic status have been identified as especially vulnerable to the effect of ambient temperatures.

Global climate change: Impact of diurnal temperature range on mortality in Guangzhou, China

Diurnal temperature range (DTR) is an important meteorological indicator associated with global climate change, but little is known about the effects of DTR on mortality. We examined the effects of DTR on cause-/age-/education-specific mortality in Guangzhou, a subtropical city in China during 2003-2010. A quasi-Poisson regression model combined with distributed lag non-linear model was used to examine the effects of DTR, after controlling for daily mean temperature, air pollutants, season and day of the week. A 1 °C increase in DTR at lag 0-4 days was associated with a 0.47% (95% confidence interval: 0.01%-0.93%) increase in non-accidental mortality. Stroke mortality was most sensitive to DTR. Female, the elderly and those with low education were more susceptible to DTR than male, the youth and those with high education, respectively. Our findings suggest that vulnerable subpopulations should pay more attention to protect themselves from unstable daily weather.

The burden of COPD mortality due to ambient air pollution in Guangzhou, China.

Few studies have investigated the chronic obstructive pulmonary disease (COPD) mortality fraction attributable to air pollution and modification by individual characteristics of air pollution effects. We applied distributed lag non-linear models to assess the associations between air pollution and COPD mortality in 2007–2011 in Guangzhou, China, and the total COPD mortality fraction attributable to air pollution was calculated as well. We found that an increase of 10 μg/m3 in particulate matter with an aerodynamic diameter of 10 μm or less (PM10), sulfur dioxide (SO2) and nitrogen dioxide (NO2) was associated with a 1.58% (95% confidence interval (CI): 0.12–3.06%), 3.45% (95% CI: 1.30–5.66%) and 2.35% (95% CI: 0.42–4.32%) increase of COPD mortality over a lag of 0–15 days, respectively. Greater air pollution effects were observed in the elderly, males and residents with low educational attainment. The results showed 10.91% (95% CI: 1.02–9.58%), 12.71% (95% CI: 5.03–19.85%) and 13.38% (95% CI: 2.67–22.84%) COPD mortality was attributable to current PM10, SO2 and NO2 exposure, respectively. In conclusion, the associations between air pollution and COPD mortality differed by individual characteristics. There were remarkable COPD mortality burdens attributable to air pollution in Guangzhou.

Excess Winter Mortality and Cold Temperatures in a Subtropical City, Guangzhou, China

Background A significant increase in mortality was observed during cold winters in many temperate regions. However, there is a lack of evidence from tropical and subtropical regions, and the influence of ambient temperatures on seasonal variation of mortality was not well documented. Methods This study included 213,737 registered deaths from January 2003 to December 2011 in Guangzhou, a subtropical city in Southern China. Excess winter mortality was calculated by the excess percentage of monthly mortality in winters over that of non-winter months. A generalized linear model with a quasi-Poisson distribution was applied to analyze the association between monthly mean temperature and mortality, after controlling for other meteorological measures and air pollution. Results The mortality rate in the winter was 26% higher than the average rate in other seasons. On average, there were 1,848 excess winter deaths annually, with around half (52%) from cardiovascular diseases and a quarter (24%) from respiratory diseases. Excess winter mortality was higher in the elderly, females and those with low education level than the young, males and those with high education level, respectively. A much larger winter increase was observed in out-of-hospital mortality compared to in-hospital mortality (45% vs. 17%). We found a significant negative correlation of annual excess winter mortality with average winter temperature (rs=-0.738, P=0.037), but not with air pollution levels. A 1 °C decrease in monthly mean temperature was associated with an increase of 1.38% (95%CI:0.34%-2.40%) and 0.88% (95%CI:0.11%-1.64%) in monthly mortality at lags of 0-1 month, respectively. Conclusion Similar to temperate regions, a subtropical city Guangzhou showed a clear seasonal pattern in mortality, with a sharper spike in winter. Our results highlight the role of cold temperature on the winter mortality even in warm climate. Precautionary measures should be strengthened to mitigate cold-related mortality for people living in warm climate.

The burden of ambient temperature on years of life lost in Guangzhou, China.

Limited evidence is available on the association between temperature and years of life lost (YLL). We applied distributed lag non-linear model to assess the nonlinear and delayed effects of temperature on YLL due to cause-/age-/education-specific mortality in Guangzhou, China. We found that hot effects appeared immediately, while cold effects were more delayed and lasted for 14 days. On average, 1 °C decrease from 25th to 1st percentile of temperature was associated with an increase of 31.15 (95%CI: 20.57, 41.74), 12.86 (8.05, 17.68) and 6.64 (3.68, 9.61) YLL along lag 0–14 days for non-accidental, cardiovascular and respiratory diseases, respectively. The corresponding estimate of cumulative hot effects (1 °C increase from 75th to 99th percentile of temperature) was 12.71 (−2.80, 28.23), 4.81 (−2.25, 11.88) and 2.81 (−1.54, 7.16). Effect estimates of cold and hot temperatures-related YLL were higher in people aged up to 75 years and persons with low education level than the elderly and those with high education level, respectively. The mortality risks associated with cold and hot temperatures were greater on the elderly and persons with low education level. This study highlights that YLL provides a complementary method for assessing the death burden of temperature.

Estimating years of life lost from cardiovascular mortality related to air pollution in Guangzhou, China

Previous studies have mainly used mortality or morbidity as the health outcome to examine the air pollution-health association. Little evidence is available on relationships between air pollutants and years of life lost (YLL). We aimed to estimate the YLL from cardiovascular mortality due to air pollution. Daily data on weather and air pollutants and individual data of all registered deaths for years 2004-2007 were obtained in Guangzhou, China. The generalized additive model was used to assess the YLL associated with 10μg/m3 increases in NO2, SO2 and PM10. We found that the mean daily YLL was 248, 87.5 and 73.7 for deaths from cardiovascular disease (CVD), stroke and ischemic heart disease (IHD), respectively. A significant linear correlation was observed between air pollution and YLL due to cardiovascular disease. The effects of air pollutants on YLL were immediate and lasted for two days. A 10μg/m3 increase above the corresponding threshold of 55.6μg/m3, 40.4μg/m3 and 0μg/m3 in NO2, PM10 and SO2 was related to YLL increase of 1.8 (95% CI: 0.8-2.9), 2.8 (1.7-3.8) and 2.6 (1.2-4.0) years at lag 0-1days for CVD, respectively. The estimates of YLL associated with NO2 and PM10 were higher in men than women. The air pollutants-related YLL was higher among young people and those with low education level, compared to the elderly and those with high education level, respectively. These findings confirmed YLL provides a complementary strategy for assessing the health effect of air pollution. This study underscores the necessity of the reduction of air pollution benefiting public health.

Comparison of the efficacy of rosuvastatin versus atorvastatin in preventing contrast induced nephropathy in patient with chronic kidney disease undergoing percutaneous coronary intervention.

Objectives We prospectively compared the preventive effects of rosuvastatin and atorvastatin on contrast-induced nephropathy (CIN) in patients with chronic kidney disease (CKD) undergoing percutaneous coronary intervention (PCI). Methods We enrolled 1078 consecutive patients with CKD undergoing elective PCI. Patients in Group 1 (n = 273) received rosuvastatin (10 mg), and those in group 2 (n = 805) received atorvastatin (20 mg). The primary end-point was the development of CIN, defined as an absolute increase in serum creatinine ≥0.5 mg/dL, or an increase ≥25% from baseline within 48–72 h after contrast medium exposure. Results CIN was observed in 58 (5.4%) patients. The incidence of CIN was similar in patients pretreated with either rosuvastatin or atorvastatin (5.9% vs. 5.2%, p = 0.684). The same results were also observed when using other definitions of CIN. Clinical and procedural characteristics did not show significant differences between the two groups (p>0.05). Additionally, there were no significant inter-group differences with respect to in-hospital mortality rates (0.4% vs. 1.5%, p = 0.141), or other in-hospital complications. Multivariate logistic regression analysis revealed that rosuvastatin and atorvastatin demonstrated similar efficacies for preventing CIN, after adjusting for potential confounding risk factors (odds ratio = 1.17, 95% confidence interval, 0.62–2.20, p = 0.623). A Kaplan–Meier survival analysis showed that patients taking either rosuvastatin or atorvastatin had similar incidences of all-cause mortality (9.4% vs. 7.1%, respectively; p = 0.290) and major adverse cardiovascular events (29.32% vs. 23.14%, respectively; p = 0.135) during follow-up. Conclusions Rosuvastatin and atorvastatin have similar efficacies for preventing CIN in patients with CKD undergoing PCI.

A comparison of four methods for the analysis of N-of-1 trials.

Objective To provide a practical guidance for the analysis of N-of-1 trials by comparing four commonly used models. Methods The four models, paired t-test, mixed effects model of difference, mixed effects model and meta-analysis of summary data were compared using a simulation study. The assumed 3-cycles and 4-cycles N-of-1 trials were set with sample sizes of 1, 3, 5, 10, 20 and 30 respectively under normally distributed assumption. The data were generated based on variance-covariance matrix under the assumption of (i) compound symmetry structure or first-order autoregressive structure, and (ii) no carryover effect or 20% carryover effect. Type I error, power, bias (mean error), and mean square error (MSE) of effect differences between two groups were used to evaluate the performance of the four models. Results The results from the 3-cycles and 4-cycles N-of-1 trials were comparable with respect to type I error, power, bias and MSE. Paired t-test yielded type I error near to the nominal level, higher power, comparable bias and small MSE, whether there was carryover effect or not. Compared with paired t-test, mixed effects model produced similar size of type I error, smaller bias, but lower power and bigger MSE. Mixed effects model of difference and meta-analysis of summary data yielded type I error far from the nominal level, low power, and large bias and MSE irrespective of the presence or absence of carryover effect. Conclusion We recommended paired t-test to be used for normally distributed data of N-of-1 trials because of its optimal statistical performance. In the presence of carryover effects, mixed effects model could be used as an alternative.

Excessively High Hydration Volume May Not Be Associated With Decreased Risk of Contrast‐Induced Acute Kidney Injury After Percutaneous Coronary Intervention in Patients With Renal Insufficiency

Background No well‐defined protocols currently exist regarding the optimal rate and duration of normal saline administration to prevent contrast‐induced acute kidney injury (CI‐AKI) in patients with renal insufficiency. Methods and Results Hydration volume ratios (hydration volume/weight; HV/W) were calculated in 1406 patients with renal insufficiency (estimated glomerular filtration rate [eGFR], <90 mL/min per 1.73 m2) undergoing percutaneous coronary intervention (PCI) with routine speed hydration (1 or 0.5 mL/kg per hour). We investigated the relationship between hydration volume, risk of CI‐AKI (increase in serum creatinine ≥0.5 mg/dL or 25% within 48–72 hours), and prognosis. Mean follow‐up duration was 2.85±0.88 years. Individuals with higher HV/W were more likely to develop CI‐AKI (quartiles: Q1, Q2, Q3, and Q4: 4.3%, 6.6%, 10.9%, and 15.0%, respectively; P<0.001). After adjusting 12 confounders, including age, sex, eGFR, anemia, emergent PCI, diabetes mellitus, chronic heart failure, diuretics, contrast volume, lesions, smoking status, and number of stents, multivariate analysis showed that a higher HV/W ratio was not associated with a decreased CI‐AKI risk (Q2 vs Q1: adjusted odds ratio [OR], 1.13; Q3 vs Q1: adjusted OR, 1.51; Q4 vs Q1: adjusted OR, 1.87; all P>0.05) and even increased CI‐AKI risk (HV/W >25 mL/kg: adjusted OR, 2.11; 95% CI, 1.24–3.59; P=0.006). Additionally, higher HV/W was significantly associated with an increased risk of death (Q4 vs Q1: adjusted hazard ratio, 3.44; 95% CI, 1.20–9.88; P=0.022). Conclusions Excessively high hydration volume at routine speed might be associated with increased risk of CI‐AKI and death post‐PCI in patients with renal insufficiency.

Safe Limits of Contrast Vary With Hydration Volume for Prevention of Contrast-Induced Nephropathy After Coronary Angiography Among Patients With a Relatively Low Risk of Contrast-Induced Nephropathy

Background—Few studies have investigated the safe limits of contrast to prevent contrast-induced nephropathy (CIN) based on hydration data. We aimed to investigate the relative safe maximum contrast volume adjusted for hydration volume in a population with a relatively low risk of CIN. Methods and Results—The ratios of contrast volume-to-creatinine clearance (V/CrCl) and hydration volume to body weight (HV/W) were determined in patients undergoing cardiac catheterization. Receiver–operator characteristic curve analysis based on the maximum Youden index was used to identify the optimal cutoff for V/CrCl in all patients and in HV/W subgroups. Eighty-six of 3273 (2.6%) patients with mean CrCl 71.89±27.02 mL/min developed CIN. Receiver–operator characteristic curve analysis indicated that a V/CrCl ratio of 2.44 was a fair discriminator for CIN in all patients (sensitivity, 73.3%; specificity, 70.4%). After adjustment for other confounders, V/CrCl >2.44 continued to be significantly associated with CIN (adjusted odds ratio, 4.12; P<0.001) and the risk of death (adjusted hazard ratio, 2.62; P<0.001). The mean HV/W was 12.18±7.40. We divided the patients into 2 groups (HV/W ⩽12 and >12 mL/kg). The best cutoff value for V/CrCl was 1.87 (sensitivity, 67.9%; specificity, 64.4%; adjusted odds ratio, 3.24; P=0.011) in the insufficient hydration subgroup (HV/W, ⩽12 mL/kg; CIN, 1.32%) and 2.93 (sensitivity, 69.0%; specificity, 65.0%; adjusted odds ratio, 3.04; P=0.004) in the sufficient hydration subgroup (HV/W, >12 mL/kg; CIN, 5.00%). Conclusions—The V/CrCl ratio adjusted for HV/W may be a more reliable predictor of CIN and even long-term outcomes after cardiac catheterization. We also found a higher best cutoff value for V/CrCl to predict CIN in patients with a relatively sufficient hydration status, which may be beneficial during decision-making about contrast dose limits in relatively low-risk patients with different hydration statuses.