Pubdate: Tue, 14 Apr 2009
Source: Vancouver Sun (CN BC)
Copyright: 2009 The Vancouver Sun
Author: Pamela Fayerman


Chances Of Serious Lung Disease About Three Times More Likely Than In 
Non-Smokers, Study Says

People who habitually smoke both tobacco and marijuana are about 
three times more likely than non-smokers to develop serious lung disease.

That affects a lot of people because nearly 20 per cent of 
Vancouverites over the age of 40 do or have done just that, according 
to a new study by a team from St. Paul's Hospital.

People who smoked only cigarettes were 2.7 times more likely than 
non-smokers to have chronic obstructive lung disease. Those who smoke 
or smoked both cigarettes and marijuana were 2.9 times more likely to 
have the disease.

The study, published today in the Canadian Medical Association 
Journal, included nearly 900 Vancouver residents recruited into the 
study by random telephone dialing.

It showed that 14 per cent of participants now smoke only pot and 14 
per cent smoke tobacco. Only 38 of the 856 participants now smoke 
both marijuana and tobacco. But 160 participants (18 per cent) were 
either current or previous users of both.

Consistent with previous population surveys showing B.C. has the 
highest marijuana use in the country, 45.5 per cent of participants 
in the current study said they had used marijuana in the past.

The study was designed to estimate the prevalence of chronic 
obstructive lung disease (COPD) among adults over the age of 40 in 
the general population and the associations with smoking.

Researchers from iCapture Centre for Cardiovascular and Pulmonary 
Research, a department at St. Paul's, had expected 15 per cent would 
have lung disease, but the study found it was 19.3 per cent.

About half of the people with clinical signs of lung disease had not 
yet been diagnosed with it -- they found out when they did lung 
function tests for the purposes of the study.

Lead author and respirologist Dr. Wan C. Tan said those study 
participants were given the results of their tests so they could 
share them with their family doctors, get referred for specialist 
care or, ideally, "take smoking cessation more seriously."

COPD -- which includes chronic emphysema or chronic bronchitis -- is 
often indicated by a continuing cough with phlegm and wheezing or 
shortness of breath. Tan said COPD is a progressive disease and is 
the fourth leading killer in North America, behind cancer, heart 
disease and stroke.

In the study, researchers found that participants with COPD had a 
greater likelihood of other illnesses like asthma, heart disease and 
high blood pressure. They were more likely to have a history of 
hospital admission for respiratory problems.

Marijuana smoking alone did not appear to cause COPD.

Although marijuana-only users had a 1.6 times greater risk of COPD 
than non-smokers, Tan said researchers are not convinced of the 
statistical power of that odds ratio because there were too few study 
participants who used marijuana alone in the COPD group.

Experts have found one marijuana joint is equal to the effects (on 
lungs) of 2.5 to five cigarettes. But while there is well-established 
evidence of lung damage from cigarettes, research has shown 
conflicting results on marijuana use.

The current study does not appear to provide clear answers, except 
for users of either tobacco alone or users of both marijuana and tobacco.

Since the study will now be repeated in other Canadian cities, the 
larger data set should reveal a more convincing picture of 
marijuana's role in the development of lung disease, Tan said.

"Innately, it seems logical that marijuana would be a risk factor for 
COPD. The noxious fumes are identical except for the THC in marijuana 
and the nicotine in tobacco," said Tan, adding there is a synergistic 
effect between marijuana and tobacco smoking. Marijuana may sensitize 
the lungs and exacerbate the effects of tobacco on the airways.

Study authors said the findings should have implications for public 
policy and additional research. "Anti-smoking campaigns should 
include a reduction in marijuana use among their goals, aiming 
especially at those who regularly use both marijuana and tobacco," 
states the paper's conclusion.

The local research was funded through a $200,000 grant from 
pharmaceutical companies AstraZeneca, Boehringer-Ingelheim, 
GlaxoSmithKline and Pfizer Canada. Tan said the companies provided an 
unrestricted grant and had no role in the study design, data 
collection, analysis, interpretation or writing.
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MAP posted-by: Keith Brilhart