Have We Killed Half of our Soldiers with Cigarettes?

Two long-term studies yield grim stats, and women are no exception.

We know that smoking kills. But until the results of 50 years’ worth of observations on British male smokers was published by Richard Doll and coworkers in the British Journal of Medicine in 2004, we didn’t know how many.  Cigarettes will kill at least half of those who smoke them past the age of 30—possibly more. In older, specific populations, possibly as many as 2/3.

It took a prospective study of more than 34,000 British doctors, starting in 1951 and ending in 2001, to establish the grim parameters with some degree of precision. As the study authors of the 2004 summary paper put it: “A substantial progressive decrease in the mortality rates among non-smokers over the past half century… has been wholly outweighed, among cigarette smokers, by a progressive increase in the smoker v non-smoker death rate ratio due to earlier and more intensive use of cigarettes.” In other words, the great reduction in disease mortality rates achieved in the 20th Century, courtesy of better prevention and treatment, effectively never happened for long-term male smokers. Smoking in Britain and America took off in a major way between the two world wars, and sufficient time has now passed to conclude that “men born in 1900-1930 who smoked only cigarettes and continued smoking died on average about 10 years younger than lifelong non-smokers.”

As for women, it took a few decades longer to nail down the truth, because women did not begin smoking in peak numbers until the 1960s. While men born between 1900 and 1930 took to cigarettes in a big way, women born around 1940 were the first cohort of female smokers to consume a substantial number of cigarettes throughout their adult lives. This 20-year lag is crucial, because it means that solid numbers for female mortality rates require solid figures on mortality rates in the 21st Century. And now we have them, courtesy of the Million Women Study in the UK. The results were recently published in The Lancet by Kirstin Pirie and others. They are just as bad as you might have guessed, putting women on a firm equal footing with their male counterparts when it comes to smoking deaths.

The Million Women Study, a database originally used for the UK’s National Health Service Breast Screening Program, recruited female volunteers between the ages of 50 and 69. The figures were eerily similar to those from the earlier study of male British doctors: “If combined with 2010 UK national death rates, tripled mortality rates among [female] smokers indicate 53% of smokers and 22% of never-smokers dying before age 80 years, and an 11-year lifespan difference…. Although the hazards of smoking until age 40 years and then stopping are substantial, the hazards of continuing are ten times greater.” In this study, the researchers found little difference between female smokers and nonsmokers when it came to confounding variables like weight, blood pressure, or lipid profile. A four-year head start—beginning to smoke at the age of 15 rather than 19, say—can put women at a measurably greater risk for lung cancer deaths.  And a little goes a long way: “Even those smoking fewer than ten cigarettes per day at baseline had double the overall mortality rate of never-smokers.” Low-tar won’t save them, either. “Low-tar cigarettes are not low-risk cigarettes,” the investigators write, “and the Million Women Study shows that more than half of those who smoke them will eventually be killed by them, unless they stop smoking in time to avoid this.”

There it is again: Half of all smokers are going to die from smoking.  As the authors of the Lancet study wrote: “If women smoke like men, they die like men.”

In summary, those who stop smoking at age 50 gain about six years of life expectancy. Quit at 40, and you get an extra nine years. A non-smoker’s chances of living from 70 to 90 are three times higher than a smoker’s. The researchers found that the doctors who stopped smoking by age 30 managed to avoid almost all of the lifespan penalties associated with smoking—primarily lung cancer, COPD, and heart disease. (Only about 3% of smoking deaths are due to fires, accidents, poisonings, etc.). And even lifelong smokers who do not quit until the age of 60 are still rewarded with an extra three years of life span, on average.

Perhaps the saddest thing about the findings is the ways in which they suggest that British and American military commanders may have been sentencing countless numbers of soldiers to death for decades, through the simple act of giving away cigarettes in K-rations, and selling them cheaply in other circumstances. As the report in the British Medical Journal states, “widespread military conscription of 18 year old men, which began again in 1939 and continued for decades, routinely involved provision of low cost cigarettes to the conscripts. This established in many 18 year olds a persistent habit of smoking substantial numbers of manufactured cigarettes, which could well cause the death of more than half of those who continued.” In a perverse reminder of the Agent Orange scandal in Vietnam, American and British military command may have exposed their soldiers to a much greater threat, for a much longer period, with worse odds for survival.

One obvious confounding variable in such studies is alcohol. It requires a sensitive statistical analysis to work through correlations between drinking, smoking, and, say, liver disease.  But “the large majority of the excess overall mortality among smokers is actually caused by smoking,” the Lancet researchers maintain with confidence.  The overall point seems clear: These long-term results show that the risks from continual cigarette smoking are even greater than we thought.

The dismal bottom line of the two smoking studies is that we appear to be right on schedule for meeting the UN’s prediction of one billion tobacco deaths in this brave new century.

Pirie, K., Peto, R., Reeves, G., Green, J., & Beral, V. (2012). The 21st century hazards of smoking and benefits of stopping: a prospective study of one million women in the UK The Lancet DOI: 10.1016/S0140-6736(12)61720-6

Photo Credit: Ianier67 via Creative Commons.

Smoking and Adolescent Attention Deficit

Are young smokers risking cognitive impairment as adults?

 Call it “nicolescence.” It’s that time of life when certain 18-and-unders discover cigarettes. Most adult smokers begin their habit before the age of 19, and a majority of adolescents have tried cigarettes at least once. But for some of them—those who were “born to smoke,” in a sense—early exposure to nicotine may influence adolescent cognitive performance in ways that adult exposure to nicotine does not. Furthermore, early exposure may result in “cognitive impairments in later life.”

These provocative notions are raised by a group of researchers at VU University, Amsterdam, The Netherlands, in a paper for Nature Neuroscience. And while the specifics of glutamate activity they have documented are fascinating, the leaps back and forth between adolescent humans and adolescent lab mice are dizzying. Nonetheless, the bold claims made in the paper prompted the scientists “to reconsider our views on the etiology of attention deficits.”

That may be more than many addiction researchers are willing to countenance, but the study makes an intriguing case for long-term effects on attentional processing. The Dutch researchers exposed adolescent rats to nicotine, assessed visuospatial attention and other markers associated with synaptic activity in the prefrontal cortex, and found impaired measures of attention and signs of increased impulsivity in adulthood after five weeks of abstinence. Adult rats exposed to nicotine for the first time did not show similar long-term consequences.

The molecular underpinnings for this phenomenon appear to be reduced glutamate receptor protein levels in the prefrontal cortex. Glutamate is a neurotransmitter involved in attention, among other cortical tasks. Glutamate levels were “altered specifically by adolescent and not adult nicotine exposure” in the lab animals, the researchers found.

The glutamate receptor mGluR2 is the likely culprit.  The researchers report that “a lasting downregulation of mGluR2 on presynaptic terminals of glutamatergic synapses in the prefrontal cortex persists into adulthood causing disturbances in attention…. Restoring mGluR2 activity in vivo in the prefrontal cortex of adult rats exposed to nicotine during adolescence remediated the attention deficit.”

The study concludes: “Not only from a behavioral, but also from a molecular point of view, the adolescent brain is more susceptible to consequences of nicotinic receptor activation.” In other words, there is at least some evidence that the neurotoxic effects of nicotine are potentially more severe in the early developmental stage called adolescence.

The Dutch study is not the only one of its kind. In 2005, Biological Psychiatry published a report on cognition in which adolescent smokers “were found to have impairments in accuracy of working memory performance irrespective of recency of smoking. Performance decrements were more severe with earlier age of onset of smoking.”

And a 2007 study published in Neuropsychopharmocology, based on testing and fMRI scans of 181 male and female adolescent smokers, concluded that “in humans, prenatal and adolescent exposure to nicotine exerts gender-specific deleterious effects on auditory and visual attention…” Boys were more sensitive than girls to attention deficits involving auditory processing, while girls tended to show equal deficits in both auditory and visual attention tasks. 

Counotte, D., Goriounova, N., Li, K., Loos, M., van der Schors, R., Schetters, D., Schoffelmeer, A., Smit, A., Mansvelder, H., Pattij, T., & Spijker, S. (2011). Lasting synaptic changes underlie attention deficits caused by nicotine exposure during adolescence Nature Neuroscience DOI: 10.1038/nn.2770

Photo Credit: http://smoking-quit.info/