People living in areas with high air pollution have less ‘good cholesterol’ which is vital for heart health, suggests a new study.
Numerous studies in the past have found a link between exposure to air pollution and a higher risk of cardiovascular disease. However, this new study points to a certain type of cholesterol that may be affected by air pollution.
“Our study helps strengthen the biological plausibility of the link between traffic-related air pollution and cardiovascular disease,” says lead author Dr Griffith Bell, from the University of Washington School of Public Health in Seattle, in the U.S.
“We’re slowly beginning to understand some of the biology of how that link works.”
The British Heart Foundation described air pollution as a “silent killer” responsible for a “myriad of changes in the body”, such as high blood pressure.
Air pollution kills around 40,000 people in the UK each year. Of these deaths, 8 in 10 are caused by stroke or a heart attack, according to Professor Sir Nilesh Samani, medical director of the British Heart Foundation.
“Good cholesterol,” or high density lipoprotein (HDL) is beneficial for the heart because it removes low-density lipoprotein (LDL) cholesterol, or “bad” cholesterol, from the arteries.
Accumulation of LDL can cause atherosclerosis, a hardening or narrowing of the arteries that increases the risk of heart attack and stroke.
For their study, Dr. Bell and colleagues analysed the data of 6,654 people in the U.S. aged 45 to 84 taking part in the Multi-Ethnic Study of Atherosclerosis.
The researchers estimated air pollution of each individual by using information from cohort-focused monitoring campaigns, which revealed the city in which each of the participants lived, when they lived there, and the air pollution levels in each city at that time.
Overall levels of HDL cholesterol in each individual, as well as the number of HDL particles were also assessed. According to recent studies, the HDL particle number may more accurately indicate how HDL helps the heart, compared with the cholesterol content of HDL particles.
The researchers found that people with higher exposure to particulate matter, known as PM 2.5, which are produced by burning fossil fuels, were linked to less HDL.
Over a 1-year period, participants with higher exposure to black carbon – a component of PM that is primarily emitted from automobiles – had significantly lower levels of HDL cholesterol, than those who had lower black carbon exposure.
Although reductions in HDL cholesterol as a result of higher exposure to air pollution was seen in both sexes, the effect was stronger for women, the authors note.
Dr Bell says, the lower HDL levels linked with greater air pollution exposure may increase the later risk of cardiovascular disease.
The researchers say their study has provided some insight into how air pollution affects heart health, but more research is needed to gain a clearer understanding.
The study was published in the journal Arteriosclerosis, Thrombosis, and Vascular Biology,