A case-crossover analysis of the relationship of air pollution with out-of-hospital sudden unexpected death in Wake County, North Carolina (2013-2015)

Fine particulate matter-sudden death association modified by ventricular hypertrophy and inflammation: a case-crossover study

Background

Sudden death accounts for approximately 10% of deaths among working-age adults and is associated with poor air quality. Objectives: To identify high-risk groups and potential modifiers and mediators of risk, we explored previously established associations between fine particulate matter (PM2.5) and sudden death stratified by potential risk factors.

Methods

Sudden death victims in Wake County, NC, from 1 March 2013 to 28 February 2015 were identified by screening Emergency Medical Systems reports and adjudicated (n = 399). Daily PM2.5 concentrations for Wake County from the Air Quality Data Mart were linked to event and control periods. Potential modifiers included greenspace metrics, clinical conditions, left ventricular hypertrophy (LVH), and neutrophil-to-lymphocyte ratio (NLR). Using a case-crossover design, conditional logistic regression estimated the OR (95%CI) for sudden death for a 5 μg/m3 increase in PM2.5 with a 1-day lag, adjusted for temperature and humidity, across risk factor strata.

Results

Individuals having LVH or an NLR above 2.5 had PM2.5 associations of greater magnitude than those without [with LVH OR: 1.90 (1.04, 3.50); NLR > 2.5: 1.25 (0.89, 1.76)]. PM2.5 was generally less impactful for individuals living in areas with higher levels of greenspace.

Conclusion

LVH and inflammation may be the final step in the causal pathway whereby poor air quality and traditional risk factors trigger arrhythmia or myocardial ischemia and sudden death. The combination of statistical evidence with clinical knowledge can inform medical providers of underlying risks for their patients generally, while our findings here may help guide interventions to mitigate the incidence of sudden death.

Short term exposure to air pollution and mortality in the US: a double negative control analysis

RATIONALE

Studies examining the association of short-term air pollution exposure and daily deaths have typically been limited to cities and used citywide average exposures, with few using causal models.

OBJECTIVES

To estimate the associations between short-term exposures to fine particulate matter (PM_2.5), ozone (O₃), and nitrogen dioxide (NO₂) and all-cause and cause-specific mortality in multiple US states using census tract or address exposure and including rural areas, using a double negative control analysis.

METHODS

We conducted a time-stratified case-crossover study examining the entire population of seven US states from 2000-2015, with over 3 million non-accidental deaths. Daily predictions of PM_2.5, O₃, and NO₂ at 1x1 km grid cells were linked to mortality based on census track or residential address. For each pollutant, we used conditional logistic regression to quantify the association between exposure and the relative risk of mortality conditioning on meteorological variables, other pollutants, and using double negative controls.

RESULTS

A 10 μg/m³ increase in PM_2.5 exposure at the moving average of lag 0-2 day was significantly associated with a 0.67% (95%CI: 0.34-1.01%) increase in all-cause mortality. 10 ppb increases in NO₂ or O₃ exposure at lag 0-2 day were marginally associated with and 0.19% (95%CI: -0.01-0.38%) and 0.20 (95% CI-0.01, 0.40), respectively. The adverse effects of PM_2.5 persisted when pollution levels were restricted to below the current global air pollution standards. Negative control models indicated little likelihood of omitted confounders for PM_2.5, and mixed results for the gases. PM_2.5 was also significantly associated with respiratory mortality and cardiovascular mortality.

CONCLUSIONS

Short-term exposure to PM_2.5 and possibly O₃ and NO₂ are associated with increased risks for all-cause mortality. Our findings delivered evidence that risks of death persisted at levels below currently permissible.

Associations between differences in anemia-related blood cell parameters and short-term exposure to ambient particle pollutants in middle-aged and elderly residents in Beijing, China

Anemia is a highly prevalent disease among older populations, with multiple adverse health outcomes, and particles exposure is a potential risk factor for anemia. However, evidence on associations of exposure to particles with small size with anemia-related blood cell parameters levels in the elderly is limited, and the underlying mechanisms are unclear. Based on a panel study in Beijing, we found that in 135 elderly participants, mass concentrations of particle with an aerodynamic diameter ≤ 2.5 μm (PM_2.5), black/elemental carbon (BC/EC, particle size range: 0-2.5 μm), and number concentrations of ultrafine particles (UFPs, particle size range: 5.6-93.1 nm) and accumulated mode particles (Acc, size range: 93.1-560 nm) were significantly associated with levels of red blood cell count (RBC), hemoglobin (HGB), hematocrit (HCT), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC). The mean ± SD for PM_2.5, UFPs, Acc, BC, OC, and EC were 69.7 ± 61.1 μg/m³, 12.5 ± 4.3 × 10³/cm³, 1.6 ± 1.2 × 10³/cm³, 3.0 ± 2.0 μg/m³, 8.7 ± 6.7 μg/m³, and 2.1 ± 1.6 μg/m³, respectively. Cotinine (higher than 50 ng/mL) is used as an indicator of smoking exposure. The association between MCHC difference and per interquartile range (IQR) increase in average UFPs concentration 14 d before clinical visits was -0.7% (95% CI: -1.1% to -0.3%). Significant associations of UFPs and Acc exposure with MCHC and MCH levels remain robust after adjustment for other pollutants. Furthermore, 25.2% (95% CI: 7.4% to 64.8%) and 29.8% (95% CI: 5.3% to 214.4%) of the difference in MCHC associated with average UFPs and Acc concentrations 14 d before clinical visits were mediated by the level of tumor necrosis factor α (TNF α), a biomarker of systemic inflammation. Our findings for the first time provide the evidence that short-term UFPs and Acc exposure contributed to the damage of anemia-related blood cell in the elderly, and systemic inflammation was a potential internal mediator.