In a new study reported in Human Brain Mapping, people who smoked had three times greater risk of developing chronic back pain than non-smokers.Pascal Maramis/Flickr

Continuous exposure to passive smoking at childhood can increase the risk of heart attacks or strokes later in life, a new study says.

As a proof, researchers from Tasmania, Australia and Finland identified permanent damages in arteries of children being exposed to their parents' smoke. They said that the increased carotid intima-media thickness (IMT) or thickening of the innermost layers of the artery wall caused by exposure to passive smoking can place the children at greater risk of many heart problems in adulthood. Carotid intima-media thickness (IMT) has long been linked to atherosclerosis, a condition that poses risk to the heart.

Elasticity of the arteries is crucial for keeping the heart healthy. However, sometimes, a build-up of fatty deposits in the artery walls, leads to thickening of the walls, narrowing and damaging its elasticity and thus reducing flow of blood through them.  The occurrence can increase the risk of blood clots, strokes, heart failure, high blood pressure, renal failure, leg pains and aneurysm (swelling of blood vessels).

The study looked at 3,776 children, aged between three and 18, part of two studies from Finland (Cardiovascular Risk in Young Finns Study)and Australia (Childhood Determinants of Adult Health study). During the study, smoking habits of the parents were recorded. When the children grew up and reached adulthood, with the help of ultrasound, researchers measured thickness of their artery walls.  Carotid IMT was 0.015 mm thicker in children who's parents smoked. However, the study couldn't find any such adverse health effects associated with single parent smoking.

"Our study shows that exposure to passive smoke in childhood causes a direct and irreversible damage to the structure of the arteries," Dr Seana Gall, a research fellow in cardiovascular epidemiology at the Menzies Research Institute Tasmania and the University of Tasmania, said in a news release.

"We think that the effect was only apparent with both parents smoking because of the greater overall dose of smoke these children were exposed to," Dr Gall, added later.

Findings of the study have been reported in the European Heart Journal.

It is estimated that nearly 852 million people around the world use tobacco.  According to the World Health Organization (WHO), tobacco claims about 6 million lives every year and six lakh of the deaths are caused by exposure to second-hand smoke. Second-hand smoke contains more than 4,000 toxic chemicals and breathing smoke-filled air has been linked to sudden infant death syndrome (SIDS), asthma, meningitis, cough, cold and middle ear diseases, invasive meningococcal disease and even cancer.