As little as 30 minutes of secondhand smoke can lead to hardening of the arteries in non-smokers, Japanese researchers reported at the American Heart Association (AHA) meeting.

While most people know that secondhand smoke can affect those living or working around the smoker, most say that damage only occurs with long-term exposure.

However, Japanese researchers report changes that can lead to heart disease occur in as little as 30 minutes.

“Exposure to second-hand tobacco smoke can result in reduced blood flow and an increase in a marker for oxidative stress equivalent to what occurs in smokers,” says Toru Kato, MD, of the faculty of medicine at Saga University in Saga, Japan.

Thirty healthy male Japanese men — 15 smokers and 15 non-smokers — were exposed to passive smoke for a 30-minute period. The researchers looked for the percentage of artery narrowing and for a marker of oxidative stress, which can damage cells in the body’s vessels and lead to atherosclerosis (hardening of the arteries).

What the researchers found was that the arterial blood flow was lower and oxidative stress was higher in smokers than in non-smokers at the beginning of the study. However, after 30 minutes of exposure to secondhand smoke, the levels in non-smokers mimicked that of long-term smokers.

“Second-hand smoke is dangerous,” Kato tells WebMD. “Thirty minutes is enough to produce damage, but repeated exposure is even more dangerous.”

Lynn Smaha, MD, PhD, past president of the AHA and a cardiologist with the Guthrie Clinic in Sayre, Pa., says, “We have known for a long time that nicotine is hazardous to your health. These [results] show that even a 30-minute exposure can be hazardous to the lining of the blood vessels.”

It is not like being in a bar where people have been smoking for hours, he says. “Just 30 minutes makes a difference. This study narrows the timetable and documents the affect with scientific markers.”

By Linda Little, reviewed by Louise Chang, MD

SOURCES: American Heart Association Scientific Sessions, Dallas, Nov. 14-16, 2005. Toru Kato, MD, faculty of medicine, Saga University, Saga, Japan. Lynn Smaha, MD, PhD, past president, American Heart association; cardiologist, Guthrie Clinic, Sayre, Pa.