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Sunday, 10 February 2013

Cannabis smokers show greater lung capacity and lower cancer levels than non-smokers


Cannabis smokers show greater lung capacity and lower cancer levels than non-smokers

by Raw Michelle

cannabisFor many years, the demonizing claims being made against cannabis have been crumbling as research slowly dispels them. Fifty years ago people earnestly believed that the consumption of cannabis was directly linked to the development of an array of mental illnesses, and violent and hypersexual behavior.
 

Medical opinion must be guided by research

 

But these prejudices are still hanging on. Today, an individual who responsibly informs their doctor of their marijuana use, because, as with any medicine, chemical interactions may change the resulting chemical behavior, are most frequently urged to cut back. Various reasons are given for a physicians concern. Some, who appear to have fallen behind on the research, still express concern about "brain cell damage" a remnant from the Reagan era's Just Say No campaign.

The main objection, that even the most well-informed physicians feel justified in making, is that even if cannabis itself is not particularly harmful, its most common method of ingestion, smoking, is bad for the lung tissue, regardless of the harmlessness of the substance being smoked. The belief piggybacked its way in on the back of growing opposition to tobacco, and the understanding that tobacco obstructs pulmonary flow and shortens breath.

 

When a chemical defined by its action doesn't act

 

 

Because some of the same chemicals, which have identifiable carcinogenic impact in cigarettes, are also found in cannabis smoke, many believe that the cancer-causing potential of cannabis is proportionate to the amount of these chemicals. The fact that cannabis contains four times more tar (or oil) than cigarettes sparked the 1990s claim that smoking a joint was as bad for the lungs as smoking four cigarettes. This extrapolation makes perfect sense at face value, but doesn't hold up when compared to actual cancer rates.

 

Rewriting the medical records

 

 

The results of a new government-run research program are now forcing medical authorities to overturn these beliefs. The study has been ongoing for the past twenty years, following the smoking habits of over 5000 people. Researchers found that, contrary to popular belief, smoking cannabis, does not interfere with lung function or capacity. This holds true for ongoing regular -even including daily- and long term consumption. Curiously, as a general rule, cannabis smokers had better lung function than nonsmokers, which researchers attribute to the smoking action itself, rather than the cannabis. Pot smokers inhale deeply and hold those breaths to make the most of their supply, expanding the lung's capacity.

Dr. Tashkin found that, in almost all instances, cannabis consumers had rates of cancer that were no different from those who didn't smoke cannabis. The one exception to this rule was between cannabis smokers and individuals who didn't smoke anything (including tobacco), in which marijuana smokers actually had lower levels of lung cancer.



From Natural News @ http://www.naturalnews.com/035980_cannabis_smokers_cancer.html


Association Between Marijuana Exposure and Pulmonary Function Over 20 Years

Mark J. Pletcher, MD, MPH; Eric Vittinghoff, PhD; Ravi Kalhan, MD, MS; Joshua Richman, MD, PhD; Monika Safford, MD; Stephen Sidney, MD, MPH; Feng Lin, MS; Stefan Kertesz, MD


…The 5115 CARDIA participants recruited in 1985-1986 contributed 20 777 total visits that included pulmonary function testing. Of these, 959 visits were excluded for lack of complete information on smoking behavior, 114 for lack of height or waist measurements, and 1 for an unknown visit date, leaving 19 703 visits (95%) with complete data from 5016 participants (98%). Participants contributed 3.9 visits/participant on average; attrition was more common in tobacco smokers but not associated with marijuana use. FEV1 and FVC varied across participants, increased slightly with age through the late 20s, and declined slowly thereafter (Figure 1).

 
Figure 1. Pulmonary Function Measurements by Age
 
Participants (n = 5017) contributed an average of 3.9 measurements per person (n = 19 705 total) over the course of 20 years. A lowess smoother was used to calculate the smoothed average. FEV1 indicates forced expiratory volume in first second of expiration; FVC, forced vital capacity.

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More than half of participants (54%; mean age at baseline, 25 years) reported current marijuana smoking, tobacco smoking, or both at 1 or more examinations (Table 1). Smoking patterns differed by race and sex, with black women most likely to smoke tobacco only, white men most likely to smoke marijuana only, and black men most likely to smoke both. Tobacco smokers tended to have lower education and income and to be slightly shorter and less active, whereas marijuana smokers tended to be taller and more active. The median intensity of tobacco use in tobacco smokers was substantially higher (8-9 cigarettes/d) than the median intensity of marijuana use in marijuana smokers (2-3 episodes in the last 30 days). Although marijuana and tobacco exposures were strongly correlated, our sample included 91 participants with no tobacco exposure and more than 10 joint-years of marijuana exposure (contributing 153 observations of pulmonary function), 40 (56 observations) of whom had more than 20 joint-years of exposure.

Table 1. Characteristics of CARDIA Participants With Pulmonary Function Test Results, by Smoking Behavior

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In fully adjusted models that considered 4-level categorizations of current and lifetime exposure to tobacco and marijuana, tobacco smoking (both current and lifetime) was associated with a lower FEV1 and current smoking with a lower FVC (Table 2). For example, compared with zero exposure, FEV1 was 63 mL lower (95% CI, 89 to 36; P < .001 for trend) and FVC was 69 mL lower (95% CI, 97 to 41; P < .001 for trend) with current tobacco exposure of more than 20 cigarettes per day and 101 mL lower (95% CI, 136 to 65; P < .001 for trend) with lifetime tobacco exposure of more than 20 pack-years.


Table 2. Associations Between Categorized Exposure to Tobacco and Marijuana Smoke and Pulmonary Function

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In contrast, exposure to marijuana (both current and lifetime) was associated with higher FVC and lifetime exposure with higher FEV1. For example, compared with zero exposure, FVC increased with greater lifetime exposure in joint-years (P = .01 for trend) and FEV1 increased with greater lifetime exposure of up to 10 joint-years and then declined to 36 mL (95% CI, 6.5 to 79) greater than the zero exposure level (P = .049 for trend). FVC increased with smoking intensity up to 20 marijuana smoking episodes in the past 30 days and then declined to 20 mL greater than the zero exposure level (P = .03 for trend). We found no statistically significant interactions between tobacco and marijuana exposure for either FEV1 or FVC.

When we modeled current and lifetime tobacco and marijuana exposure as continuous exposures and permitted flexible nonlinear associations (via splines), we again found strong, dose-related associations (P < .001) between increasing exposure to tobacco and lower FEV1 and FVC (Figure 2), with no evidence of nonlinearity (Table 3). Declining slopes ranged as steep as 2.8 mL (95% CI, 4.8 to 0.7; P = .007) per additional cigarette smoked per day and 7.0 mL (95% CI, 10 to 3.7; P < .001) per additional pack-year for FEV1 and were of similar magnitude for FVC (Table 3). At 50 pack-years of exposure, FEV1 was on average 332 mL lower (95% CI, 401 to 263; P < .001) and FVC was 229 mL lower (95% CI, 310 to 147; P < .001), compared with no exposure.

 
Figure 2. Associations Between Continuous Smoothed Exposure to Current and Lifetime Tobacco and Marijuana and Pulmonary Function
 

Associations between continuous current and lifetime exposure measurements and pulmonary function were modeled via cubic splines (see “Methods”). All 4 exposure measurements were included in each model (one model each for forced expiratory volume in the first second of expiration [FEV1] and forced vital capacity [FVC]). Mixed models with a random intercept and a random 3-knot age spline were used to adjust for repeated measures, and fixed effects were included for year, center and center-year (their interaction), race-sex category, education, and asthma; cubic splines for age, height, waist circumference, secondhand smoke exposure, and exposure to airborne particulate matter less than 10 microns and less than 2.5 microns in size; and interactions between the age spline variables and race-sex, asthma, waist spline variables, and height spline variables. Point estimates and confidence intervals for slopes and net associations at different exposure levels are provided in Table 3.

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Table 3. Estimated Slopes and Net Associations Between Continuous Smoothed Exposure to Current and Lifetime Tobacco and Marijuana and Pulmonary Function

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For marijuana, we found strong statistical evidence that associations between marijuana use and pulmonary function were nonlinear (Figure 2, Table 3). At low lifetime exposure levels, increasing marijuana use was associated with a steep increase in both FEV1 (13 mL/joint-year higher [95% CI, 6.4 to 20], P < .001) and FVC (20 mL/joint-year higher [95% CI, 12 to 27], P < .001), but at higher levels of exposure (>7 joint-years), the slope leveled or even turned downward. At more than 10 joint-years of lifetime exposure, we found a nonsignificant decline in FEV1 (2.2 mL/joint-year [95% CI, 4.8 to 0.3], P = .08) but a significant decline in FEV1 at more than 20 episodes of marijuana use per month (3.2 mL/episode [95% CI, 5.8 to 0.6], P = .02). Although net associations with FEV1 became negative at very high exposure levels (>40 joint-years or >25 episodes/mo), these negative deflections were not statistically significant (Table 3). FVC remained significantly elevated in even heavy users (eg, 76 mL [95% CI, 34 to 117; P < .001] at 20 joint-years).



From the Journal of the American Medical Association @ http://jama.jamanetwork.com/article.aspx?articleid=1104848#qundefined


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4 comments:

  1. It goes without saying that smoking is a dangerous habit.
    In spite of knowing the truth. Smoking causes many fatal diseases.
    It causes cancer, heart attack, chronic bronchitis and some other diseases.


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