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More than 600,000 deaths per year worldwide -- 1 perecent of all deaths -- caused by passive smoking, and around 165,000 of these deaths are among children

Lancet

Around one in 100 deaths worldwide each year is due to passive smoking, which causes more than 600,000 people to die each year worldwide. Some 165 000 of these deaths are among children. These are the conclusions of an Article published Online First and in an upcoming edition of The Lancet, written by Dr Annette Prüss-Ustün, WHO, Geneva, Switzerland, and colleagues. The study is the first to assess the global impact of second-hand smoke.

In order to attain consistency for comparison, the authors used data from 2004 for their analysis, since this was the last year to have comprehensive data across the 192 countries studied. They estimated both deaths and years lost of life in good health (DALYs).

Worldwide, 40% of children, 33% of male non-smokers, and 35% of female non-smokers were exposed to second-hand smoke in 2004. This exposure was estimated to have caused 379 000 deaths from ischaemic heart disease, 165 000 from lower respiratory infections, 36 900 from asthma, and 21 400 from lung cancer. 603 000 deaths were attributable to second-hand smoke in 2004, which was about 1•0% of worldwide mortality. 47% of deaths from second-hand smoke occurred in women, 28% in children, and 26% in men. DALYs lost because of exposure to secondhand smoke amounted to 10•9 million, which was about 0•7% of total worldwide burden of diseases in DALYs in 2004. 61% of DALYs were in children. The largest disease burdens were from lower respiratory infections in children younger than 5 years (5 939 000/54%), ischaemic heart disease in adults (2 836 000/26%), and asthma in adults (1 246 000/11%) and children (651 000/6%).

While deaths due to passive smoking in children were skewed towards low-income and middle-income countries, deaths in adults were spread across countries of all income. For example, in the high-income countries of Europe (Europe Zone A), only 71 child deaths occurred, while 35 388 deaths occurred in adults. Yet across the countries of Africa assessed, an estimated 43 375 deaths due to passive smoking occurred in children, compared with 9514 in adults. The authors say: "Two-thirds of these deaths occur in Africa and south Asia. Children's exposure to second-hand smoke most likely happens at home. The combination of infectious diseases and tobacco seems to be a deadly combination for children in these regions and might hamper the efforts to reduce the mortality rate for those aged younger than 5 years as sought by Millennium Development Goal 4."

Worldwide, children are more heavily exposed to second-hand smoke than any other age-group, and they are not able to avoid the main source of exposure--mainly their close relatives who smoke at home. The authors note that smoke exposure in a home where somebody smokes appears similar across most regions, although more intense in Asia and the Middle East. Furthermore, children are the group that has the strongest evidence of harm attributable to second-hand smoke. These two factors should form the basis of public health messages and advice to policy makers.

Almost two-thirds of all deaths due to passive smoking in children and adults and a quarter of DALYs attributable to exposure to second-hand smoke were caused by ischaemic heart disease in adult non-smokers. Smoke-free laws banning smoking in indoor workplaces rapidly reduce numbers of acute coronary events. The authors say: "Policy makers should bear in mind that enforcing complete smoke-free laws will probably substantially reduce the number of deaths attributable to exposure to second-hand smoke within the first year of its implementation, with accompanying reduction in costs of illness in social and health systems."

As noted above, the largest effects on deaths occurred in women. The absolute number of deaths is higher in women than in men for two main reasons. First, the number of female non-smokers (thus susceptible to be exposed to second-hand smoke by definition) is about 60% higher than that of male non-smokers (whereas there are many more male 'first-hand' smokers than women). Second, in Africa and some parts of the Americas, the eastern Mediterranean, and southeast Asia, women are at least 50% more likely to be exposed to second-hand smoke than are men.

These deaths should be added to the estimated 5•1 million deaths attributable to active smoking to obtain the full effect of both passive and active smoking. Smoking, therefore, was responsible for more than 5•7 million deaths every year in 2004. In their analysis, the authors assumed that those who already smoked 'first-hand' would not be further affected by second-hand smoke. Yet if the effects of second-smoke were similar on smokers as non-smokers, the number of deaths due to second-hand smoke would have been 30% higher.

Only 7•4% of the world population lives in jurisdictions with comprehensive smoke-free laws at present, and the enforcement of these laws is robust in only a few of those jurisdictions. In such locations, research has shown these laws reduce exposure to second hand smoke in high-risk settings such as bars and restaurants by 90%, in general by 60%. In addition to the protection they offer to non-smokers, such smoke-free policies reduce cigarette consumption among continuing smokers and lead to increased success rates in those trying to quit. The authors recommend immediate enforcement of WHO's Framework Convention on Tobacco Control, which includes higher tobacco taxes, plain packaging and advertising bans, among other factors.

The authors conclude: "Policy makers should also take action in two other areas to protect children and adults. First, although the benefits of smoke-free laws clearly extend to homes, protection of children and women from second-hand smoke in many regions needs to include complementary educational strategies to reduce exposure to second-hand smoke at home. Voluntary smoke-free home policies reduce exposure of children and adult non-smokers to second-hand smoke, reduce smoking in adults, and seem to reduce smoking in youths. Second, exposure to secondhand smoke contributes to the death of thousands of children younger than 5 years in low-income countries. Prompt attention is needed to dispel the myth that developing countries can wait to deal with tobacco-related diseases until they have dealt with infectious diseases. Together, tobacco smoke and infections lead to substantial, avoidable mortality and loss of active life-years of children."

In a linked Comment, Dr Heather L Wipfli and Dr Jonathan M Samet, Department of Preventive Medicine, Keck School of Medicine of USC, USC Institute for Global Health, University of Southern California, Los Angeles, CA, USA, say: "Although the social-norm change that comes with smokefree laws can spill over to homes, broad initiatives are needed to motivate families to put their own policies into place to reduce exposure to second-hand smoke at home. In some countries, smokefree homes are becoming the norm, but far from universally."

They conclude: "There can be no question that the 1•2 billion smokers in the world are exposing billions of non-smokers to second-hand smoke, a disease-causing indoor-air pollutant. Few sources of indoor-air pollution can be completely eliminated. However, smoking indoors can be eliminated--with substantial benefits, as shown by this new set of estimates."

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For contacts, please note: Dr Peruga is co-author within the Tobacco Free Initiative in WHO. In case of unavailability, Dr Sanda can address tobacco-related policy issues. Dr Prüss-Ustün is co-author in the Department of Public Health and Environment. Dr Woodward is co-author and based in New Zealand.

Dr Armando Peruga, WHO, Tobacco Free Initiative, Geneva, Switzerland. T) Mobile: +41 79 249 3504; direct: +41 22 791 1496 E) perugaa@who.int

Dr Luminita Sanda, WHO, Tobacco Free Initiative, Geneva, Switzerland. T) direct: +41 22 791 5495; Mobile: +41 79 20122 09 E) sandal@who.int

Dr Annette Prüss-Ustün, WHO, Tobacco Free Initiative, Geneva, Switzerland. T) direct: +41 22 791 3584; Mobile: +41 79 592 0117 E) pruessa@who.int

Dr Alistair Woodward, School of Population Health, University of Auckland, Auckland, New Zealand. T) +64 9 373 7599 ext 86361 E) a.woodward@auckland.ac.nz

Dr Heather L Wipfli, Department of Preventive Medicine, Keck School of Medicine, USC Institute for Global Health, University of Southern California, Los Angeles, CA, USA. T) +1 323 865-0411 E) hwipfli@usc.edu

For full Article and Comment, see: http://press.thelancet.com/smoking.pdf

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