Secondhand smoke bad for heart

People who breathe in a lot of secondhand smoke (SHS) are twice as likely to die from heart disease as those exposed to lower levels.

Existing evidence suggests there is an association between SHS and risk of heart disease, although the reasons behind the association remain poorly understood. To investigate this, researchers examined 13,443 people living in England and Scotland, aged around 55 years. They measured salivary cotinine (an objective marker of SHS exposure) and biomarkers for heart disease - C-reactive protein (CRP) and fibrinogen. The participants were followed up for an average of 8 years, keeping track of those who developed heart disease and / or died.

Over the course of the study, 32 out of about 1,500 people who had never smoked but were exposed to high levels of secondhand smoke died of heart disease, compared to 15 out of about 1,000 never-smokers with low exposure levels. In analyses restricted to never-smokers, high secondhand smoke exposure was associated with more than a two-fold higher risk of dying from heart disease. They also found that that those with high exposure levels to SHS had higher levels of inflammatory markers (CRP and fibrinogen) in the body, a known risk factor for heart disease.

A high level of exposure would be equivalent to living with a smoker and getting exposed to secondhand smoke nearly every day. About 1 in 5 of the people in the study had high exposure levels, according to the saliva test. People exposed to a lot of secondhand smoke, as well as smokers themselves, were younger and more likely to be male, worse off financially, and less physically active than people with low exposure. But even when controlling for these potentially confounding factors, the link between secondhand smoke exposure and heart disease remained.

The findings add to the growing body of evidence linking secondhand smoke to heart disease.

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