Long-term exposure to ambient air pollution and asthma symptom score in the CONSTANCES cohort

Examining the impact of air pollution, climate change, and social determinants of health on asthma and environmental justice

PURPOSE OF REVIEW

In this review, we discuss the current literature examining the impact air pollution and climate change has on asthma onset, control, and exacerbation. This review also addresses the risk of exposure to specific disproportionately affected communities, highlighting health disparities in exposure and asthma outcomes.

RECENT FINDINGS

Recent studies have shifted from highlighting the associations between asthma exacerbations and indoor and outdoor air pollution. Studies are now focused on confirming the association of asthma incidence from these same exposures. Many studies have linked particulate matter to adverse asthma outcomes, however, the pollutant exposures that pose the greatest risk and the effect of natural disasters fueled by climate change are under current study. Some studies have observed that the true burden that pollutant exposures have on asthma outcomes occurs at the intersection of exposure and vulnerability. Future studies in this area will address social determinants of health, societal factors such as redlining and other systemic racism practices.

SUMMARY

Although decades of research support the causal link between gaseous and particulate air pollution and the exacerbation of preexisting asthma, recent studies suggest air pollution can cause incident (new onset) asthma. Studies have started to focus on the underlying drivers of poor outcomes in asthma. Many of the structural impediments to high quality asthma care at the society level (e.g. poverty, redlining, systemic racism) also are risk factors for worsened climate events and air pollution exposure. The individuals in these disproportionately affected groups are doubly affected by worsened exposure and worsened access to care for the resultant asthma exacerbations or incident asthma. More research is needed to understand the specific climate and air pollution mitigation efforts where disproportionately affected communities would derive the most benefit.

Adjuvant effect of inhaled particulate matter containing free radicals following house-dust mite induction of asthma in mice

INTRODUCTION

Exposures to particulate matter (PM) from combustion sources can exacerbate preexisting asthma. However, the cellular and molecular mechanisms by which PM promotes the exacerbation of asthma remain elusive. We used a house dust mite (HDM)-induced mouse model of asthma to test the hypothesis that inhaled DCB230, which are PM containing environmentally persistent free radicals (EPFRs), will aggravate asthmatic responses.

METHODS

Groups of 8-10-week-old C57BL/6 male mice were exposed to either air or DCB230 aerosols at a concentration of 1.5 mg/m3 4 h/day for 10 days with or without prior HDM-induction of asthma.

RESULTS

Aerosolized DCB230 particles formed small aggregates (30-150 nm). Mice exposed to DCB230 alone showed significantly reduced lung tidal volume, overexpression of the Muc5ac gene, and dysregulation of 4 inflammation related genes, Ccl11, Ccl24, Il-10, and Tpsb2. This suggests DCB230 particles interacted with the lung epithelium inducing mucous hypersecretion and restricting lung volume. In addition to reduced lung tidal volume, compared to respective controls, the HDM + DCB230-exposed group exhibited significantly increased lung tissue damping and up-regulated expression of Muc5ac, indicating that in this model, mucous hypersecretion may be central to pulmonary dysfunction. This group also showed augmented lung eosinophilic inflammation accompanied by an up-regulation of 36 asthma related genes. Twelve of these genes are part of IL-17 signaling, suggesting that this pathway is critical for DCB230 induced toxicity and adjuvant effects in lungs previously exposed to HDM.

CONCLUSION

Our data indicate that inhaled DCB230 can act as an adjuvant, exacerbating asthma through IL-17-mediated responses in a HDM mouse model.

Long-Term PM2.5 Exposure, Lung Function, and Cognitive Function Among Middle-Aged and Older Adults in China

BACKGROUND

Long-term exposure to PM2.5 is related to poor lung function and cognitive impairment, but less is known about the pathway involved in this association. We aimed to explore whether the effect of PM2.5 on cognitive function was mediated by lung function.

METHODS

A total of 7 915 adults older than 45 years old were derived from the China Health and Retirement Longitudinal Study (CHARLS) collected in 2011 and 2015. PM2.5 exposure was estimated using a geographically weighted regression model. Lung function was measured by peak expiratory flow (PEF). Cognitive function was evaluated through a structured questionnaire with 4 dimensions: episodic memory, attention, orientation, and visuoconstruction. Under the counterfactual framework, causal mediation analysis was applied to examine direct and indirect associations.

RESULTS

An interquartile range (IQR) increase in PM2.5 change was significantly related to an 8.480 (95% confidence interval [CI]: 3.116, 13.845) decrease in PEF change and a 0.301 (95% CI: 0.100, 0.575) decrease in global cognitive score change. The direct and indirect effects of PM2.5 exposure on global cognitive performance were -0.279 (95% CI: -0.551, -0.060) and -0.023 (95% CI: -0.041, -0.010), respectively. The proportion of the indirect effect was 7.48% (p = .010). The same significant association appeared in only 2 dimensions, episodic memory and attention, which were both mediated by PEF.

CONCLUSIONS

Lung function played a partially mediating role in the association between long-term PM2.5 exposure and cognition. More clean air actions should be undertaken to improve lung function and cognitive function in older adults.

Bi-directional associations between depressive symptoms and asthma in middle-aged and elderly adults in China

BACKGROUND

There is currently no evidence of an association between depressive symptoms and asthma among older adults in China. We explored the bi-directional associations between depressive symptoms and asthma, and their changes in middle-aged and elderly adults from a national cohort.

METHODS

A longitudinal cohort study was conducted with a total of 17,708 individuals from 150 urban communities and 450 rural villages in 28 provinces in China.

RESULTS

After making exclusions, 11,492 and 8604 participants were included for incident asthma and incident depressive symptoms analysis, respectively. The incidence density was 4.46 and 10.24 for every 1000 person-years, respectively. Baseline depressive symptoms were associated with a higher risk of incident asthma (Hazard ratio [HR] = 1.60, 95 % confidence interval [CI]: 1.27, 2.02). Decreased depressive symptoms during baseline or follow-ups or both baseline and follow-ups were associated with a lower risk of incident asthma (P_{for trend} < 0.0001). Every 1-score increment of CES-D score was associated with a 4 % increase in asthma, with a non-linear association (P = 0.04) between CES-D score (break point = 7) and asthma. Asthma status increased the risk of participants with severe depressive symptoms (HR = 1.51, 95 % CI: 1.19, 1.92), especially in males (P_{for interaction} = 0.02).

LIMITATIONS

Depressive symptoms and asthma were assessed by validated questionnaires instead of clinical diagnosis.

CONCLUSIONS

Bi-directional associations between asthma and depressive symptoms do exist. Effective measures should be taken to reduce depressive symptoms and the risk of incident asthma in middle aged and elderly adults in China.