Children who are exposed to secondhand smoke for long periods may face an increased risk of dying from lung disease later in life, a new study suggests.

Chronic obstructive pulmonary disease (COPD) is Ireland's fourth biggest killer and currently affects an estimated 380,000 people here.

It is an umbrella term for a number of chronic lung disorders, including bronchitis and emphysema. COPD is a progressive, disabling condition caused by a narrowing of the airways, and smoking is the main cause.

However while it is already known that secondhand (passive) smoke has an adverse effect on the lungs of both adults and children, until now, it was unclear whether childhood exposure to secondhand smoke was linked with mortality (death) in adulthood.

US researchers decided to investigate this further. They looked at almost 71,000 non-smoking men and women aged between 50 and 74, over a 22-year period.

The study found that the mortality rate from COPD of those who had lived with a daily smoker throughout childhood, was 31% higher when compared with those who had lived with non-smokers.

While the researchers only looked at deaths, they believe that the findings suggest that living with a smoker during childhood could also increase the risk of non-fatal COPD.

The study also found that those who were exposed to secondhand smoke as adults (10 or more hours per week), had a 9% increased risk of dying from all causes, a 23% increased risk of dying from stroke, a 27% increased risk of dying from heart disease and a 42% increased risk of dying from COPD.

"This is the first study to identify an association between childhood exposure to secondhand smoke and death from COPD in middle age and beyond. The results also suggest that adult secondhand smoke exposure increases the risk of COPD death. Overall, our findings provide further evidence for reducing secondhand smoke exposure throughout life," commented cancer epidemiologist, W.Ryan Diver.

Details of these findings are published in the American Journal of Preventive Medicine.