Inhaled smoke shifts male cardiovascular system into overdrive

Secondhand tobacco smoke and smoke from cooking oil and wood smoke affected cardiovascular function of men and women who were exposed to small doses of the smoke for as little as 10 minutes, according to a study from the University of Kentucky.

The study confirmed previous findings that tobacco smoke could possibly harm cardiovascular function. In addition, it extended those findings by showing that:

• cardiovascular responses during brief exposures were similar to those found during longer or higher-level exposures
• the response occurs with different types of smoke (tobacco, cooking oil and wood smoke)
• men respond to environmental tobacco smoke with a greater increase in indexes of sympathetic outflow to blood vessels than do women

The sympathetic nervous system produces the "fight or flight" response, which drives the heart and blood pressure and may cause damage if activated too long. Women respond with a greater parasympathetic response, dubbed "rest and digest," which acts as a brake on the heart and blood pressure.

The study, Autonomic responses of men and women to particulate exposures, was conducted by Joyce McClendon Evans, Abhijit Patwardhan, Ashwin Jayanthi and Charles Knapp of the University of Kentucky; Roger Jenkins and Ralph Ilgner of the Oak Ridge National Laboratory; and Eric Hartman of CustomKYnetics, Inc. Ms. Evans will present the findings during the 122nd annual meeting of The American Physiological Society (www.the-aps.org/press), which is part of the Experimental Biology 2009 conference. The meeting will take place April 18-22 in New Orleans.

Controlled smoke exposures

Accumulating evidence indicates that an increase in air pollution is associated with an increase in heart attacks and deaths. These pollutants, including tobacco and cooking oil smoke, contain fine particles that evoke responses from heart and blood vessels indicating effects on their function.

This study briefly exposed people to low levels of common pollutants and measured their cardiovascular and cardiorespiratory responses. Forty healthy non-smokers (21 women, 19 men) whose average age was 35 participated in the experiment. The researchers exposed the participants to secondhand cigarette smoke, wood smoke or cooking oil smoke in separate trials as they sat in a 10-by-10-foot environmental chamber. The researchers cleared the air in the chamber after each trial.

They measured respiratory and cardiovascular function, including heart rate variability, breathing and blood pressure. These measures, in turn, gave researchers a picture of how the heart, circulatory and respiratory systems were reacting to the pollutants.

Results

The study found that, particularly among men, exposure to smoke changed breathing patterns, raised blood pressure oscillations in peripheral arteries and shifted control of heart rate toward sympathetic domination. The sympathetic nervous system becomes active during times of stress, but can cause harm to the heart and blood vessels if activated too often or too long.

Women did not have a strong sympathetic response to the pollutants, a healthier response in the face of frequent exposure. That men would respond differently is not a surprise: women tend to have stronger parasympathetic responses, which are more protective of the cardiovascular system, Ms. Evans said.

These results confirm results from earlier studies, but with exposures that were at lower levels and for shorter lengths of time. The study also extended the findings in several ways, including finding that men and women respond differently.

"I was surprised we got statistically significant results with this low level of exposure," Ms Evans said. "If we can detect these effects with smaller exposures, then the public health hazard from cigarettes and other particulate exposures may have been underestimated."