受動喫煙でもニコチン依存症を引き起こす恐れがあるという論文

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2011年05月07日(Sat) 09:12

受動喫煙でもニコチン依存症を引き起こす恐れがあるという論文

Moderate levels of secondhand smoke deliver nicotine to the brain
http://www.nida.nih.gov/newsroom/11/NR5-02.html

   
For Release May 2, 2011

NIH-funded study shows how secondhand smoke may increase vulnerability to nicotine addiction


Exposure to secondhand smoke, such as a person can get by riding in an enclosed car
 while someone else smokes, has a direct, measurable impact on the brain—and the effect
is similar to what happens in the brain of the person doing the smoking. In fact,
exposure to this secondhand smoke evokes cravings among smokers, according to a study
funded by the National Institute on Drug Abuse (NIDA), part of the National Institutes
of Health.

The study, published today in Archives of General Psychiatry, used positron emission
tomography (PET) to demonstrate that one hour of secondhand smoke in an enclosed space
 results in enough nicotine reaching the brain to bind receptors that are normally
targeted by direct exposure to tobacco smoke. This happens in the brain of both smokers
and non-smokers.

Previous research has shown that exposure to secondhand smoke increases the likelihood
 that children will become teenage smokers and makes it more difficult for adult smokers
to quit. Such associations suggest that secondhand smoke acts on the brain to promote
smoking behavior.

"These results show that even limited secondhand smoke exposure delivers enough nicotine
to the brain to alter its function," said NIDA Director Nora D. Volkow, M.D. "Chronic
or severe exposure could result in even higher brain nicotine levels, which may explain
why secondhand smoke exposure increases vulnerability to nicotine addiction."

"This study gives concrete evidence to support policies that ban smoking in public places,
 particularly enclosed spaces and around children,
" said Arthur Brody, M.D., of the UCLA
Department of Psychiatry & Biobehavioral Sciences and corresponding author for the article.

この研究で、公共の場、特に子どもの周りの空間を「完全禁煙」とする施策を支持する、
完全なる証拠が得られた。


The Surgeon General's Report concluded in 2006 that secondhand smoke causes heart disease
and lung cancer in nonsmoking adults and many serious health conditions in children,
including sudden infant death syndrome, respiratory infections, and more severe asthma.
According to the CDC, almost 50,000 deaths per year can be attributed to secondhand smoke.
For more information or for resources to help quit smoking, go to
http://www.nida.nih.gov/DrugPages/Nicotine.html.

The study can be found online at: http://archpsyc.ama-assn.org/.

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Effect of Secondhand Smoke on Occupancy of Nicotinic Acetylcholine Receptors in Brain
http://archpsyc.ama-assn.org/cgi/content/abstract/archgenpsychiatry.2011.51

Arthur L. Brody, MD; Mark A. Mandelkern, MD, PhD; Edythe D. London, PhD; Aliyah Khan, BS;
Daniel Kozman, BS; Matthew R. Costello, BA; Evan E. Vellios, BS; Meena M. Archie, BS;
Rebecca Bascom, MD; Alexey G. Mukhin, MD, PhD

Arch Gen Psychiatry. Published online May 2, 2011. doi:10.1001/archgenpsychiatry.2011.51

Context  Despite progress in tobacco control, secondhand smoke (SHS) exposure remains
prevalent worldwide and is implicated in the initiation and maintenance of cigarette smoking.

Objective  To determine whether moderate SHS exposure results in brain α4β2* nicotinic
 acetylcholine receptor (nAChR) occupancy.


Design, Setting, and Participants  Positron emission tomography scanning and the
radiotracer 2-[18F]fluoro-3-(2(S)azetidinylmethoxy) pyridine (also known as
 2-[18F]fluoro-A-85380, or 2-FA) were used to determine α4β2* nAChR occupancy from
SHS exposure in 24 young adult participants (11 moderately dependent cigarette smokers
 and 13 nonsmokers). Participants underwent two bolus-plus-continuous-infusion 2-FA
positron emission tomography scanning sessions during which they sat in the passenger's
seat of a car for 1 hour and either were exposed to moderate SHS or had no SHS exposure.
 The study took place at an academic positron emission tomography center.

Main Outcome Measure  Changes induced by SHS in 2-FA specific binding volume of
distribution as a measure of α4β2* nAChR occupancy.

Results  An overall multivariate analysis of variance using specific binding volume of
distribution values revealed a significant main effect of condition (SHS vs control)
(F1,22 = 42.5, P < .001) but no between-group (smoker vs nonsmoker) effect. Exposure
to SHS led to a mean 19% occupancy of brain α4β2* nAChRs (1-sample t test, 2-tailed,
P < .001). Smokers had both a mean 23% increase in craving with SHS exposure and
 a correlation between thalamic α4β2* nAChR occupancy and craving alleviation with
 subsequent cigarette smoking (Spearman {rho} = –0.74, P = .01).

Conclusions  Nicotine from SHS exposure results in substantial brain α4β2* nAChR
occupancy in smokers and nonsmokers.
Study findings suggest that such exposure delivers
 a priming dose of nicotine to the brain that contributes to continued cigarette use
in smokers. This study has implications for both biological research into the link
between SHS exposure and cigarette use and public policy regarding the need to limit
SHS exposure in cars and other enclosed spaces.


Author Affiliations: Department of Radiology, Greater Los Angeles Veterans Affairs
Healthcare System (Drs Brody, Mandelkern, and London) and Department of Psychiatry
and Biobehavioral Sciences, University of California, Los Angeles (Drs Brody and London,
 Ms Khan, and Messrs Kozman, Costello, Vellios, and Archie), Los Angeles, and Department
 of Physics, University of California, Irvine (Dr Mandelkern); Department of Pulmonology,
 Pennsylvania State University, Hershey (Dr Bascom); and Department of Psychiatry,
Duke University, Durham, North Carolina (Dr Mukhin).


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