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Smoking and Bone
Health
Many of the health consequences of
tobacco use are well established. The Center for Disease
Control reports that smoking-related illnesses result in
nearly $50 billion in direct health care expenses each
year. Cigarette smoking causes heart disease, lung and
esophageal cancer, and chronic lung disease. What is
less clear is the effect of tobacco use on bone density
and fracture risk. While the majority of the research
has implicated smoking as a risk factor for osteoporosis
and fracture, some studies have failed to find an
association.
Tobacco Use and
Bone Density
Cigarette smoking was first identified
as a risk factor for osteoporosis more than 20 years
ago. Subsequent studies have also demonstrated a direct
relationship between tobacco use and decreased bone
density. However, not all studies have supported this
finding. Though the majority of research has focused on
women, studies in men have also identified smoking as a
risk factor for low bone density. In a study by Vogel
and associates on Japanese-American men, bone loss was
greatest at sites with the higher concentrations of
cancellous bone. Significant bone loss has been found in
postmenopausal women and older men with prolonged
smoking exposure. Deficits ranging from .5 to 1.0
standard deviations have been identified in these
groups. In addition, a relationship between cigarette
smoking and low bone density in adolescence and early
adulthood has been identified.
Analyzing the impact of cigarette
smoking on the skeleton can be difficult for several
reasons. It has been suggested that differences in bone
density between smokers and non-smokers may be due to
concomitant lifestyle factors. For example, smokers are
often thinner than their non-smoking counterparts.
Smokers also tend to have a higher consumption of
alcohol, may be less physically active, often have
nutritional deficiencies, and tend to have an earlier
menopause than non-smokers. These characteristics place
many smokers at an increased risk for osteoporosis apart
from their tobacco consumption.
Tobacco Use
and Fracture
While the association between tobacco
use and decreased bone density is fairly strong, the
results are less consistent when fractures are
considered. Most studies suggest at least a slight
association between cigarette smoking and fracture,
especially hip fracture and vertebral fracture. Not all
studies have found such a relationship, however. Studies
have yet to demonstrate an association between tobacco
use and forearm fractures.
Cigarette
Smoking and Estrogen
In an arm of the Framingham study,
Kiel and colleagues found that smoking use did not
increase hip fracture risk in women. Importantly, the
study also concluded that while estrogen replacement
protected women from fracture, this protective effect
was eliminated in women on estrogen replacement who
smoked. Kiel's results support an anti-estrogenic effect
of cigarette smoking that is consistent with the
conclusions of other researchers. For example, smokers
are less likely to develop uterine cancer, fibrocystic
disease and fibroadenoma. Each of these conditions is
believed to be related to estrogenic stimulation. Other
reports have suggested that smokers have less effective
absorption of calcium, opposite to the effect of
estrogen, which is believed to enhance calcium
absorption.
The anti-estrogen effect of tobacco
use may help explain the increased risk for osteoporosis
among female smokers. Postmenopausal smokers have lower
estrogen levels than non-smokers and smokers tend to
have an earlier menopause than their non-smoking
counterparts. This reduction in estrogen is likely to
result in an increase in bone resorption, contributing
to osteoporosis and fracture risk.
On a positive note, researchers have
discovered that smoking cessation, even later in life,
may help limit smoking-related bone loss. |
