Osteoporosis
With more and more people living longer,
specific health concerns important to the aged
have surfaced. One of these health concerns is
osteoporosis, a systemic disease of the skeleton,
characterized by low bone mass and bone loss,
which can lead to skeletal vulnerability. Travel
to the National Osteoporosis Foundation to view
fast facts on osteoporosis (R). The National Osteoporosis
Foundation reported in 1997 that osteoporosis is
too often misunderstood. Apparently, many wait
for the appearance of symptoms seen in
arthritis--swollen joints and pain--before
worrying about the disease. Unfortunately,
osteoporosis arrives without warning signals and
may subsequently remain undetected until an
affected individual suffers a fracture, usually
in the hip, spine or wrist. Such fractures can
impair an individual's posture and mobility, as
well as cause significant pain and deformity. The National
Institute of Arthritis and Musculoskeletal and Skin Diseases
provides information on differentiating among osteoporosis,
osteoarthritis and rheumatoid arthritis (O).
Bone is a very metabolically active tissue.
That is, new cells form and old cells degenerate
continuously. When the rate of old bone breakdown
("resorption") exceeds the rate of new
bone formation, osteoporosis may result. Susan
Ott, Associate Professor within the Department of
Medicine at the University of Washington,
maintains a website about bone physiology. The site
includes information, photos and animations about
bone, including a page explaining and
demonstrating the growth and breakdown process (O). Travel to the
National Osteoporosis Foundation to see images
of normal and osteoporotic bone (R) and to read a
more thorough description of bone
basics (O). In the mid 1990's the World
Health Organization categorized bone density
across several stages: normal, low bone mass
(also known as osteopenia),
osteoporosis (low bone density without occurring
fractures), and established osteoporosis (low
bone density resulting in fractures). For the
statistician, "normal" bone mass is
considered to be within one standard deviation of
average, "osteopenia" to be between
1-2.5 standard deviations below average,
"osteoporosis" to be 2.5 or greater
standard deviations below average. The Surgeon General's Report
on
Bone Health and Osteoporosis references a bone mineral
density assessment associated with the National Health and
Nutrition Examination Survey. Based on data obtained in the
assessment, future estimates
of low bone mass and osteoporosis were derived (O).
The human skeleton is made of two types of
bone, cortical and trabecular bone.
Cortical bone is found predominantly in the
peripheral skeleton, which includes bones in the
pelvis, shoulders, and limbs. Trabecular bone,
conversely, is predominantly found in the axial
skeleton, including bones within the skull, ribs,
sternum and spine. Trabecular bone has a higher
"turnover" rate than does cortical
bone, meaning more new trabecular is formed per
year than cortical bone. Consequently, trabecular
bone--particularly in the spinal region-is more
prone to osteoporosis than cortical bone. The hip joint contains
varying amounts of cortical and trabecular bone. While the
femoral neck is typically higher in cortical bone, the
"Ward's Triangle" area of the hip is mostly
trabecular. To see an illustration of varying trabecular and
cortical bone across a few skeletal sites, visit Merckmedicus.com
(O). Susan Ott's Osteoporosis and Bone Physiology course website
shows illustrations of cortical
and trabecular bone differences (R-scroll to the bottom of
the page). University of Utah's Webpath
has a photo of fractured vertebral bone (R).
Risk Factors
There are many risk factors associated with
an increased risk for osteoporosis. Some of these
risks include:
Sex
Women are more at risk for osteoporosis than
are men. The reasons for this are multifactorial
and relate to other risk factors, particularly a
woman's loss of the hormone estrogen during
menopause. In advanced age, however, men begin to
experience osteoporosis-related incidents more
frequently, which means men are at risk as well.
According to the National
Osteoporosis Foundation, two million men
currently have osteoporosis while an additional
12 million are at risk for the disease (O). Since the National
Osteoporosis Foundation estimates 10 million Americans have the
disease, that means eight million women have osteoporosis.
Estrogen Deficiency
Estrogen deficiency has been shown to have an
impact on osteoporosis risk. Estrogen deficiency
can occur naturally in women as a result of
menopause; it can also occur earlier in life if a
female's ovaries are removed or if a female
experiences prolonged amenorrhea (the stopping of
menstruation). Amenorrhea is frequently seen in
women with eating disorders, particularly
anorexia nervosa, and in athletes who have a very
low body fat percentage, such as cross country
runners, gymnasts, and dancers.
Diet
Currently, Americans do not consume enough
calcium, a mineral important in bone formation. Individuals who
do not consume adequate levels of calcium, then are at risk
for developing poor bone health. Like calcium, Vitamin D is also important in maintaining bone
mineral content. Consuming megadosage of Vitamin D,
however, can be toxic to the body. Excessive
protein intake may also be a factor in
osteoporosis risk, due to an increased risk of mineral loss
(through urine) with protein overconsumption. Alcohol
consumption can also play a role in bone health. Travel to the
National Institute of Arthritis and Musculoskeletal and Skin
Diseases to read about the
alcohol-osteoporosis
link (R--scroll down the page to read
"The Link Between Alcohol
and Osteoporosis"). Overconsumption of
Vitamin A may interfere with Vitamin D in bone preservation,
or even increase the rate of bone loss. The NIAMS provides
information on Vitamin
A and bone health (O).
Ethnicity/Race
Caucasians and Asians have greater risk for
osteoporosis than do African Americans. Asian
women, for example, tend to be slender, which
seems to increase the risk for the disease (see
"Body Size," below). African American
individuals have a higher bone density than do
Caucasian and Asian individuals, although this
group also needs to be aware of other
osteoporosis risk factors. As the Latino
population in America continues to grow,
osteoporosis also becomes a more important
concern for this group. Travel to National
Institutes' of Health Osteoporosis and Related
Bone Diseases--National Resource Center to learn
more about osteoporosis among Hispanic
women, Asian
American women and African-American
women (O). The Chicago Sun-Times provides
information via AOL about African-Americans and osteoporosis
in a
video interview with Dr. Monica Luchi
(O).
Body Size
Individuals with smaller frames tend to be at
increased risk for osteoporosis. That is,
individuals who have smaller
bones are more at risk for osteoporosis, as they tend to have
less bone mass to lose with age. A small-framed person who does
not weigh very much is at further risk for osteoporosis due to a
lessened about of weight bearing on the bones, when
compared to a larger person.
Age
Humans continue to accumulate bone mass until
approximately the age of 35, when bone loss begins to slowly
outpace bone growth. This is currently an
inevitable process associated with aging.
Although osteoporosis among children and
adolescents is rare, it does happen. Juvenile
osteoporosis (O, from the NIH Osteoporosis
and Related Bone Diseases--National Resource
Center) can result from an underlying medical or
genetic disorder.
Other risk factors associated with the disease
include smoking, family history, certain medications, smoking,
excessive alcohol consumption, and medical
history.
Educational
Enrichment
Visit the National Osteoporosis Foundation to
find information on medications
and osteoporosis
Osteoporosis is often assessed through dual
energy x-ray absorptiometry (DEXA). View an
example of a
DEXA
scan Diagnostic Imaging Pathways.
The National Library of Medicine has an
interactive tutorial
on osteoporosis, viewable through Adobe Acrobat
Reader or through Flash
Osteoporosis Prevention and
Treatment
Although some of the risk factors associated
with osteoporosis are unalterable, there are
lifestyle choices and medical treatments which
can minimize the severity of the disease. These
include exercise, diet, and pharmacotherapy.
Exercise
Physical activity appears to minimize
osteoporotic bone loss. More specifically,
activities involving impact seem to have more
affect on preventing bone loss than do non-impact
activities. Examples of impact activities include
walking and running. Impact occurring through a
sport such as tennis, where a hand-held racquet
strikes a ball, also appear to increase bone
mass. Research in the late 1970's and early
1980's compared tennis players' hitting arms with
non-hitting arms and found a greater amount of
bone in the hitting arms. Furthermore, in
comparing the tennis players' hitting arms with
dominant arms among non-athletes, researchers
found greater bone mineral content among the
athletes. Weight training, due to the resistance
placed against the bones when performing the
activity, can also be used to optimize bone
mineral content.
The effect of gravity can also be related to
bone mineral maintenance. Many animal studies
show that when limbs are lifted in the air for
long periods of time ("unweighting"),
that bone loss occurs. This idea can be
illustrated by the great care taken during and
after an astronaut's flight. The earth's
gravitational pull is lost during the trip, and
the astronaut subsequently loses bone mass. an
astronaut will typically incorporate an hour or
two of exercise into the daily regimen to combat
the bone loss. PBS has a photo of astronaut Rick
Sturckow on his
cycle
ergometer (O). Travel to the NASA Space Life
Sciences Outreach for more information related to
"the
role of exercise in space" (O).
Diet
A diet with appropriate amounts of calcium and
Vitamin D is important in minimizing one's risk
for osteoporosis, although neither supplement can
replace estrogen when considering disease risk.
Regarding calcium supplementation and subsequent
absorption, researchers seem to favor calcium
citrate over calcium carbonate. Anyone
considering calcium supplementation should
consult his/her physician before purchasing a
product. The National
Osteoporosis Foundation describes the
importance of and lists food and beverage sources
for calcium and
Vitamin D (O). Overconsumption of
alcohol can also increase risk for osteoporosis.
Alcohol affects hormonal levels and calcium
balance, and can of course increase risk for
falling.
Pharmacotherapy
Estrogen replacement therapy (ERT) has been
used in postmenopausal women to prevent the early
onset of osteoporosis. There are, however,
serious side effects associated with ERT, so
women should discuss this therapy with their
physicians before deciding to pursue this
treatment. Interestingly, when ERT first emerged
as a treatment for osteoporosis, many researchers
and clinicians urged its use because of the
reported cardiovascular benefits associated with
it. A 1998 article published in Doctor's
Guide, for example, cites the protective
benefits of ERT (O). Currently, however, many
professionals feel ERT may not only fail to
provide protective cardiovascular benefits but actually worsen a person's
cardiovascular risk. ERT has also been shown to
increase cancer risk among many, particularly
those with a family history of the disease. At least one
component of the famous Women's Health Initiative research
project was halted because of a significantly increased breast
cancer risk among those who participated in the project.
The National Osteoporosis Foundation
recognizes there is no cure for the disease, but
does provide information on medications used to prevent
and treat the condition (O). One of the
first non-hormonal medications manufactured to treat
osteoporosis was Fosamax.
With generic equivalents (alendronate is the main active
ingredient) now available, prescriptions for Fosamax have
reduced. Interestingly, as of early 2010 the makers of
Fosamax, Merck, are facing
mounting legal troubles. According to a 2009
New York Times article, there are over 900 cases
involving plaintiffs who claim Fosamax has caused a rare jaw
condition (O). Merck has experienced some success as well as
disappointment in fighting three bellwether cases. While
Merck was awarded judgement in one case, another led to
mistrial, and a third is scheduled for trial in
April 2010 (O--Druginjury.com).
Boniva
(generic name ibandronate, can be taken as pill or injection)
and
Evista
(generic name raloxifene) are among the
newer drugs
approved by the FDA for osteoporosis prevention
(O). Other therapeutic drugs which have been
approved or are currently under investigation
include calcitonin, parathyroid hormone, other bisphosphanates,
and sodium fluoride.
Educational
Enrichment
U.S.
Department of Health & Human Services: Bone Health and
Osteoporosis, a Report of the Surgeon General
Calcium
Supplements: What to Look For (NIAMS)
Calcium
and Vitamin D: Important at Every Age (NIAMS)
CenterWatch Clinical Trials Listing Service is
a site which provides information on currently
performed clinical research as well as new drug
therapies. Travel to this site for specific
information regarding
osteoporosis
and
clinical
trials in hormone replacement therapy.
Studies
of Drugs and Other Measures to Prevent and Treat
Osteoporosis; A Guide for Non-Experts (World
Health Organization, John D. Wark--Adobe Acrobat
needed to read)
Women's
Health and Aging Study
The North
American Menopause Society
Susan Ott, MD, authors an "Osteoporosis
and Bone Physiology" continuing medical
education offering
The Mayo Clinic has information on staying
active safely
National Osteoporosis Foundation provides
information on reading
bone density test results
The Nun
Study at the University of Kentucky is a
longitudinal study funded to examine aging and another condition
associated with aging, Alzheimer's Disease
Last Revised: 3-9-10
