Beyond BMI
Waist size can show who is most at risk from air pollution
Ultrafine particulate air pollution floats through the air like a miasma, leaving heart disease, dementia, and asthma in its wake. But ultrafine pollution doesn’t affect everyone equally. Researchers from the University of Connecticut and Tufts University report on July 28 in the American Journal of Preventive Cardiology that a larger waist—indicating more fat around the organs—makes people more vulnerable.
Particulate air pollution can be big enough to be visible to the naked eye, like dust or wildfire soot, or as small as particles of car exhaust just 1/1000 the width of a human hair. The tiniest particles are capable of the most harm, slipping into the bloodstream and traveling throughout the body. This ultrafine particulate matter, defined as particles less than 100 nanometers in diameter, is known to increase the risk of cardiovascular disease, dementia, high blood pressure, and respiratory illnesses.
UConn School of Medicine environmental researcher Doug Brugge has spent years working with a community living within 200 meters of Interstate-93 in Massachusetts, just north of Boston. Their exposure to ultrafine particulate matter is much higher than average in the US. Recently, Brugge and his colleagues began looking at whether members of the community would benefit from using High Efficiency Particulate Air (HEPA) filters in their homes to protect them from particulate pollution. The study included 116 people who used either a HEPA or a sham filter for 30 days, and then switched. To judge whether the HEPA filters had helped, the researchers measured blood levels of tiny proteins known to promote inflammation and cardiovascular disease. Although the initial results of the study showed that on average, the HEPA filter made no difference, HEPA filtration made a very significant difference for a certain group of people.
Brugge was discussing the results of the study with a biostatistician from Tufts University, Misha Eliasziw. Eliasziw pointed out from her analysis of the data that people who benefited from the HEPA filter shared one specific characteristic: they had excessive visceral fat, meaning fat around the abdominal organs, as indicated by the circumference of their waist compared to their height and weight.
Eliasziw considered this to be a more significant measure of harmful fat than body mass index (BMI). BMI just measures how heavy someone is for their height and includes lean muscle mass.
“Recently it was recognized that it is how much excess fat you have around your organs that increases your risk of serious health conditions, such as heart disease, type 2 diabetes and certain cancers,” Eliasziw says. Excessive visceral fat in the abdomen triggers the release of cytokines such as IL-1 beta, which tend to encourage inflammation. IL-1 beta is the root of a cascade of reactions in the body that lead to cardiovascular disease, dementia, and other diseases of the circulatory and metabolic systems.
“In the initial analysis, there was no association between HEPA filtration and cytokines. But in people who had excessive visceral fat, there was a strong IL-1 beta connection,” Brugge says. People who are lean and healthy are not likely to get much benefit from HEPA filters. But individuals with excessive visceral fat probably will.
Brugge, Eliasziw, and their colleagues also looked at blood pressure and cognitive performance and found a similar pattern; not everyone benefited, but those who had elevated blood pressure or were older did.
Because commercial HEPA filters can be quite expensive, it’s useful for people to know whether they would likely benefit before spending money to buy and run one. Brugge and Eliasziw are now beginning a clinical trial in Hartford and Boston testing inexpensive homemade air filters made of 4 air filters and a box fan, which have been used successfully in other situations.
This study was funded by the National Institute of Environmental Health Sciences and the UConn School of Medicine.
Journal
American Journal of Preventive Cardiology
Method of Research
Experimental study
Subject of Research
People
Article Title
Pro-inflammatory cytokines moderated by visceral adiposity from a pragmatic randomized crossover trial of portable HEPA air purifiers
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