Overview
Osteoporosis is a common condition resulting in brittle bones which break more easily, sometimes with very little force. It is a disease which usually affects the whole skeleton. In this condition, the amount of bone is decreased, and thinning of the bone structure occurs (Fig 1), leading to fragile bones.
  Osteoporosis usually occurs in older women (over 55 years old), but younger women and men may also be affected. Because the population of Singapore is aging rapidly, osteoporosis is likely to become an increasingly important health problem.
Osteoporosis is a problem because it may lead to fractures.
Osteoporosis is usually silent until the first fracture occurs. The common sites of fracture are at the wrist, spine and hip (Fig 2). Fractures cause pain and disability, and may lead to deformity.
 Spine Fractures
Unexplained backpain in both men and women is common. In most cases, it is not due to osteoporosis as osteoporosis per se is painless. Pain usually occurs in osteoporosis when there is a fracture, and this is easily diagnosed using plain x-rays. Many spinal fractures result in chronic pain.
Hip Fractures
In Singapore, the occurrence of hip fractures has been shown to be increasing. Patients with hip fractures may lose their independence, become bed-ridden and be at an increased risk of early death. Of all fractures, hip fractures cause the largest burden to society in terms of morbidity, mortality and health care costs. Because of this, the main thrust in the management of osteoporosis has been directed at preventing hip fractures.
Changes in the skeleton throughout life
Our bodies gain bone mass throughout childhood and adolescence until peak bone mass is achieved in the third decade (Fig 3). Bone mass then remains relatively constant until around the age of 40 years, and then declines in both sexes. At menopause and for several years after, women experience an acceleration of bone loss. Subsequently, the loss of bone mass in women parallels that in men.
Osteoporosis (low bone mass) may thus arise as a result of low peak bone mass, increased loss of bone or a combination of both.
Causes and Risks
Fractures occur as a culmination of a series of inter-related events. Several factors are important in determining how much bone our skeleton gains before reaching our peak bone mass. The genes one inherits play a large part. In addition, nutritional factors during growth, such as the level of calcium intake, hormones, and exercise are important.
As we grow older, the usual pattern of bone loss may be enhanced by early menopause, drugs such as corticosteroids, illnesses such as liver disease, joint disease or thyroid disease, alcohol consumption, prolonged immobilization and insufficient sex hormones in males, resulting in lower bone masses.
The background of low bone mass and poor bone architecture (or quality), coupled with the propensity to fall, puts an individual at high risk of developing a fracture.
Are you at risk for osteoporosis?
It has been found that certain people appear to be at a higher risk of having osteoporosis and therefore be at a higher risk for fractures. These people whose risk factors are listed below, should have a proper evaluation for osteoporosis.
It is generally not recommended for an individual who does not have any risk factor to undergo routine screening for osteoporosis unless that individual is particularly concerned with avoiding a fracture in future, and would be willing to be treated if he or she were found to have osteoporosis.
You should be assessed for Osteoporosis if you had:
- A previous fracture due to low impact or minor trauma
- A early menopause before age 45 years
- Undergone removal of ovaries and/or womb before age 45 years
- A prolonged period of absence of menses of more than six months duration before the age of 45 years which was not due to pregnancy
- Predisposing illnesses such as liver disease, alcoholism, malabsorption, thyroid disease, rheumatoid arthritis, hypogonadism in males
- A long-term use of corticosteroids
- A family history of osteoporosis, especially hip fracture in the mother
- A loss of height, or those who are becoming increasingly hunched
- X-rays which suggest osteopenia or 'thin bones'.
Diagnosis
As the definition of osteoporosis involves the concept of the 'amount of bone', tests have been devised to measure this. We describe these, as well as other tests which have been use in the diagnosis of osteoporosis, and discuss their roles.
X-Rays
X-rays are necessary to document fractures but cannot actually measure the amount of bone present. Bones appear to be osteoporotic on x-rays only when at least 30% of bone mass is lost. They may therefore suggest, but are not used to diagnose osteoporosis.
Bone Mineral Density (BMD)
Bone mineral density measurements give an idea of the quantity of bone present at various sites, and is the standard of measure for osteoporosis. The World Health Organization (WHO) has drawn up a classification for defining osteoporosis based on these measurements (Table 1). The T-score is a statistical score measured in SD or standard deviation units and derived from studying the local population, in which an individual's bone density is compared with the average peak bone mass of the population. The lower the score, the less bone is present, and the higher the risk for fractures.
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Table 1. WHO criteria for osteoporosis in women.
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Definition
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T-score
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Normal
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more than -1 SD
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Osteopenia
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between -1 to -2.5 SD
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Osteoporosis
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less than -2.5 SD
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Osteoporosis
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less than -2.5 SD
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Various techniques for BMD measurement are available in Singapore:
- Dual Energy X-ray Absorptiometry (DEXA or DXA) scan of hip, spine, forearm, heel
- Single Energy X-ray Absorptiometry (SXA) scan of forearm
- Quantitative Computer Tomography (QCT) scan of spine, forearm
- Quantitative Ultrasound (QUS) scan of heel
The most accepted and widely available technique for the diagnosis and monitoring of osteoporosis is the DXA scan of the hip and spine, which has the advantage of usually being performed together (Fig 5).
 The hip measurement is important in the diagnosis of osteoporosis because it gives the best prediction for hip fractures. Other techniques may indicate osteoporosis at other measurement sites, but these sites are less predictive of hip fractures than hip measurements. The spine measurement is the preferred site for monitoring how patients respond to treatment. The DXA scan of the hip and spine are available at the Singapore General Hospital.
BMD may be measured serially to assess how fast bone is being lost or how one responds to treatment. Because all techniques are somewhat imprecise, it is recommended that the intervals between scans be at least one year, preferably using the same scanner to allow for comparison.
Biochemical Markers of Bone Turnover
These are blood and urine tests which give an idea of the activity of bone in terms of bone formation and bone resorption (loss). Examples of these are serum bone-specific alkaline phosphatase and osteocalcin, and urinary deoxypyridinoline crosslinks, N-telopeptides and C-telopeptides. At present, they cannot be used to diagnose osteoporosis. These markers may be used to predict bone loss to some degree, or to monitor if patients are responding to treatment.
Preventing Osteoporosis
Healthy lifestyle measures are beneficial for the general health of the individual and are also useful for the prevention of osteoporosis. They should therefore be encouraged. There is some evidence that these primary prevention measures may strengthen bone and reduce fractures in some instances, but it is less clear whether they do so across the board.
Nevertheless, all those with a risk of developing osteoporosis should be advised on the following:
- Stop smoking
- Avoid excessive alcohol intake
- Regular weight-bearing exercise, avoiding immobility
- Nutrition
- Preventing fractures by preventing falls
Smoking and alcohol consumption
As there is evidence that both smoking and significant alcohol consumption are associated with low bone density, it is advisable to stop these.
Weight-bearing exercise e.g. brisk walking and taichi, and strength training may increase bone mass. However, exactly how much exercise is required has not been established, and the effects of exercise may be small. A reasonable recommendation is to exercise 3 times a week for 30 minutes each session. Exercise improves well-being, muscle strength and postural stability, and may reduce the risk of falls. Over-exercise to the point of having significant weight loss or menstrual disturbances, especially in young females, should be avoided. Exercise programs on a referral basis are available at the Singapore General Hospital for those with, or at risk for osteoporosis.
Nutrition
There is evidence that increasing calcium intake in young females can increase bone density, and adequate calcium intake may lessen bone loss in the elderly. The following are recommended calcium and vitamin D intakes (Table 2):
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Table 2. Recommended calcium and vitamin D intakes.
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Calcium
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male 11 to 18 years old
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1,000 mg daily
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female 11 to 18 years old
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800 mg daily
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all adults 19 years old and above
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700 mg daily
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Vitamin D
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400 IU daily
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The calcium could come from diet, dairy products or supplements if necessary (Table 3). Despite taking an adequate amount of calcium, some people, especially those with strong risk factors, may still have osteoporosis and need further evaluation. Dietary advice on a referral basis is available at the Singapore General Hospital.
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Table 3. Calcium content of some common food
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Food Type
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Standard serving size
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Calcium per portion (mg)
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Milk
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1 cup
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292
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Dried milk (non-fat)
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3 tbs
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450
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Yogurt
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1 tub
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346
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Ice cream
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1 scoop
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65
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Cheese
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1g slice
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210
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Ikan bilis (dried)
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2 tbs
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240
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Sardines (with bones)
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1 fish
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175
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Tau kwa squares
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1 large
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200
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Tau huay drink
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1 cup
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40
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Yellow dahl
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½ cup
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171
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Spinach (cooked)
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1 cup
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185
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Kai lan (cooked)
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1 cup
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284
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Chye sim (cooked)
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1 cup
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162
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Broccoli (cooked)
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1 cup
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40
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Figs (dried)
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5
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280
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Preventing fractures by preventing falls
Fractures occur as a result of weak bones, and a triggering injury, usually a fall. It is therefore useful to prevent falls. Some measures include :
- modifying the home environment by using non-slip mats, having adequate lighting, using support railings
- checking eyesight and treating visual problems
- checking for illnesses which may lead to unsteady gait and falls in the elderly
- avoiding the use of medication which causes drowsiness
- exercise to improve muscle strength and co-ordination
Treatment
There are medications available which have been used to prevent osteoporosis, as well as to treat established osteoporosis. To decide on who and whether to treat, the WHO criteria for diagnosing osteoporosis in women (Table 1) has also been used as a guide for how patients may be treated, depending on the bone density of the individual (Table 4).
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Table 4. Diagnostic categories, fracture risk and recommendations.
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Diagnostic category
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Fracture risk
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Action
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Normal
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Low
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No treatment
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Osteopenia
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Medium
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Assess bone loss serially or consider preventive drugs
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Osteoporosis
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High
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Exclude contributory causes and consider treatment
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Severe Osteoporosis
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Very high
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Exclude contributory causes and treat
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All patients should be advised on measures to prevent osteoporosis, such as lifestyle changes, and adequate calcium and vitamin D intakes should be ensured in all patients.
Before starting treatment for osteoporosis, it is important to consider if the patient may have another cause of osteoporosis which would require a different form of treatment targeted specifically at the underlying problem. The doctor would have to make an assessment and refer the patient to a specialist for further evaluation if necessary.
Treatment for Osteopenia
In patients who are osteopenic (BMD T-score between -1 and -2.5 SD), it is reasonable to see if bone loss is 'rapid' by repeating the BMD measurement in 1 to 2 years. If the fall in BMD is significant, therapy may be commenced.
Some people may prefer to start on medication for the prevention of osteoporosis immediately, but it is not yet clear whether fractures are actually reduced by intervening at this stage. These drugs include:
- Hormone replacement therapy
- Bisphosphonates such as alendronate or etidronate
- Tibolone
- Raloxifene
Treatment for Osteoporosis
Drugs for the treatment of osteoporosis are advisable in patients who are osteoporotic (BMD T-score less than -2.5 SD) and are strongly advised in those who have had low impact fractures. These drugs have been shown to reduce fractures at various sites but differ in how effective they are. These drugs include:
- Hormone replacement therapy
- Bisphosphonates such as alendronate, etidronate and clodronate
- Calcitonin
- Vitamin D analogs such as calcitriol and alphacalcidiol
- And other agents eg anabolic steroids
Choice of therapy
The choice of drugs depends on which therapy is:
- Most indicated depending on the patient's medical history
- Most acceptable to the patient in terms of side-effect profile, compliance and cost
- Patients would need to discuss with their doctor the various merits and problems before deciding on treatment. There is little data on the effectiveness of these medications in men with osteoporosis.
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Drugs available for the prevention of osteoporosis
• Hormone Replacement Therapy (HRT)
At this time, HRT remains the "gold standard" for the prevention of osteoporosis. All women should receive advice about the benefits and risks of HRT at the time of menopause so that they can make an informed decision about its use. There is evidence to suggest that HRT is useful for preventing osteoporosis, treating menopausal symptoms, such as urinary and genital problems, and reducing heart problems. However, a recent study has suggested that HRT should not be started in women who already have heart disease. The risks of HRT include an increased risk of breast cancer and venous thromboembolism.
• Bisphosphonates
This group of drugs includes etidronate, which is prescribed in a cyclical regimen, and alendronate. Both medications preserve or increase bone density compared to patients given a placebo. However, it remains unclear whether fractures are prevented. Alendronate for the prevention of osteoporosis (5 mg/day) is not yet available, but would probably be so in the near future.
• Tibolone
Tibolone is a synthetic steroid with mixed estrogenic, progestogenic and androgenic effects. It appears to be useful in preventing hot flushes and increases bone density, but its effects on fracture rates and cardiovascular disease are less clear.
• Raloxifene
Raloxifene is a selective estrogen receptor modulator which appears to decrease the risk of breast cancer and have estrogenic activity on bone. Fracture efficacy has yet to be reported and it is currently not available.
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Drugs available for the treatment of osteoporosis
In various trials, most of these agents result in increased or maintained bone densities compared to placebo groups. The anti-fracture efficacies vary, as do the considerations for their use.
• Hormone Replacement Therapy (HRT)
Estrogen alone or with a progestogen increases bone density at the spine and the hip. There is a reduction in the risk of spine fractures and epidemiological evidence for reduced hip fractures. It has been suggested that there is no age limit for HRT. HRT could be prescribed either in a cyclical or continuous fashion, and the various benefits and risks need to be discussed with the doctor.
• Bisphosphonates
Both bisphosphonates, alendronate and etidronate are available in Singapore. In several large well-designed trials, alendronate increased BMD at the spine and at the hip. More importantly, it was demonstrated to reduce the risk of fractures at all sites including the hip. However, alendronate 10 mg is poorly absorbed and may cause esophageal ulceration, which is a fairly serious complication. It must be taken at least 30 minutes before food, drink or oral medication, with a full glass of water, and the patient must remain upright for 30 minutes after each dose. Etidronate, prescribed in a cyclical regimen, increased bone density in the lumbar spine with reduced risk of vertebral fractures. One epidemiological study suggested a decrease in limb fractures including those at the hip. Etidronate should be taken at the mid-point of a 4 hour fast. It is prescribed as a two week course of 400 mg om followed by calcium carbonate 625 mg bd for eleven weeks, after which the cycle is repeated.
• Calcitonin
Calcitonin may increase BMD and has been shown to reduce vertebral fractures, but a reduction in hip fractures has not been demonstrated. This drug can only be administered intranasally or through injections. Calcitonin appears to have some analgesic properties which may be useful in painful compression fractures.
• Vitamin D analogs
These have been shown to decrease loss of bone in post-menopausal women with osteoporosis, but a decrease in vertebral fracture frequency has not been a consistent finding, and no protective effect has been shown for hip fractures. Calcium supplements should be stopped when using these analogs.
• Other agents
Anabolic steroids may increase BMD and may be used in frail, elderly patients to improve well-being and increase muscle strength. Its anti-fracture efficacy is weak. Other therapies which are currently unavailable include fluoride, and newer therapies such as raloxifene, parathyroid hormone and ipriflavone.
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