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Higher levels of traffic pollution tied to lower levels of HDL cholesterol (2017-04-26)

Scientists examined relationship between air pollution and both HDL cholesterol and HDL particle number in the MESA Air study (Multi-Ethnic Study of Atherosclerosis Air Pollution).

High-density lipoprotein (HDL) cholesterol helps curb the odds of heart disease by purging blood vessels of debris and lowering levels of triglycerides, dangerous fats that can make blood thicker, stickier and more prone to clots.

Researchers studied 6,654 adults and found people exposed to higher levels of fine, ultrafine particles (PM2.5) and black carbon concentrations in traffic pollution tended to have lower levels of HDL cholesterol in their blood.

Exposure periods were averaged to 12 months, 3 months, and 2 weeks prior to examination.

HDL cholesterol and HDL particle number were measured in the year 2000 using the cholesterol oxidase method and nuclear magnetic resonance spectroscopy, respectively.

Researchers used multivariable linear regression to examine the relationship between air pollution exposure and HDL measures.

Study participants were 62 years old on average, and half of them were current or former smokers.
About 16 percent of the participants took cholesterol-lowering drugs and roughly 45 percent had high blood pressure.
None had cardiovascular disease at the start of the study period.

Researchers used participants’ home addresses to estimate average exposure to PM 2.5 and black carbon over 12-month, three-month and two-week periods in the year 2000.

They also looked at blood levels of HDL cholesterol and another measure known as HDL particle count, which some scientists believe may be a more accurate way to assess heart disease risk.

Over one year, people exposed to more black carbon had lower levels of HDL cholesterol than participants with little or no exposure to black carbon. The difference was small, but statistically meaningful.

Higher black carbon exposure over one year was also associated with lower HDL particle counts, but this difference was too small to rule out the possibility that it was due to chance, researchers report in the journal Arteriosclerosis, Thrombosis, and Vascular Biology.

Over three months, however, the picture looked different.

In this shorter-term analysis, higher levels of fine particulate matter were associated with a lower HDL particle count.

The slightly lower level of HDL cholesterol seen with high pollution exposure was too small a difference to rule out chance, but it was still comparable to the rise in HDL seen when smokers quit, the researchers note.

The study wasn’t a controlled experiment designed to prove how traffic fumes directly influence cholesterol or the risk of heart disease.

These data are consistent with the hypothesis that exposure to air pollution is adversely associated with measures of HDL.

For more information
Arteriosclerosis, Thrombosis, and Vascular Biology
Association of Air Pollution Exposures With High-Density Lipoprotein Cholesterol and Particle Number