16 October 2009

Smog tougher on the obese

Air pollution appears to hit the obese hardest, causing significant increases in blood pressure, a new study finds.


Air pollution appears to hit the obese hardest, causing significant increases in blood pressure, a new study finds.

Air pollution has been linked to a variety of health problems including asthma, heart disease and diabetes, but this is the first time obesity has been taken into account, researchers say.

"For those who are obese, exposure to air pollution further exacerbated systolic blood pressure and pulse pressure," said lead researcher Srimathi Kannan, an assistant professor at the School of Public Health and Health Sciences of the University of Massachusetts, US.

"When you are looking at environmental exposures and medical outcomes, you have to consider obesity," Kannan said.

The report is published in the Journal of Epidemiology and Community Health.

How the study was conducted
For the study, Kannan and colleagues collected data on air pollution and health as part of the Healthy Environments Partnership study. The study looked at these factors in 919 households in areas of Detroit that included rich and poor neighborhoods and a mix of racial and ethnic groups.

Among the 348 people who had their blood tested and their weight, blood pressure, height and waist circumference measured, over half were obese and 57% had waist circumferences that put them at risk for diabetes and heart disease.

Among all those tested, 68% had high blood pressure or were on the edge of developing high blood pressure and 36% had high cholesterol, the researchers found.

Average levels of particulate matter air pollution were 15 micrograms per cubic meter in three of the places measured, but in one area the levels were 20% higher.

People who lived in the area with the greatest amount of air pollution had higher pulse pressure than those in other areas, the researchers found. Pulse pressure is the difference between the systolic and diastolic blood pressure, the top and bottom numbers in a reading.

In addition, people living in the smoggiest areas also had higher systolic blood pressure, and it didn't matter whether they were obese or of normal weight. However, the effect was greater among the obese, Kannan's team noted.

Combined threat
The researchers believe that individuals and society need to address the combined health threat of obesity and air pollution.

"Continued vigilance regarding regulation of emissions sources in communities of colour and low-income communities is critical, combined with efforts to address obesity, in order to reduce well-established disparities in cardiovascular health," the researchers concluded.

Michael Jerrett, an associate professor of environmental health sciences at the School of Public Health of the University of California at Berkeley, said the study "is linking into the broader debates about underlying causes of death in our society."

For people who already have high blood pressure, diabetes or who are obese, air pollution may make these conditions worse, Jerrett said. "You end up with this vicious cycle where someone becomes obese due to lifestyle and other factors, which actually becomes worsened by the air pollution," he said.

More effects of air pollution
Jerrett noted that air pollution is only one environmental factor that contributes to worsening health. In addition, the poor are often exposed to more air pollution because of the neighborhoods they live in, he added. "What comes along with the social deprivation is a cascade of other lifestyle and occupational factors that may also make the person more susceptible to air pollution's effects," he said.

Those factors can include poor nutrition, stress, traffic and industrial noise, Jerrett explained. "These can be heightening their sensitivity to air pollution," he said. "So many of these susceptibility factors cluster together in the same neighborhood, in the same person." - (Steven Reinberg/HealthDay News, October 2009)

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