The short-term effect of air pollution on cardiovascular mortality in Tianjin, China: comparison of time series and case-crossover analyses

Background

Many studies have illustrated that ambient air pollution negatively impacts on health. However, little evidence is available for the effects of air pollution on cardiovascular mortality (CVM) in Tianjin, China. Also, no study has examined which strata length for the time-stratified case-crossover analysis gives estimates that most closely match the estimates from time series analysis.

Objectives

The purpose of this study was to estimate the effects of air pollutants on CVM in Tianjin, China, and compare time-stratified case-crossover and time series analyses.

Method

A time-stratified case-crossover and generalized additive model (time series) were applied to examine the impact of air pollution on CVM from 2005 to 2007. Four time-stratified case-crossover analyses were used by varying the stratum length (Calendar month, 28, 21 or 14 days). Jackknifing was used to compare the methods. Residual analysis was used to check whether the models fitted well.

Results

Both case-crossover and time series analyses show that air pollutants (PM₁₀, SO₂ and NO₂) were positively associated with CVM. The estimates from the time-stratified case-crossover varied greatly with changing strata length. The estimates from the time series analyses varied slightly with changing degrees of freedom per year for time. The residuals from the time series analyses had less autocorrelation than those from the case-crossover analyses indicating a better fit.

Conclusion

Air pollution was associated with an increased risk of CVM in Tianjin, China. Time series analyses performed better than the time-stratified case-crossover analyses in terms of residual checking.     

封闭缺氧法杀灭和去除管道中的淡水壳菜研究

在人为隔绝氧气和食物等养分的条件下，研究了淡水壳菜的壳长、水温、其与原水体积比、水中溶解氧等因素对淡水壳菜生存状况的影响。结果表明，壳长为0～5mm的淡水壳菜对缺氧环境的耐受力较差，至第8天时就已完全死亡，而壳长为10～20mm的淡水壳菜则耐受力相对较强，达100％死亡率约需11d；高水温时水中溶解氧值下降明显，导致淡水壳菜的死亡速度加快，25℃时只需7d即全部死亡，而20℃时则需11d；淡水壳菜与原水的体积比越大则溶解氧的消耗越快，淡水壳菜的死亡率随之增加。当淡水壳菜与原水体积比分别为1／3（A组）和1／4（B组）时，自试验的第2天起A组的溶解氧值一直低于B组，至第7天时A、B两组的溶解氧分别降至1．49mg/L和2．01mg／L，并且A组在第7天达100％死亡率，B组则在第9天才全部死亡。     

Combined exposure to cyanobacterial biomass, lead and the Newcastle virus enhances avian toxicity

Under environmental conditions, wild birds can be exposed to multiple stressors including natural toxins, anthropogenic pollutants and infectious agents at the same time.This experimental study was successful in testing the hypothesis that adverse effects of cyanotoxins, heavy metals and a non-pathogenic immunological challenge combine to enhance avian toxicity. Mortality occurred in combined exposures to naturally occurring cyanobacterial biomass and lead shots, lead shots and Newcastle vaccination as well as in single lead shot exposure. Mostly acute effects around day 10 were observed. On day 30 of exposure, there were no differences in the liver accumulation of lead in single and combined exposure groups. Interestingly, liver microcystin levels were elevated in birds co-exposed to cyanobacterial biomass together with lead or lead and the Newcastle virus. Significant differences in body weights between all Pb-exposed and Pb-non-exposed birds were found on days 10 and 20. Single exposure to cyanobacterial biomass resulted in hepatic vacuolar dystrophy, whereas co-exposure with lead led to more severe granular dystrophy. Haematological changes were associated with lead exposure, in particular. Biochemical analysis revealed a decrease in glucose and an increase in lactate dehydrogenase in single and combined cyanobacterial and lead exposures, which also showed a decreased antibody response to vaccination.The combined exposure of experimental birds to sub-lethal doses of individual stressors is ecologically realistic. It brings together new pieces of knowledge on avian health. In light of this study, investigators of wild bird die-offs should be circumspect when evaluating findings of low concentrations of contaminants that would not result in mortality on a separate basis. As such it has implications for wildlife biologists, veterinarians and conservationists of avian biodiversity.     

Linking Centers for Medicare & Medicaid Services data with prospective DCOR trial data: Methods and data comparison results

The Dialysis Clinical Outcomes Revisited (DCOR) trial was a large randomized, multicenter 3‐year trial comparing the effects of sevelamer with calcium‐based binders on mortality, hospitalization, morbidity, and medical costs in hemodialysis subjects. Dialysis Clinical Outcomes Revisited was prospectively designed to link subjects to the Centers for Medicare & Medicaid Services End‐Stage Renal Disease (CMS ESRD) database to collect additional baseline characteristic data and to enhance outcome evaluation. Subjects were linked to the CMS ESRD database by means of an algorithm using several patient identifiers. Some baseline characteristic data were collected exclusively from the CMS ESRD database. Mortality and hospitalization end points were obtained from the CMS ESRD database and compared with similar data collected prospectively into a case‐report form (CRF) database. Of the 2103 patients who participated in the DCOR study, 2101 were successfully linked to the CMS ESRD database. Patient baseline data showed that treatment groups were well‐balanced, except that a higher proportion of subjects in the calcium‐based binder group had atherosclerotic heart disease. Calculated mortality rates were similar between databases, but more deaths were identified in the CMS than in the CRF database. These additional deaths were verified through several sources. More hospitalizations were also detected in the CMS than in the CRF database. The CMS database was a good source of death end points and hospitalization occurrence. Linking patients to the data‐rich CMS ESRD database allowed assessment of additional important secondary end points at a relatively low cost compared with prospective data collection.     

Lipid Metabolism and Cardiovascular Morbidity and Mortality in Hemodialysis Patients: Role of Factors Modulating Cytosolic Calcium

Animal studies indicate that insulin resistance and glucose intolerance leading to dyslipidemia in uremic rats are associated with increased cytosolic calcium ([Ca⁺⁺ i]). The resistance and intolerance are reversed with verapamil, but recur after its discontinuation. This finding suggests that hyperparathyroid‐induced [Ca ⁺⁺ i] increase is responsible for the metabolic derangement. We retrospectively examined, over a 12‐year period, the effects of factors that lower [Ca ⁺⁺i] on total serum cholesterol and triglycerides in 332 hemodialysis (HD) patients. Because the study was retrospective, detailed lipid profiles were not available. We therefore relied on morbidity and mortality outcomes related to atherosclerotic vascular disease. Patients with diabetes mellitus were excluded, because their dyslipidemia and vascular disease are mediated via a different mechanism. Four groups emerged: group I [high parathormone (PTH) in the absence of calcium channel blockers (CCBs), n = 107], representing the highest [Ca⁺⁺ i]; group II (high PTH in the presence of CCBs, n = 76) and group III (lower PTH in the absence of CCBs, n = 66), representing intermediate [Ca ⁺⁺ i]; and group IV (lower PTH in the presence of CCBs, n = 83) representing the lowest [Ca ⁺⁺i]. The theoretically lower [Ca ⁺⁺ i] was achieved via CCB therapy or lower PTH, or both. The mean serum cholesterol in group I was 322 ± 24 mg/dL and the level of triglycerides was 398 ± 34 mg/dL. Group II had mean serum cholesterol of 196 ± 16 mg/dL and triglycerides of 157 ± 17 mg/dL. Group III had a mean serum cholesterol of 202 ± 19 mg/dL and triglycerides of 160 ± 15 mg/dL. Group IV had a mean serum cholesterol of 183 ± 9 mg/dL and triglycerides of 94 ± 6 mg/dL. The differences in cholesterol and triglyceride levels among four groups were significant (p < 0.001) by one‐way analysis of variance (ANOVA). The incidence of cardiovascular morbidity and mortality events was 61% in group I, 24% in group II, 28% in group III, and 18% in group IV (χ ² = 47.7, p < 0.001). We conclude that, in non diabetic HD patients, hyperparathyroidism, especially in the absence of CCBs, is associated with severe dyslipidemia and increased risk of cardiovascular morbidity and mortality. Dyslipidemia may be related to a hyperparathyroid‐induced increase in cytosolic calcium [Ca⁺⁺i]. Lowering [Ca⁺⁺i] by decreasing PTH or by blocking calcium entry into cells (via CCBs), or both, is associated with less dyslipidemia and improved long‐term cardiovascular morbidity and mortality. Prospective randomized studies, with actual measurement of [Ca ⁺⁺i], are needed to verify the results of this study.     

Hypomagnesemia as a predictor of mortality in hemodialysis patients and the role of proton pump inhibitors: A cross‐sectional, 1‐year,retrospective cohort study

Introduction This study aimed to evaluate the association between proton pump inhibitor (PPI) use and serum magnesium levels, and the role of hypomagnesemia and PPI use as a risk factor for mortality in hemodialysis patients. Methods An observational study, including a cross‐sectional and 1‐year retrospective cohort study. The study comprised 399 hemodialysis patients at a single center, and was conducted from January to September 2014. Multiple linear regression analysis was used to investigate the independent relationship between serum magnesium levels and baseline demographic and clinical variables, including PPI and histamine‐2 receptor antagonist use. Cox regression model was used to identify lower serum magnesium level and PPI as a predictor of 1‐year mortality. Findings Serum magnesium levels were lower with PPI use than non‐PPI use (2.39 ± 0.36 vs. 2.56 ± 0.39 mg/dL, P < 0.001). Multiple linear regression analysis showed that PPI use, low serum albumin levels, and low serum potassium and high‐sensitivity C‐reactive protein (hs‐CRP) levels were significantly associated with low serum magnesium levels. A total of 29 deaths occurred during the follow‐up period. According to Cox regression analysis stratified by hs‐CRP, only high serum hs‐CRP levels (>4.04 mg/L) in association with low serum magnesium levels was an independent risk factor for 1‐year mortality (hazard ratio: 2.92; 95% CI: 1.53–6.40, P < 0.001). Discussion Serum magnesium levels are lower in PPI use. In the inflammatory state, a low serum magnesium level is a significant predictor of mortality in hemodialysis patients.     

Estimating the effect of dialysis staffing ratio regulations on mortality and hospitalizations for Medicare hemodialysis patients

Background and Objectives

Eight states and Washington, DC have implemented regulations mandating a minimum ratio between treatment staff and patients receiving hemodialysis in a facility in an effort to improve the quality of hemodialysis treatment. Our investigation examines the association between minimum staffing regulations and patient mortality for four states and hospitalizations for two states that implemented these rules during our sample period.

Design, Setting, Participants, and Measurements

We utilized a synthetic difference in differences estimation to analyze the effect of minimum staffing ratios on hemodialysis treatment quality, measured by deaths and hospitalizations for end-stage renal disease patients. We used data gathered by the US Renal Data System and aggregated at the state level.

Results

We are unable to find evidence that mandated dialysis staffing ratios area associated with a reduction in mortality or hospitalizations. We estimate a slight reduction in deaths per 1000 patient hours and a slight increase in hospitalizations, but neither are statistically significant.

Conclusions

We were unable to find evidence that minimum staffing ratios for hemodialysis facilities are associated with improved patient outcomes. Our findings highlight the need for future work, studying the impact of these regulations at the facility level.     

Survival pattern of hemodialysis patients in Kumasi, Ghana: A summary of forty patients initiated on hemodialysis at a new hemodialysis unit

To evaluate the survival pattern of hemodialysis patients at a dialysis unit in Kumasi, Ghana, through a retrospective (observational) study. Patients who were placed on hemodialysis at the dialysis unit at Komfo Anokye teaching hospital from October 25, 2006 to December 2007. The patients were followed from initiation of dialysis until December 31, 2007. The overall mortality was 14 (35.9%) on the incident population for the period and that for the first 90 days was 12 (32.4%) patients. Chronic glomerulonephritis was the underlying kidney disease in 35.9%. This was followed by hypertension (19.1%) and diabetes mellitus (15.4%), respectively. Cardiovascular diseases accounted for 42% of mortality. This was followed by septicemia (25%) from the access site and anemia (25%). Fifty percent of the patients were able to afford 20 sessions of hemodialysis before stopping. The most powerful predictors of survival were the duration of hemodialysis (P=0.05) and the number of hemodialysis sessions (P=0.02). Age at initiation of hemodialysis was not significant. First 90-day mortality of patients on hemodialysis is high in poor African countries. This is due partially to the late referral of patients and also the cost of the dialysis treatment. Efforts will have to be made to reduce the cost of the dialysis treatment. Reuse technology (of dialyzer, etc.) should be introduced to cut down the cost of hemodialysis. Peritoneal dialysis should also be introduced for highly motivated patients. Efforts should also be made to reduce the increasing incidence of kidney disease, and finally third-world countries should consider establishing kidney transplantation, that is cost effective.     

FGF-23 is associated with cardiac troponin T and mortality in hemodialysis patients

Fibroblast growth factor 23 (FGF-23) is elevated in patients with end-stage kidney disease and has been linked with mortality, vascular calcification, markers of bone turnover, and left ventricular hypertrophy. In this cohort study, we determined the correlates of FGF-23 (including cardiac troponin T [cTNT]) and determined its association with mortality over 3.5 years of follow-up in 103 prevalent hemodialysis patients. Mean age was 61.2 (15.5) and the mean dialysis vintage was 4.19 years (4.6). The median (interquartile range) FGF-23 was 1259 (491, 2885) RU/mL. Independent predictors (estimate standard error) of log-transformed FGF-23 concentrations included phosphorus (0.75 [0.237], P = 0.002) and cardiac troponin T (1.04 [0.41], P = 0.01). There were 57 deaths. In the fully adjusted model, the significant predictors of mortality included age and albumin. The independent association between FGF-23 and cTNT is a novel finding. Whether this relationship supports the possibility that a downstream effect of dysregulated phosphorous homeostasis may be enhanced cardiac remodeling requires further study.     

Determinants of survival in patients receiving dialysis in Libya

Maintenance dialysis is associated with reduced survival when compared with the general population. In Libya, information about outcomes on dialysis is scarce. This study, therefore, aimed to provide the first comprehensive analysis of survival in Libyan dialysis patients. This prospective multicenter study included all patients in Libya who had been receiving dialysis for >90 days in June 2009. Sociodemographic and clinical data were collected upon enrolment and survival status after 1 year was determined. Two thousand two hundred seventy‐three patients in 38 dialysis centers were followed up for 1 year. The majority were receiving hemodialysis (98.8%). Sixty‐seven patients were censored due to renal transplantation, and 46 patients were lost to follow‐up. Thus, 2159 patients were followed up for 1 year. Four hundred fifty‐eight deaths occurred, (crude annual mortality rate of 21.2%). Of these, 31% were due to ischemic heart disease, 16% cerebrovascular accidents, and 16% due to infection. Annual mortality rate was 0% to 70% in different dialysis centers. Best survival was in age group 25 to 34 years. Binary logistic regression analysis identified age at onset of dialysis, physical dependency, diabetes, and predialysis urea as independent determinants of increased mortality. Patients receiving dialysis in Libya have a crude 1‐year mortality rate similar to most developed countries, but the mean age of the dialysis population is much lower, and this outcome is thus relatively poor. As in most countries, cardiovascular disease and infection were the most common causes of death. Variation in mortality rates between different centers suggests that survival could be improved by promoting standardization of best practice.