The principles we espouse on Science-Based Medicine are vitally important, but some of the subjects we address are not so important in the big scheme of things. Homeopathy and electrodermal diagnostic devices don’t actually harm very many people. For today’s post, I’m going to follow the Willie Sutton rule and go where the money is, so to speak.
Smoking is the leading preventable cause of death. No prospective double blind randomized controlled studies have been done, or ever could be done; but a mountain of evidence converging from many avenues has established the health dangers of smoking beyond any doubt. Hill’s criteria of causation have been amply fulfilled. Smoking causes 90% of all deaths from lung cancer and chronic obstructive pulmonary disease (COPD). It increases the risk of coronary heart disease, stroke, several types of cancer, infertility, stillbirth, sudden infant death syndrome (SIDS), osteoporosis, and premature skin aging (wrinkles). The dangers of second-hand smoke have been amply documented, and where smoke-free laws have been passed there has been a drop in the incidence of heart attacks and of emergency room visits for children with asthma.
Two new studies published in The New England Journal of Medicine reinforce what we already knew and offer both good news and bad news.
Historical Notes
Back in 1604, King James I of England had a poor opinion of smoking. He said it was:
A custom loathsome to the eye, hateful to the nose, harmful to the brain, dangerous to the lungs, and in the black, stinking fume thereof, nearest resembling the horrible Stygian smoke of the pit that is bottomless.
He didn’t have any scientific evidence to go on, and neither did scientists until well into the 20th century. In the early 1900s, doctors promoted cigarette smoking. Ads featured doctor endorsements like “good for your health” and “more doctors smoke Camels.” Celebrities, Santa, even babies appeared in tobacco ads. The evidence of harm gradually accumulated, and the tide turned in 1964 with the Surgeon General’s report on smoking and health. Public attitudes changed, and the health hazards of smoking are now widely recognized, but the allure of cigarettes and the addictive properties of nicotine have kept the custom alive.
One New Study
A new study by Jha et al. found that smoking causes 25% of deaths among both men and women smokers between the ages of 35 and 69. Three times as many smokers die compared to nonsmokers. Smokers lose at least one decade of life expectancy. It’s hard to understand why anyone would knowingly begin using an addictive drug that would cut their life short by 10 years, but there’s something attractive about cigarettes that apparently overrides better judgment. Between 1965 and 2010 the prevalence of cigarette smoking in the US dropped from 42% to 19%, but it changed little from 2004 to 2010.
It’s a global problem. Most of the world’s smokers live in low- and middle-income countries. It is estimated that smoking will kill about 1 billion people in the course of the 21st century. That’s bad news.
The good news is that if smokers stop smoking before the age of 40, their risk of death will drop by 90% compared to those who continue to smoke. [Clarification: smokers’ life expectancy is 10 years less than that of non-smokers. If they stop smoking before the age of 40, their life expectancy will improve to only one year less than that of never-smokers.] It’s never too late to stop, but the benefits diminish with age. Smokers who stop at age 45-54 gain 6 years of life, and those who stop at age 55-64 gain 4 years of life.
Another New Study
A second study by Thun et al. looked at trends in smoking-related mortality over different time periods and found that:
The risk of death from cigarette smoking continues to increase among women and the increased risks are now nearly identical for men and women, as compared with persons who have never smoked. Among men, the risks associated with smoking have plateaued at the high levels seen in the 1980s, except for a continuing, unexplained increase in mortality from COPD.
For women, the relative and absolute risks of death from smoking have risen to parity with men for lung cancer, COPD, ischemic heart disease, and stroke. “You’ve come a long way, baby” but now maybe you will wish you hadn’t. As the authors point out, “women who smoke like men die like men.” And it appears that women have more difficulty quitting than men.
They corroborated the findings of the Jha study that smokers are 3 times as likely to die. [Clarification: over the 10 year period studied, all-cause mortality was at least three times as high among current smokers as among those who had never smoked.] More than two thirds of all deaths among current smokers in the older age groups are associated with smoking. The rate of COPD in nonsmokers has declined, but it continues to rise in smokers. The reason for that rise is not clear. They speculate that changes in cigarette design (less irritating tobacco blends, paper that dilutes the smoke, etc.) may have led to easier and deeper inhalation.
What Can Be Done?
Smoking is the leading preventable cause of death. What can we do about it? Prohibition wouldn’t work any better than it did for alcohol. But legislation to raise taxes on cigarettes, prohibit sales to minors, and restrict smoking in public places can have an impact. Warning labels on cigarette packages increase public awareness but don’t persuade many smokers to quit. Smoking cessation programs using nicotine replacement, drugs, hypnosis, incentives, and social interventions don’t have a very high long-term success rate. But there is hope: three-quarters of ex-smokers report having quit on their own without assistance of any kind.
Over 68% of smokers say they want to stop. . Advice from a health professional increases quit attempts and increases use of effective medications which can nearly double to triple rates of successful cessation. The US Preventive Services Task Force (USPSTF) recommends (Grade A recommendation) that clinicians ask all adults about tobacco use and provide tobacco cessation interventions for those who use tobacco products. But less than half of smokers who saw a health professional in the last year reported receiving advice to quit. That’s shameful. It means doctors were treating lesser problems while ignoring the greatest modifiable threat to their patients’ health. Surely we can do better.
This article was originally published in the Science-Based Medicine blog.
