Smoking may damage body's blood pressure autocorrect system

People who smoke take note! Smoking may increase the risk of developing hypertension, impairing body's blood pressure autocorrect system, a recent study suggests.

The study was published in the 'Journal of Physiology-Regulatory, Integrative and Comparative Physiology'.

"The human body has a buffering system that continuously monitors and maintains healthy blood pressure," said Lawrence Sinoway, director of the Penn State Clinical and Translational Science Institute.

"If blood pressure drops, a response called muscle sympathetic nerve activity (MSNA) is triggered to bring blood pressure back up to normal levels," Sinoway said.

An additional system -- called the baroreflex -- helps correct if blood pressure gets too high, he added.

According to Sinoway, the study found that after a burst of MSNA, the rise in blood pressure in a chronic smoker was about twice as great as in a non-smoker, pushing blood pressure to unhealthy levels.

"When the sympathetic nervous system fires, like with MSNA, your blood pressure rises and then a series of things happen to buffer that increase, to try to attenuate it. We think that in smokers, that buffering -- the baroreflex -- is impaired," Sinoway said.

Jian Cui, associate professor of medicine, said the results suggested that this impairment may be connected to hypertension.

"The greater rise in blood pressure in response to MSNA may contribute to a higher resting blood pressure level in smokers without hypertension. It's possible that this higher response to MSNA could also contribute to the eventual development of hypertension," Cui said.

For the study, the researchers recruited 60 participants -- 18 smokers and 42 non-smokers. None of the participants had hypertension. The smokers reported smoking an average of 17 cigarettes a day over a period of about 13 years.

To measure MSNA, the researchers inserted an electrode into the peroneal nerve, which sits below the kneecap, of each participant.

Additionally, they measured heart rate, diastolic and systolic blood pressure, and mean arterial pressure at the brachial artery in the upper arm.

After analysing the data, the researchers found no difference in systolic blood pressure between smokers and non-smokers. However, diastolic blood pressure, mean arterial pressure and heart rate were significantly higher in smokers. Smokers also had higher levels of MSNA. In addition, resting heart rate was significantly higher in smokers.

"Our study reveals another mechanism by which habitual smoking may contribute to the development of hypertension," Cui said.