Osteoporosis Screening: What You Need to Know
Worst Pills Best Pills Newsletter article November,
2008
As older adults face pressure from their doctors to be tested (and then possibly treated)
for osteoporosis, it is important that they understand the tools used to determine their diagnosis. The development of new
screening tools for osteoporosis has been helpful in estimating the 10-year risk of a hip or any osteoporotic fracture, but
these tests still omit several important risk factors in their calculation and have the potential for resulting in inappropriate
drug treatment for people who may not necessarily need it.
Osteoporosis is usually diagnosed in one of two ways. First, the patient can have a
low Bone Mineral Density (BMD) score, represented by a so-called “T-score” less than -2.5. BMD is most commonly
measured by dual-emission X-ray absorptiometry (DXA). The T-score represents the number of standard deviations (a representation
of the distribution of BMD values in the population) from the average BMD of a young woman; negative T-scores represent lower
BMDs than average.
The second way osteoporosis may be diagnosed is after a fragility fracture. A fragility
fracture occurs when a bone breaks under a force that would not break a healthy bone, such as falling down from a standing
position.
Did you know?
Osteoporosis is a condition characterized by a decrease in bone mass (quantity) and structure
(quality) leading to fragile bones that are then more susceptible to breaking. Osteoporosis is not so much a disease as it
is a risk factor for fractures; the most serious of which risks is a hip fracture. |
BMD peaks in the 20s and thereafter begins to decline. In women, BMD begins to decline
more rapidly after menopause; this is thought to be due to loss of estrogen production by the ovaries. In order to detect
women at risk for fracture, the U.S. Preventive Services Task Force recommends that all women over 65 years old (and some
women 60-64 years old with risk factors mentioned in B ox 1 ) be screened for low BMD. Screening for low BMD before 65 years of age is controversial
and guidelines are vague. Nonetheless, screening occurs for many women at some point between menopause and 65 years of age.
Screening for low BMD with DXA is intended to identify patients at risk for fractures
so that they might be referred for treatment to prevent fractures. But, much like measuring blood pressure or cholesterol
to screen for stroke or heart disease, BMD is only one aspect of the disorder; microscopic bone architecture and the likelihood
of falling are crucial aspects of fracture risk, yet neither is reflected in a BMD value. While women with a low BMD are at
increased risk for fractures, low BMD (T-score less than -2.5) does not adequately identify most women who will go on to develop
a fracture. Only 25 to 45 percent of women who sustain a fracture have T-scores less
than -2.5. Additionally, in the same patient, the T-score varies depending on
what part of the skeleton is measured.
Because almost 50 percent of fragility fractures occur in patients with T-scores between
-1.0 and -2.5, a condition known as “osteopenia,” the focus is shifting toward recognizing risk factors for fractures
other than low BMD. In consultation with a physician, these factors may be used
to decide whether screening for low BMD is necessary.
New diagnostic tools not requiring BMD: helpful but incomplete
To address the deficiencies in using BMD alone in determining fracture risk, the World
Health Organization recently released an online tool called FRAX (available at http://www.shef.ac.uk/FRAX/ ). FRAX can estimate one’s 10-year risk of hip or any osteoporotic fracture based
on risk factors (such as gender, smoker status and daily alcohol consumption), and can be run with or without the results
from testing for BMD.
A similar tool developed at the University of Washington (available at http://courses.washington.edu/bonephys/FxRiskCalculator.html) uses elements of FRAX combined with several other factors (for instance, do you use
your arms to stand from a chair?) to provide a more detailed and technical assessment of fracture risk, but, unlike the WHO
calculator, this tool requires knowledge of one’s T-score.
However, despite the usefulness of these tools, several important aspects of fracture
risk are left out. For instance, exercise substantially increases BMD and reduces
the likelihood of falling; yet physical activity is not accounted for in either online assessment. Falling is the antecedent
to most hip fractures; however, several important determinants of one’s risk of falling were not included in FRAX.
Below, we illustrate how these tools can be used and how, surprisingly often,
a BMD measurement alone would not lead to a change in treatment. The examples use the FRAX tool and are based on the assumption
that only those with a risk of a hip fracture of 3 percent or greater in the next 10 years should begin treatment
with medication.
Low-risk patient. Using FRAX without any BMD data, a 55-yearold
white female who is five feet four inches tall and weighs 169 pounds with no risk factors has only a 0.4 percent chance of
fracturing her hip in the next 10 years (before she is 65 years old). This less than 1 percent risk is obviously much less
than the 3 percent risk of hip fracture that might indicate the need for medication. The same lower-than-3 percent risk would
also be true for women 60 or 70 years old of the same height and weight with no risk factors.
Using FRAX with BMD information, even if the 55-year-old woman had a T-score equal
to -2.5 (osteoporosis), her 10-year hip fracture risk is still only 2.6 percent. Thus, with or without the BMD results, this
patient would not be a candidate for treatment.
Intermediate-risk patient. If the 55-year-old woman in the first
case was a smoker and had a previous fragility fracture, without knowing her T-score, her risk of hip fracture before 65 years
is 2.2 percent. However, with a T-score of -2.5, her hip fracture risk would rise dramatically to about 9 percent. For this
patient, assessing BMD could lead to her being treated.
High-risk patient. If, in addition to smoking and a previous
fracture, the patient drinks three alcoholic beverages per day and is on steroids for rheumatoid arthritis, even without a
BMD, her 10-year fracture risk is 12 percent, high enough to merit treatment. Screening for low BMD would not alter her treatment.
In sum, while measuring BMD can be a useful diagnostic test, all too often, its deficiencies
are overlooked. Consequently, far more women receive the test than are likely to benefit from it and may well be started on
drug treatment based only on the results. No doubt one of the reasons for the heavy emphasis on BMD is the large industry
it supports: the companies who make the equipment and the doctors who profit from doing the tests. Most of the other risk
factors can be determined in the course of a routine doctor visit, but screening for low BMD requires a diagnostic test that
can be reimbursed. We can achieve better application of our limited resources with a more thoughtful approach that stratifies
patients according to the many risk factors that contribute to fracture, rather than relying so heavily on primarily screening
for low BMD.
Box 1.
Risk factors for fractures
• Age • Previous fragility fracture • Any condition that increases
a person’s risk of falling • Relatives with fractures • Smoking • Excessive alcohol use •
Immobility • Steroid use • Thinness • Caucasian/Asian ancestry • Elevated levels of thyroid
hormones • Rheumatoid arthritis • Early menopause |
A way to compare what Worse Pill published
with that of another reliable source, Wikipedia;
FROM WIKIPEDIA:
Screening
The U.S. Preventive Services Task Force (USPSTF) recommended in 2002 that all women 65 years of age or older should be screened with bone densitometry.[27] The Task Force recommends screening only those women ages 60 to 64 years of age who are at increased risk. The best
risk factor for indicating increased risk is lower body weight (weight < 70 kg), with smoking or family history. There
was insufficient evidence to make recommendations about the optimal intervals for repeated screening and the appropriate age
to stop screening. Clinical prediction rules are available to guide selection of women ages 60-64 for screening. The Osteoporosis Risk Assessment
Instrument (ORAI) may be the most sensitive strategy[28]
Regarding the screening of men, a cost-analysis study suggests that screening may be "cost-effective
for men with a self-reported prior fracture beginning at age 65 years and for men 80 years and older with no prior fracture".[29] Also cost-effective is the screening of adult men from
middle age on to detect any significant decrease in testosterone levels, say, below 300.
Medication
Certain medications have been associated with an increase in osteoporosis risk; only steroids
and anticonvulsants are classically associated, but evidence is emerging with regard to other drugs.
Potentially modifiable
- Excess alcohol - small amounts of alcohol do not increase osteoporosis risk and may even be beneficial,
but chronic heavy drinking (alcohol intake greater than 2 units/day),[7] especially at a younger age, increases risk significantly.[8]
- Vitamin D deficiency[9] - low circulating Vitamin D is common among the elderly worldwide.[10] Mild vitamin D insufficiency is associated with increased Parathyroid Hormone (PTH) production. [10] PTH increases bone reabsorption, leading to bone loss. A positive association exists between serum 1,25-dihydroxycholecalciferol levels and bone mineral density, while PTH is negatively associated with bone mineral
density.[10]
- Tobacco smoking - tobacco smoking inhibits the activity of osteoblasts, and is an independent risk
factor for osteoporosis.[7][11] Smoking also results in increased breakdown of exogenous estrogen, lower body weight and earlier menopause, all of
which contribute to lower bone mineral density.[10]
- High body mass index - being overweight protects against osteoporosis, either by increasing load or through
the hormone leptin.[12]
- Malnutrition - low dietary calcium intake, low dietary intake of vitamins K and C[9] Also low protein intake is associated with lower peak bone mass during adolescence and lower bone mineral density in
elderly populations.[10]
- Physical inactivity - bone remodeling occurs in response to physical stress. Weight bearing exercise can increase peak bone mass achieved in adolescence.[10] In adults, physical activity helps maintain bone mass,
and can increase it by 1 or 2%.[citation needed] Conversely, physical inactivity can lead to significant bone loss.[10]
- Excess physical activity - excessive exercise can lead
to constant damages to the bones which can cause exhaustion of the structures as described above. There are numerous examples of marathon runners who developed severe osteoporosis later in life. {I have always
recommended running no more than 2 miles—jk} In women, heavy exercise can lead to decreased estrogen levels, which predisposes to osteoporosis. Intensive training is often associated
with low body mass index.[citation needed]
- Heavy metals - a strong association between cadmium, lead and bone disease has been established. Low level exposure to cadmium is associated
with an increased loss of bone mineral density readily in both genders, leading to pain and increased risk of fractures, especially
in the elderly and in females. Higher cadmium exposure results in osteomalacia (softening of the bone).[13]
- Soft drinks - some studies indicate that soft drinks (many of which contain phosphoric acid) may increase risk of osteoporosis;[14] Others suggest soft drinks may displace calcium-containing drinks from the diet rather than directly causing osteoporosis.[15]
Pathogenesis
The underlying mechanism in all cases of
osteoporosis is an imbalance between bone resorption and bone formation. In normal bone, there is constant matrix remodeling of bone; up to 10% of all bone mass may be undergoing remodeling at any point
in time. The process takes place in bone multicellular units (BMUs) as first described by Frost in 1963.[30] Bone is resorbed by osteoclast cells (which derive from the bone marrow), after which new bone is deposited by osteoblast cells. [5]
The three main mechanisms by which osteoporosis
develops are an inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive
bone resorption and inadequate formation of new bone during remodeling. An interplay of these three mechanisms underlies the
development of fragile bone tissue.[5] Hormonal factors strongly determine the rate of bone
resorption; lack of estrogen (e.g. as a result of menopause) increases bone resorption as well as decreasing the deposition of new bone that normally
takes place in weight-bearing bones. The amount of estrogen needed to suppress this process is lower than that
normally needed to stimulate the uterus and breast gland. The α-form of the estrogen receptor appears to be the most important in regulating bone turnover.[5] In addition to estrogen, calcium metabolism plays a significant role in bone turnover, and deficiency of calcium and vitamin D leads to impaired bone deposition; in addition, the parathyroid glands react to low calcium levels by secreting parathyroid hormone (parathormone, PTH), which increases bone resorption to ensure sufficient calcium in
the blood. The role of calcitonin, a hormone generated by the thyroid that increases bone deposition, is less clear and probably not as significant as
that of PTH.[5]
In hypogonadal men testosterone has been shown to give improvement in bone quantity and quality, but, as of 2008,
there are no studies of the effects on fractures or in men with a normal testosterone level.[18]
Selective estrogen receptor modulator (SERM)
SERMs are a class of medications that act on the estrogen receptors throughout the body in a
selective manner. Normally, bone mineral density (BMD) is tightly regulated by a balance between osteoblast and osteoclast activity in the trabecular bone. Estrogen has a major role in regulation of the bone formation-resorption
equilibrium, as it stimulates osteoblast activity. Some SERMs such as raloxifene (Evista), act on the bone by slowing bone resorption by the osteoclasts.[38] SERMs have been proved as effective in clinical trials.[39][40]
The role of calcium in preventing and treating
osteoporosis is unclear - some populations with extremely low calcium intake also have extremely low rates of bone fracture,
and others with high rates of calcium intake through milk and milk products have higher rates of bone fracture. Other factors, such as protein,
salt and vitamin D intake, exercise and exposure to sunlight, can all influence bone mineralization, making calcium intake
one factor among many in the development of osteoporosis.[42] In the report of WHO(World Health Organization) in 2007, because calcium is consumed by an acid load with
food, it influences osteoporosis.[43][44]. A meta-analysis of randomized controlled trials involving calcium and calcium plus vitamin D supported the use of high levels of calcium
(1,200 mg or more) and vitamin D (800 IU or more), though outcomes varied depending on which measure was used to assess bone
health (rates of fracture versus rates of bone loss).[45] The meta-analysis, along with another study, also supported much better outcomes for patients with high compliance to the treatment protocol.[46]
Vitamin D
Some studies have shown that a high intake of vitamin D reduces fractures in the elderly,[45][48] though the Women's Health Initiative found that though calcium plus vitamin D did increase bone density, it did not affect hip fracture
but did increase formation of kidney stones.[49]
[edit] Exercise
Multiple studies have
shown that aerobics, weight bearing, and resistance exercises can all maintain or increase BMD in postmenopausal women.[50] Many researchers have attempted to pinpoint which types of exercise are most effective at improving BMD and other metrics
of bone quality, however results have varied. One year of
regular jumping exercises appears to increase the BMD and moment of inertia of the proximal tibia[51] in normal postmenopausal women. Treadmill walking, gymnastic training, stepping, jumping,
endurance, and strength exercises all resulted in significant increases of L2-L4 BMD in osteopenic postmenopausal women.[52][53][54] Strength training elicited improvements specifically in distal radius and hip BMD.[55] Exercise combined with other pharmacological
treatments such as hormone replacement therapy (HRT) has been shown to increases BMD more than HRT alone.[56]
Additional benefits for osteoporotic patients other than BMD increase include improvements
in balance, gait, and a reduction in risk of falls.[57]
Epidemiology
It is estimated[citation needed] that 1 in 3 women and 1 in 12 men over the age of 50 worldwide have osteoporosis. It is responsible for millions
of fractures annually, mostly involving the lumbar vertebrae, hip, and wrist. Fragility fractures of ribs are also common in men. It is estimated that a 50-year-old white woman has a 17.5% lifetime risk of fracture of the proximal femur. The incidence of hip fractures increases each decade from the sixth through the
ninth for both women and men for all populations. The highest incidence is found among those men and women ages 80 or older.[62]
In the United
States, 250,000 wrist fractures annually are attributable to Osteoporosis.[61] Wrist fractures are the third most common type of osteoporotic fractures. The lifetime risk of sustaining a Colles'
fracture is about 16% for white women. By the time women reach age 70, about 20% have had at least one wrist fracture.[62]
Exercise
Achieving a higher peak bone mass through exercise and proper nutrition during adolescence
is important for the prevention of osteoporosis. Exercise and nutrition throughout the rest of the life delays bone degeneration.
Jogging, walking, or stair climbing at 70-90% of maximum effort three times per week, along with 1,500 mg of calcium per day,
increased bone density of the lumbar (lower) spine by 5% over 9 months. Individuals already diagnosed with osteopenia or osteoporosis
should discuss their exercise program with their physician to avoid fractures.[64]
|