Page 114 - JSOM Spring 2018

An Ongoing Series

Epidemiological Evidence and Possible Mechanisms for the
Association Between Cigarette Smoking and Injuries (Part 1)

Joseph J. Knapik, ScD *; Sheryl A. Bedno, MD 2
1

ABSTRACT
Surveys indicated that 24% of military personnel are current Introduction
cigarette smokers. Smoking is well known to increase the risk
of cancers, cardiovascular and respiratory diseases, reproduc- Cigarette smoking and use of other tobacco products are very
tive problems, and other medical maladies, but one of the little common in the United States military. Survey studies indicate
known effects of smoking is that on injuries. There is con- that 24% of military personnel are current cigarette smokers
1
siderable evidence from a variety of sources that (1) smok- and 20% have used smokeless tobacco in the last 12 months.
ing increases overall injury risk, (2) the greater the amount About 32% of Soldiers reported some form of tobacco use
of smoking, the higher is the injury risk, and (3) smoking is with men more than twice as likely to use tobacco products
2
an independent injury risk factor. Smoking not only affects compared with women (35% versus 15%).
the overall injury risk but also impairs healing processes fol-
lowing fractures (e.g., longer healing times, more nonunions, Smoking has numerous well-documented detrimental effects
more complications), ligament injury (e.g., lower subjective on human health. Between 1964 and 2006, there have been
function scores, greater joint laxity, lower subsequent physical 29 US Surgeon General reports on the health consequences
activity, more infections), and wounding (e.g., delayed healing, of smoking. These reports indicate that there is sufficient in-
more complications, less satisfying cosmetic results). Smoking formation to infer a causal relationship between smoking and
may elicit effects on fractures through low bone mineral den- a myriad of cancers (e.g., lung, oral, kidney), cardiovascular
sity (BMD), lower dietary intake of calcium and vitamin D, diseases (e.g., aortic aneurysm, atherosclerosis), respiratory
altered calcium metabolism, and effects on osteogenesis and diseases (e.g., chronic obstructive pulmonary disease, pneu-
sex hormones. Effects on wound healing may be mediated monia), reproductive health problems (e.g., fertility, low birth
through altered neutrophils and monocytes functions resulting rates), and other medical maladies (e.g., cataracts, peptic ul-
3
in reduced ability to fight infections and remove damaged tis- cers). In addition, secondhand smoke (smoke inhaled by those
sue, reduced gene expression of cytokines important for tissue in close proximity to active smokers) increases the risk of lung
4
healing, and altered fibroblast function leading to lower den- cancer, coronary heart disease, and low birthweight.
sity and amount of new tissue formation. Limited data suggest
smoking cessation has favorable effects on various aspects of Whereas many medical problems of smoking are well estab-
bone health over periods of 1 to 30 years. Favorable effects lished, one of the little known or discussed effects of smoking is
on neutrophil and monocyte functions may occur as early as that on injuries. This column will review the literature on the as-
4 weeks, but fibroblast function and collagen metabolism (im- sociation between cigarette smoking, injuries, and healing after
portant for wound remodeling) appear to take considerably injuries with emphasis on data related to military Servicemem-
longer and may be dependent on the amount of prior smok- bers. The possible mechanisms whereby smoking may influence
ing. Part 2 of this series will use this information to explore injuries will then be explored. This is Part 1 of a series, and in
the possibility of a causal relationship between smoking and Part 2 (to be published in the next issue of the Journal of Spe-
injuries. cial Operations Medicine), the possibility that smoking directly
causes injuries (i.e., a causal relationship) will be explored.
There are two older reviews of this topic, but since these were
5,6
Keywords: smoking; injury; cigarettes; tobacco
published, considerable new information has emerged, allowing
a more comprehensive look at the issue and biological plausibil-
ity of the association between smoking and injuries.
*Address correspondence to joseph.j.knapik.ctr@mail.mil
1 MAJ (Ret) Knapik served in the US military as a wheel vehicle mechanic, medic, Medical Service Corps officer, and DoD civilian. He is currently
a senior epidemiologist/research physiologist with the Henry M. Jackson Foundation and an adjunct professor at Uniformed Services University
(Bethesda, MD) and Bond University (Robina, Australia). COL Bedno is the chief, Department of Preventive Medicine at Womack Army Medi-
2
cal Center, Fort Bragg, NC, She is a preventive medicine and occupational medicine physician and researcher.
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