Air Pollution Tightly Tied to CV Disease, Chinese Study Confirms

More evidence, this time out of China, is strengthening the case that air pollution plays a causative role in cardiovascular disease.

Chinese college students participating in the randomized, double-blind crossover trial who encountered greater amounts of fine particulate matter (PM) were more likely to have high blood pressure, biomarkers of oxidative stress, inflammation, insulin resistance, and hormones.

“Ambient PM exposure has been suggested to be associated with increased risks of respiratory, cardiovascular and metabolic diseases, but the mechanisms [are] still not well-established,” senior author Haidong Kan, MD, PhD (Fudan University, Shanghai, China), explained to TCTMD via email. The new research findings further explain how exposure to air pollution translates into higher cardiovascular risk, Kan said.

“Our results may indicate that particulate matter could affect the human body in more ways than we currently know. Thus, it is increasingly necessary for people to understand the importance of reducing their PM exposure,” he elaborated.

The paper, published online August 14, 2017, in Circulation, provides an assessment of how serum metabolites vary based on reductions of PM exposure.

Link Seen in Healthy College Students

From November to December 2015, Kan et al studied 60 college students living in 17 different dormitories at Fudan University in Shanghai. The students were expected not to cook or clean during the study, in order to limit their exposure to PM. At baseline, participants did not have allergies or any respiratory or cardiovascular conditions.

Kan along with lead authors Huichu Li, MS, and Jing Cai, PhD, and colleagues put air purifiers—half sham and half real—in the students’ dorms for two 9-day cycles with a 12-day washout period in between. Liquid chromatography-mass spectrometry and gas chromatography mass spectrometry were used to measure the serum metabolites.

Higher exposure to fine particulate matter (≤ 2.5 µm in diameter) was associated with significantly higher levels of cortisol, cortisone, epinephrine, and norepinephrine and differences in glucose, amino acid, fatty acid, and lipid levels.

Healthcare providers should be on the vanguard of advocacy groups in support of robust national air quality regulations to help lessen the threat of PM2.5 to their patients. Robert D. Brook

These differences appeared to carry negative health effects, Li et al observe. “We found significantly higher blood pressure, hormones, insulin resistance, and biomarkers of oxidative stress and inflammation among individuals exposed to higher PMs with aerodynamic diameters ≤ 2.5 μm.”

Overall, the results “suggest that higher PM may induce metabolic alteration that are consistent with activations of the hypothalamus-pituitary-adrenal and sympathetic-adrenal-medullary axes, adding potential mechanistic insights into the adverse health outcomes associated with PM,” the researchers conclude.

‘Vast Array of Metabolic Abnormalities’

Robert D. Brook, MD (University of Michigan, Ann Arbor), who wrote an editorial accompanying the paper, told TCTMD in an email, “One of the most fascinating findings was the large extent of the vast array of metabolic abnormalities (previously unknown) induced by PM2.5.”

According to Brook, the “take-home message” is that exposure PM2.5 seems to be a key risk factor for cardiovascular conditions such as MI, congestive heart failure, and stroke as well as metabolic disorders such as diabetes and hypertension.

“Cardiologists should be aware of this important global public health issue,” he stressed, adding, “Healthcare providers should be on the vanguard of advocacy groups in support of robust national air quality regulations to help lessen the threat of PM2.5 to their patients. They should also be better informed, in order to be able to provide expert and sound advice to their patients regarding the health risks of air pollution, for example, to high-risk patients with heart disease traveling to highly polluted regions.”

Future efforts, Kan noted, “should examine whether these health benefits from short-term air purification could be maintained and translated into improved health in the long term, and whether these findings could also be found in residents from low-PM areas.” He suggested studies might also look further into how breathing PM could affect the nervous system and hormone secretion.

As to what can be done now, the paper suggests that “indoor air purification is a practical way to reduce personal exposure to PMs and may improve cardiovascular health in the long run.”