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.

States Quietly Defunding Anti-Smoking Programs For Kids

Only 2 cents of each tobacco settlement dollar goes to smoking prevention plans.

If there’s one thing we know about smoking, it’s that for every smoker who quits, we gain a net financial benefit. These health cost savings can be huge for states, which is why all of them have put in place smoking cessation plans and programs for their citizens. And they are able to run this programs because of the monies that come to them under the 1998 master tobacco settlement.

Perhaps it doesn’t come as a huge surprise, but it’s depressing, all the same: The Campaign for Tobacco-Free Kids estimates that states will spend less than 2 per cent of these court-mandated funds on actual programs to prevent kids from smoking. The report accuses the states of failing to reverse budget cuts to “programs that have set back the nation’s efforts to reduce tobacco use.”

The report was undertaken to access whether states have been using the estimated $246 billion over 25 years—plus cigarette taxes—to reduce tobacco use. What they found was that “states have failed to reverse deep budget cuts that reduced funding for tobacco prevention by 36 percent” from 2008 to 2012. Only North Dakota and Alaska are currently funding smoking cessation programs at the level recommended by the Centers for Disease Control and Prevention (CDC). Four states—New Hampshire, New Jersey, North Carolina, and Ohio—have allocated ZERO funds for tobacco prevention programs in FY 2013.

“Given such a strong return on investment,” the report concludes, “states are truly penny-wise and pound-foolish in shortchanging tobacco prevention and cessation programs.” The report declined to speculate on where the money actually goes, but noted that this was the “second lowest amount states have spent on tobacco prevention programs since 1999, when they first received tobacco settlement funds.”

The cries of outrage came thick and fast:

“The states have an obligation to use more of their billions in tobacco revenues to fight the tobacco problem. Their failure to do so makes no sense given the evidence that tobacco prevention programs save lives and save money by helping reduce health care costs."—Matthew L. Myers, President of the Campaign for Tobacco-Free Kids

"States with comprehensive tobacco control programs experience faster declines in cigarette sales, smoking prevalence and lung cancer incidence and mortality than states that do not invest in these programs."—John R. Seffrin, CEO of the American Cancer Society Cancer Action Network

"The paltry amount of money that states spend on tobacco prevention and cessation programs is extremely disappointing…. These programs work and it’s time for states to put more skin in the game."—Nancy Brown, CEO of the American Heart Association

"Too many states are failing their citizens by abandoning their responsibility to invest in proven programs that prevent people from smoking and help smokers quit…. Supporting these programs at recommended levels is not only the right thing to do, it's the smart thing to do — quitting smoking or never starting saves lives and saves money."—Paul G. Billings, senior vice president of Advocacy & Education at the American Lung Association

In 2007, the CDC concluded: “We know how to end the epidemic. Evidence-based, statewide tobacco control programs that are comprehensive, sustained, and accountable have been shown to reduce smoking rates, tobacco-related deaths, and diseases caused by smoking.”

Two cents on every dollar. About 20 percent of Americans smoke. “Tobacco companies spend more than $18 to market tobacco products for every one dollar the states spend to reduce tobacco use.” What’s wrong with this picture?

Photo Credit: http://www.tobaccofreekids.org

Science, Academia, and Tobacco

A review of The Golden Holocaust: Origins of the Cigarette Catastrophe and the Case for Abolition

Part III

Academic collaborations come in many flavors. Just because the money is corporate doesn’t mean the studies that are funded are flawed by definition. But the cigarette industry’s academic philanthropy set new records for hubris, writes Robert Proctor, professor of history at Stanford University, in his new book, The Golden Holocaust. Duke University and Bowman Gray School of Medicine, both in North Carolina, are named for tobacco magnates.

Harvard has a long and dubious history of tobacco largesse.  Harvard’s Tobacco and Health Research Program kicked off in 1972 with a generous tobacco grant from the Tobacco Institute, who dreamed up the program in the first place. “The Harvard project made the industry look good and so was handsomely endowed, absorbing $7 million over an eight-year period.” Also in 1972, Harvard anthropologist Carl Seltzer testified for the industry in numerous public hearings, stating: “We do not know whether or not there is a causal relationship between smoking and heart disease.” In 2002, Harvard’s School of Public Health declared it would no longer undertake research sponsored by the cigarette industry. Many universities had already gone cold turkey, and after Harvard, bans were put in place by the Karolinska Institute, Johns Hopkins University, Emory University, and many others.

Proctor informs us that “Washington University in St. Louis has been another big sponge for tobacco money." In 1971, the university set a new world record for an industry grant to a single institution, and “millions more were eventually funneled into the School of Medicine, turning it into a hotbed of cigarette-friendly activism.” The irony of taking money from Big Tobacco to fund research on lung cancer is not lost on Proctor. A good deal of the research was aimed away from tobacco and toward possible causes like viruses. “The goal was clearly more than cancer cures,” he writes. “The industry also hoped to generate good PR and academic allies.” The industry was able to garner  sympathetic headlines, like “Helping in Fight against Cancer,” in the St. Louis Globe-Democrat.

The other academic hotbed thoroughly penetrated by Big Tobacco was UCLA, according to Proctor. “Tobacco collaborators at UCLA have attracted their fair share of criticism from public health advocates, and for understandable reasons.” The university picked up its own multimillion-dollar grant from cigarette makers for the Program on Tobacco and Health in 1974, and that wasn’t the first tobacco money the university had taken. “As with all such projects,” Proctor writes, “industry lawyers… played a key role in the decision to fund—with the companies also conceding that the decision ‘should be based more on public relations than on purely scientific grounds.’” The end came in 2007, when “UCLA’s dance with the devil” garnered a ton of unwanted press. Reports showed that UCLA had taken more than $6 million from Philip Morris for research “to compare how children’s brains and monkey brains react to nicotine.”

Proctor admits that singling out Harvard, Washington University and UCLA is somewhat misleading, “given that scholars throughout the world have gorged themselves on tobacco money. Indeed it may well be the rare institution that has NOT at one time or another dipped into this pot.”

Including Stanford, where Proctor teaches. Plenty of Stanford researchers have undertaken contract work and served as expert witnesses for the industry right in Proctor’s own backyard, where “at least eighteen faculty members have received monies (in the form of sponsored research) from the Council for Tobacco Research, with at least two of these—Judith Swain and Hugh McDevitt from the medical school—serving on its Scientific Advisory Board. Stanford pharmacologists were assisting the industry with its diethylene glycol studies as early as the 1930s…”

In the conclusion to his densely researched but surprisingly readable work, Proctor returns to the controlling irony of the book: “Our bizarre starting point is the well-stocked shelf of cigarettes, to which we respond by begging people not to purchase them.” He presents the dream of a world in which cigarettes have been abolished. To do so, he admits, would require a leap. “If phasing out tobacco seems out of reach, this is only because our imaginations are impoverished.” And he has scant patience for the “Prohibition failed” argument. It failed, he says, because people like to drink. “Tobacco presents us with a very different situation. Nicotine is not a recreational drug. Most people who smoke wish they didn’t, and most smokers (90 percent) regret ever having started.”

Graphics Credit: http://www.prwatch.org/node/7004

The Tobacco Industry as Disease Vector

A review of The Golden Holocaust: Origins of the Cigarette Catastrophe and the Case for Abolition

Part II

The famous Surgeon General’s Report of 1964, officially warning Americans about the dangers of smoking, and publicizing the cancer connection, is typically seen as a triumphal moment in American medical history. But according to Stanford history professor Robert Proctor in his book, The Golden Holocaust: Origins of the Cigarette Catastrophe and the Case for Abolition, the report was “flawed in a number of interesting respects.” [The author, above, with paraphernalia] For one thing, members of the advisory committee consulting on the report, many of them congressman friendly to the tobacco cause, succeeded in their attempts to have smoking referred to as a “habit” rather than as addiction—a shameful Orwellian turn that went uncorrected for 25 years.

Meanwhile, the industry continued to fund new institutes, and continued to give out research grants for “red herring” research. As an example, the highest-ranking officer of the American Heart Association received money from one of the industry’s fraudulent research arms.

As late as the early 80s, most smokers believed they suffered from a bad habit, rather than an addiction—even though a majority of them wished they didn’t smoke. That is an odd kind of consumer “choice.” Cigarette makers have spent millions to perpetuate this myth. Proctor views tobacco industry executives and lawyers as a unique form of disease vector, spreading the pernicious health consequences of smoking across the globe.

The 2008 World Health Organization (WHO) Report on the Global Tobacco Epidemic fleshes out this metaphor, suggesting that all epidemics have a means of contagion, “a vector that spreads disease and death. For the tobacco epidemic, the vector is not a virus, bacterium or other microorganisms—it is an industry and its business strategy.”

In an email exchange, I asked Professor Proctor to expand on this notion of a disease vector:

“We tend to divide "communicable" from "non-communicable" diseases,” Proctor told me, “when the reality is that many "non-communicable" diseases are in fact spread by communications.”

Examples? “Through ignorance and propaganda, for example, which can spread like a virus,” Proctor wrote. “We don't count the anthropogenic communications, oddly enough, even though these can be just as dangerous, and just as deadly. And just as preventable--by changing our exposure environments.”

In a recent article for Tobacco Control, Proctor laid out how the calculus of the disease vector plays out. We know, for example, that smoking will cause roughly 6 million deaths in 2015. And about a third of those will be from lung cancer. We know that 25 acres of tobacco plants will result in about 10 lung cancer deaths per year, starting 20 or 30 years down the road. Here’s a sick equivalence: “A 40 ft container of the sort shipped overseas or trucked by highway houses 10 million cigarettes, which means that each container will cause about 10 deaths.” Proctor works out the numbers for the value of a human life:

“Cigarette companies make about a penny in profit for every cigarette sold, or about $10,000 for every million cigarettes purchased. Since there is one death for every million cigarettes sold (or smoked), a tobacco manufacturer will make about $10,000 for every death caused by their products…. The value of a human life to a cigarette manufacturer is therefore about $10,000.” 

Proctor has even produced a “factories of death” chart, illustrating that arguably the world’s most lethal production plant is Philip Morris’s Richmond cigarette facility, which churned out 146 billion cigarettes in 2010, which adds up to about 146,000 deaths per year.

By 1964, researchers at Harvard had already identified the presence of radioactivity in the form of polonium 210 in cigarette smoke, and the cry went up for safety. As for the notion of safer cigarettes, Proctor says all cigarette filters function the same way—“basically like drinking through a somewhat thinner straw.” He goes even further, arguing that “filters have reduced smoke particle size, producing cancers deeper in the lungs, making them harder to identify and harder to treat.” (Scientists determined that the radiation source was the newer “superphosphate” fertilizers being used heavily on tobacco plants.)

 Next came mandated “tar and nicotine numbers,” which turned out to be misleading measures obtained from smoking robots. Then, “an opportunity presented itself to game the system, as we find in the brilliant trick of ventilation.” Manufacturers pricked tiny holes in the paper near the mouthpiece of cigarettes brands like Carlton and True, which consumers got around by covering the holes with fingers or with “lipping” behavior. “Low tars were a fraud, just as “lights” would be,” Proctor writes. Smokers just smoked harder, or differently, or more frequently. In 1983, pharmacologist Neal Benowitz at UCSF broke the official news in the New England Journal of Medicine: Smokers got just as much nicotine, whether they smoked high-, low-, filtered, unfiltered, regular, light, or ultra-light.  The industry itself had known this for more than 20 years. “Nicotine in the actual rod was rarely allowed to drop below about 10 milligrams per cigarette,” Proctor asserts, “and no cigarette was ever commercially successful with much less than this amount.” (A Philip Morris psychologist compared nicotine-free cigarettes to “sex without orgasm.”)

Indeed, almost every design modification put in place by tobacco companies over the past century, from flue-curing to filters, has served to make cigarettes deadlier than before. “Talk of ‘safer cigarettes’ is rather like talking about safer terrorism, or safer smallpox, or safer forms of drowning,” Proctor concludes.

And the industry testing continues. The point of tobacco-sponsored research is not simply to discredit an individual researcher’s work, but to create an aggregate bias in the pattern of research—a lot of “noise” in the signal. In other words, “you basically fund lots of research to dispute a hazard, then cite this same research to say that lots of scholars dispute it.” We are told about “mucociliary escalators,” which dredge the tar up and out of smokers’ lungs. We learn that “a rabbit will scream if nicotine is introduced into the eye.” We read excerpts from anguished letters to tobacco companies: “Do you suppose if I continue to smoke Camel Ultra Light Cigarettes and I should develop cancer it will be ‘Ultra Light Cancer?’”

Proctor brings us up to date: Harm reduction, he writes, has become the industry’s new mantra. “The companies now want us to believe that less hazardous products can be and are being made and marketed.” Proctor thinks harm reduction “may end up causing even greater harm” if products touted as “safer” make smokers less likely to quit. As for public health campaigns, “consumers are encouraged to stop consuming,” Proctor writes, “but producers are never discouraged from producing.” Or, as Louis Pasteur once wrote: “When meditating over a disease, I never think of finding a remedy for it, but, instead, a means of preventing it.”

So, what comes next? A glimpse of the future may already be here, in the form of cinnamon- and mint-flavored Camel Orbs, “which look like Tic Tac candy and contain about a milligram of nicotine in a highly freebased form.”

As for the industry’s success in corrupting scientists and academics through various means, the story is just as bad as you think it is: “It would take many thousands of pages to chronicle the full extent of Big Tobacco’s penetration of academia; the scale of such collaborations is simply too vast. From 1995 to 2007 alone, University of California researchers received at least 108 awards totaling $37 million from tobacco manufacturers….”

Part II of III.

Photo Credit: http://theloungeisback.wordpress.com/

Judge Rules Against Graphic Cigarette Packs

District Court says FDA mandate would violate First Amendment.

Consumers may yet be spared graphic images of diseased lungs and smokers with holes in their throats, after R.J. Reynolds, Lorillard, and other tobacco companies prevailed over the Food and Drug Administration in the U.S. District Court for the District of Columbia today. Judge Richard Leon ruled that forcing cigarette manufacturers to offer their products only in gruesome packages was a violation of free speech, and therefore unconstitutional. The companies were granted a preliminary injunction, while the FDA regroups and lawyers rehuddle.

The judge wrote that “plaintiffs raise for the first time in our Circuit the question of whether the FDA's new and mandatory graphic images, when combined with certain textual warnings on cigarette packaging, are unconstitutional under the First Amendment. Upon review of the pleadings, the parties' supplemental pleadings, oral argument, the entire record, and the applicable law, the Court concludes that plaintiffs have demonstrated a substantial likelihood that they will prevail on the merits of their position that these mandatory graphic images unconstitutionally compel speech, and that they will suffer irreparable harm absent injunctive relief pending a judicial review of the constitutionality of the FDA's Rule.” (Complete ruling available here).

As Josh Gerstein reported at POLITICO, Leon “found that the new warnings, which occupy 50% of the front and back of cigarette packs, convert them into "mini-billboards...for [the FDA's] obvious anti-smoking agenda." Both Health and Human Services Secretary Kathleen Sebelius and FDA Commissioner Margaret Hamburg were also named in the lawsuit.

Judge Leon foresees a slippery constitutional slope if such mandates are allowed to bloom:

When one considers the logical extension of the Government's defense of its compelled graphic images to possible graphic labels that the Congress and the FDA might wish to someday impose on various food packages (i.e., fast food and snack food items) and alcoholic beverage containers (from beer cans to champagne bottles), it becomes clearer still that the public's interest in preserving its constitutional protections - and, indeed, the Government's concomitant interest in not violating the constitutional rights of its citizens - are best served by granting injunctive relief at this preliminary stage.

Graphics Credit: http://pubcit.typepad.com

Vitamin B6 May Lower Risk of Lung Cancer

Large European study confirms earlier findings.

It doesn’t mean you should start popping handfuls of B vitamins if you are a smoker or a former smoker (those who never smoked rarely get the disease). What it appears to mean is that people with the highest levels of vitamin B6 in their bodies may have as little as half the risk of developing lung cancer as people with very low levels of B6--also known as pyridoxine.

In a June 16 article in the Journal of the American Medical Association (JAMA) , dozens of researchers from around the world deconstructed a European medical database from the 1990s, containing medical data and blood test results for more than 380,000 people. They were looking for meaningful statistical correlations having to do with the 899 people in the study who eventually developed lung cancer.

According to Nathan Seppa in Science News, the international research team found that “people with vitamin B6 levels ranking in the top one-fourth of all the samples taken had less than half the risk of lung cancer as those with the lowest vitamin B6. A similar comparison found that people with high levels of [the amino acid] methionine seemed to have almost half the cancer risk of people with low levels. High folate levels seemed to give less protection.” The researchers calculated that having high levels of all three compounds could reduce lung cancer risk by as much as two-thirds.

Much remains unknown. Can smokers use B6 vitamin supplements to protect against lung cancer, or are the protective effects, if verified, due to a B6 level that reflects diet and other metabolic factors at work over decades? And, as always, there is the question of B6 from vitamin supplements vs. B6 from B6-rich foods like fish, beans, and grains.

A smaller prospective study undertaken in 2001 came up with similar results. Published in the American Journal of Epidemiology, the study involved 300 lung cancer patients in Finland between 1985 and 1993. The researchers looked at B6, B12, and folate, and found “significantly lower risk of lung cancer among men who had higher serum vitamin B6 levels. Compared with men with the lowest vitamin B6 concentration, men in the fifth quintile had about one half of the risk of lung cancer.” The researchers speculate that one of the mechanisms by which B6 could influence carcinogenesis is the role the vitamin plays in homocysteine metabolism. B6 is involved in the complex process of metabolizing homocysteine, another amino acid. Absent sufficient B6, homocysteine levels can build up in the body, causing heart disease and other ailments.

Mattias Johansson, et. al. (2010). Serum B Vitamin Levels and Risk of Lung Cancer Journal of the American Medical Association, 303 (23), 2377-2385

Graphics Credit: http://helios.hampshire.edu/

Cannabis and Cancer

 
Canada considers the case.

The link between cigarette smoking and respiratory disease is irrefutable. But what about pot smoking? A long history of contentious argument and clinical inference has left the picture as fuzzy as ever. Despite strenuous efforts to prove the case, the evidence remains ambiguous.

The Canadian Centre on Substance Abuse in Ottawa recently released an analysis of current evidence, “Clearing the Smoke on Cannabis: Respiratory Effects of Cannabis Smoking.” (PDF). In the report, prepared in 2009 by the Centre for Criminal Justice Research at the University of the Fraser Valley, Jordan Diplock and Darryl Plecas assess the argument that cannabis poses similar risks to the airways as tobacco, primarily due to the tar content of cannabis. It is sometimes argued that cannabis is even more dangerous than tobacco, due to the deeper inhalations and breath-holding manner of smoking typical of pot smokers. The well-known style of high, tight exhalations, while tightening the abdomen, is meant to increase the absorption of THC in the lungs. It is similar to the so-called Valsalva Maneuver, which increases thoracic cavity pressure through forcible exhalation against a closed airway, such as holding one’s nose and attempting to “pop” one’s ears.

Earlier studies by Moore and others had confirmed that “common self-reported respiratory problems include coughing on most days, wheezing, shortness of breath after exercise, nocturnal chest tightness, chest sounds without a cold, early morning phlegm and mucus, and acute and chronic bronchitis. These symptoms were associated to cannabis smoking even when gender, age, tobacco smoking, and asthma were controlled.” Nonetheless, the majority of cannabis smokers in such self-reported results were frequently cigarette smokers as well, making it difficult to assess the health risk such negative respiratory symptoms represent.

A study by Aldington and colleagues in New Zealand in 2008 reported that the risk of lung cancer “increased by 8% for each joint-year of cannabis smoking after adjusting for various confounding variables, including tobacco smoking.”  However, a significant degree of what researchers call “recall bias” may be at work in retrospective studies of this kind. Other studies that found connections have been hospital-based, which can introduce selection bias and other problems.

A 1997 retrospective study of more than 64,000 people in California  found exactly the reverse: “Current and ever-cannabis use (defined as use of cannabis six or more times over a lifetime) was not associated with an increased risk of cancer overall,” after adjusting (or attempting to adjust) for the usual factors like drinking and smoking.  The problem here is that there is no way of knowing whether these studies manage to capture a sufficient number of heavy, long-term marijuana smokers.

Smoking aside, what about the contention that THC in the lungs can damage respiratory tissue? The idea that THC causes immune system deficiencies, which, in turn, hinder the ability of the lungs to fight off pathogens, has been around for some time. But again, the evidence remains inconclusive. In fact, some evidence points in the other direction entirely. By curbing a substance called epidermal growth factor (EGF), THC may in fact confer a protective effect, inhibiting the growth of certain tumors. THC “seems to have a suppressive effect on certain lines of cancer cells,” according to a pulmonary specialist at New York’s Lenox Hill Hospital, quoted in a HealthDay article by reporter Amanda Gardner.

The Canadian authors caution that these inhibitory effects “have been demonstrated using THC (not cannabis smoke) in preclinical models, and do not necessarily imply that exposure to cannabis smoke can prevent cancer occurrence in humans.”

The problem is that, over the past ten years, these conflicting studies suggest either that: a) There is no association between cannabis smoking and an increased risk of chronic obstructive pulmonary disease (COPD), or b) There is a serious risk of COPD in people who smoke both marijuana and tobacco. Unfortunately, there is no c) There is (or is not) evidence of elevated COPD risk among people who smoke pot but not tobacco. And while there is always reason to speculate that sustained pot smoking could put users at risk for pulmonary problems, the authors of the Canadian report concede that the state of the research “is too limited to provide estimates of the prevalence of these and other serious health threats.”

So, the picture remains out of focus. Does pot smoking raise the risk of respiratory diseases, including lung cancer? We still don’t know.  The limited research literature remains wholly inconclusive, and the current connection between lung cancer and cannabis smoking remains weak at best.

Common sense suggests that inhaling hot vegetable matter that has been dried for smoking can’t be a terrific idea on the long run. The Canadian authors make a pitch for vaporizers as a harm-reduction  approach to marijuana smoking. Vaporizers heat the active cannabinoids enough to produce vapors but do not produce enough heat for combustion of the plant material.