Not all heart disease patients know that secondhand smoke is bad for them – and not all doctors are asking them if they live with a smoker, according to a new study.

“Physicians have not been trained to ask patients routinely about secondhand smoke exposure,” said coauthor Dr. Nancy A. Rigotti of the Tobacco Research and Treatment Center at Massachusetts General Hospital in Boston.

This is a gap in practice that needs to be addressed, she said.

Rigotti suspects that this finding is true for most adult medical care. Pediatricians are much more likely to ask about smoking in the home because the harms to children are well known, she told Reuters Health by email.

Coronary heart disease (CHD), in which plaque builds up inside the arteries supplying blood to the heart, is the most common type of heart disease and kills about 380,000 people each year in the U.S., according to the Centers for Disease Control and Prevention.

Secondhand smoke exposure can increase a nonsmoker’s risk for heart disease by 25 to 30 percent, Rigotti and her coauthors write. People hospitalized for heart disease should avoid secondhand exposure when they are discharged.

“It is not as big a risk factor as being a smoker oneself, but it is still a risk,” Rigotti said.

For the new study, researchers interviewed 214 adults hospitalized for CHD at Massachusetts General Hospital, asking about their smoke exposure history.

More than 20 percent said they had been exposed to secondhand smoke within the past 30 days, and 15 percent said they had been exposed to smoke within the week before hospital admission. Almost 14 percent said they lived with a smoker, usually a spouse or child.

Two-thirds of the patients reported having a ‘smoking ban’ in their home and a similar number had forbidden smoking in the car.

Though most said that secondhand smoke is harmful, only 56 percent believed it increased nonsmokers’ risk of heart attack, while the rest believed it increases risk only slightly or did not know. They largely felt the same way about their own risk of heart attack, according to results in JAMA Internal Medicine.

Only 37 patients remembered being asked about secondhand smoke exposure by a doctor or nurse since hospital admission, 21 were asked if they lived with a smoker, and three had been advised to keep their home or car smoke-free.

“Even though it looks like a lot of people understand that secondhand smoke is a bad thing and a lot of health workers understand, too, it’s not being addressed,” said Dr. R. William Vandivier of the University of Colorado Department of Medicine in Aurora, who wrote an accompanying commentary in the journal.

“People aren’t asking the questions, if they do ask they’re not doing anything about it,” he told Reuters Health by phone.

This should be a subject for discussion when patients are hospitalized or at a doctor’s office visit, and the doctor, nurse or any other ancillary staff may be involved too, he said.

“If enough people say it, eventually they’re going to get it,” Vandivier said.

According to previous studies, if a doctor spends as little as three minutes talking about the dangers of smoking, that can lead to patients changing their behavior he said.

One reason providers may forget to ask about secondhand smoke is the lack of a prompt or place to record the answer in some electronic medical records systems, he noted.

Once a patient reports secondhand smoke exposure, he or she could be counseled about cleaning up the home environment or instituting smoking bans in houses and cars, but there is no established protocol for that, he said.

“The ideal is to encourage and help the smoker to quit,” Rigotti said. “Until that happens, there should be a policy that no one ever smokes in either the car or the home.”

There should never be smoking in an enclosed space, she said. Any provider can ask about this, but having a doctor do it may convey more importance to the problem, she added.

“I don’t think anyone knows the exact solution but we need to figure something out,” Vandivier said.