Osteoporosis has been described as the 'silent epidemic'; by the time it causes symptoms, considerable bone has quietly disappeared. For all its apparent solidity, bone is not inert but is constantly being formed and broken down or resorbed.
Osteoporosis occurs when breakdown (resorption) is greater than formation, just as debt follows when expenses exceed income. The internal structure of bone changes, becoming less dense and leading to fragile bones which are more easily broken - hence the lay term 'brittle bone disease'.
Though treatments can halt further bone loss , it is much harder to reverse established osteoporosis. By the time the condition is obvious clinically, the density of the bones has usually dropped significantly. Bone density can be estimated by scans, but the catch is that not everyone gets a scan in time to get most benefit from treatment.
The consequences Patients with osteoporosis can break bones even with negligible trauma, such as slipping in the bath or even undressing. Every year in the UK, there are roughly 70,000 hip fractures (or more correctly, fractured necks of femur), 50,000 wrist fractures (usually called Colles' fractures) and 40,000 vertebral fractures - all due to osteoporosis.
Although as many as half of all hip fracture patients are under 70, fractures generally increase with age, posing enormous problems for secondary care. I remember one icy January day on which 19 elderly people slipped and sustained Colles' fractures. Within a few hours all passed through the same accident and emergency department and many were admitted to hospital.
Fractured hips are even more problematic (see box 1), and the human cost begins with the need for immediate care. In 1995 the Audit Commission estimated that nearly 20 per cent of hip fracture patients wait more than five hours in A&E, and nearly 60 per cent wait two or more days for surgery - in bed, and in pain.
The financial burden of osteoporosis to the UK government and the NHS is around£942m a year.
Unsurprisingly, hip fractures account for about 90 per cent of the cost of care. However, the long-term result is not always good. While most patients survive surgery, only 45 per cent ever go home again. Six months after hip fracture, only around 20 per cent of patients can walk unaided, so many need long-term nursing home or hospital care. Further breaks can complicate matters, and about 40 people a day die following fractures caused by osteoporosis.
A fracture of one or more vertebrae rarely brings a patient into hospital, but it can cause great pain, as well as the typical shrinkage that affects elderly people and the 'dowager's hump' of older women. In some, the spine collapses to such an extent that the ribcage practically rests on the pelvic bones, bringing digestive and other symptoms.
Who is vulnerable?
Bone loss increases with age, starting around mid-life. Typically, 'little old ladies' get osteoporosis because oestrogen, which plummets at the menopause, has a strongly positive effect on bone formation. The menopause is the single most important cause of osteoporosis.
However the condition can occur in anyone whose bone loss exceeds formation, and affects younger women and men too.
Many factors increase the risk:
genes (family history of osteoporosis) race (Afro-Caribbeans rarely get osteoporosis, but white races are very prone) menopause or hysterectomy before age 45 long-term steroid treatment (eg for asthma or after organ transplant) anorexia nervosa over-exercise (as in elite female athletes) inadequate calcium intake long-term immobility excess alcohol smoking.
All these either speed up bone loss, or affect the peak bone mass achieved in early adulthood. Without exercise to stimulate production, and a good supply of calcium to feed them, bones weaken. But excessive exercise can have the opposite effect, especially in younger women as it suppresses their normal hormonal cycle. Weight is also important - we now know fat is metabolically and hormonally active so, though it is too late to tell Wallis Simpson, one can be too thin.
Thanks largely to the National Osteoporosis Society, public and professional awareness has increased.
Doctors now more often consider osteoporosis, especially when a fracture follows only minor trauma.
But while plain x-rays are ideal for revealing fractures, they are poor at detecting osteoporosis - which is where bone densitometry (also called DEXA scanning) comes in.
DEXA (dual energy x-ray absorptiometry) uses little radiation and is sensitive and fairly quick. But each machine costs around£15,000£20,000 and provision is poor in the UK compared with the rest of Europe.
It varies geographically, too; GPs can refer patients for DEXA scanning in some areas, while in others a consultant must request the test. And because DEXA equipment is made by a number of manufacturers, measurements can vary from one machine to another.
Bone density measurement is still very useful, especially to monitor treatment progress, but at the moment it is difficult to decide who should have one in the first place.
DEXA is not suitable for mass screening, and there is no point scanning elderly patients with several fractures - we know they have osteoporosis. There is little value in Yscanning women with a normal menopause and no added risk factors.
Other tests of bone density are in the pipeline. Quantitative ultrasound measures ultrasound velocity in a bone (usually the heel) and may prove useful in the future. Soon to be launched is a urine-testing kit from Cortecs Diagnostics that will detect levels of a biomarker associated with bone loss. This may cost only£150 for the device and£15 for testing each sample and could prove to be a quick bedside test - though it remains to be seen if it is as reliable as it is convenient.
Treatment and prevention There are many treatments used for osteoporosis, including supportive painkillers and surgery where needed (see box 3).
Preventive measures include lifestyle changes (more exercise, more calcium, less alcohol, no smoking), as well as treatment with hormone replacement therapy and biophosphonates.
Not surprisingly, there is debate and confusion about how energetically one should look for and treat or prevent osteoporosis. Department of Health guidelines for GPs are expected soon, focusing on five main areas:
identifying those with osteoporosis or at high risk of it identifying causes of osteoporosis encouraging lifestyle changes choosing long-term therapy for prevention and treatment patient referral.
Not before time - but guidelines cannot be implemented without funding, particularly in diagnosing osteoporosis.
On the horizon Things promise to become even more complex.
Biophosphonates, currently given orally, are poorly absorbed by mouth, so the search is on for new ones, as well as patches and nasal sprays of existing products.
Another exciting area is the development of SERMst (Selective oEstrogen Receptor Modulators), which seem to activate a gene that promotes bone growth. Raloxifene is one such 'designer oestrogen' which, unlike HRT, may work selectively on oestrogen receptors in bone, heart and brain without affecting breast or uterus. Raloxifene could enable the prevention or treatment of osteoporosis without the inconvenience of bleeding or breast tenderness that women dislike, or the more serious risks like breast cancer.
Studies show that two years' treatment with this drug appreciably increases bone density.
Availabe in the US since early this year, raloxifene is expected to come on to the UK market soon. Recently released trial results in the US suggest it may also reduce heart disease, and conceivably Alzheimer's and breast cancer too.
But as with other osteoporosis drugs there are two key questions: who could benefit most from treatment, and who will be lucky enough to receive it?
Carol Cooper is a Hertfordshire GP.
An estimated 3 million people have osteoporosis in the UK
One woman in three will develop it
After the menopause, bone is lost at the rate of 3 per cent or more a year
By the time symptoms occur, around one-third of bone mass has been lost
Every three minutes, someone breaks a bone through osteoporosis
About one orthopaedic bed in three is currently occupied by a fracture due to osteoporosis
Box 1. Surgery for fractured hips - one of the consequences of osteoporosis
The way arteries are arranged in the femoral head demands surgical intervention for fractured neck of femur. So, whether the break is sub-capital (just under the head of the femur) or inter-trochanteric (lower down on the neck), an operation is usually the only answer. An inter-trochanteric fracture needs a pin and plate, while a sub-capital fracture requires full replacement of the head (by an Austin-Moore or similar prosthesis) - unless the hip joint is already arthritic, in which case a total hip replacement, of both ball and socket, is in order.
Box 2. Why is osteoporosis on the rise?
Hip fractures, which can be used as a marker for osteoporosis, continue to grow at the rate of 6 per cent a year, so osteoporosis really is increasing. With life expectancy about 80 years for women and 75 years for men, people are living longer, but this is not the whole reason for the rise, and osteoporosis probably has its roots early on in life.
Childhood and the teen years are crucial to forming strong bones. Unfortunately many young people have a sedentary lifestyle based around TV and the computer at home, punctuated by car rides to and from school, where games are vanishing from the timetable.
In Britain, PE lessons take up on average 106 minutes a week, about half that spent on exercise by French schoolchildren. The usual teenage diet is poor: most girls get way below the recommended daily intake of 1,000mg of calcium, and fizzy drinks contain high levels of phosphorus, which make it harder for the body to absorb what little calcium is on offer. The result? A skeletal bank balance that is not substantial enough to last once bone loss begins in earnest at 30-something.
However, many mysteries remain, such as why some pregnant women get osteoporosis. Though it may be transient, it can cause great pain and may even fracture vertebrae. Osteoporosis can strike during pregnancy or in the two to three months after delivery, creating problems in caring for the new baby.
Then there is osteoporosis in men. Around a fifth of hip fractures occur in males and the incidence is rising. Men generally have thicker, heavier bones than women, but some may have genetic reasons for failing to achieve a good peak bone mass.
A few have medical conditions demanding long-term steroid therapy or causing low levels of male hormones: testosterone, like oestrogen, stimulates bone formation and levels of this hormone can drop, even if the existence of a male menopause is debatable.
There are also lifestyle factors like drinking, smoking, poor diet and lack of exercise, but in many men it is not clear why their bones are porotic.
Without doubt, more work is needed on the 'little old ladies' disease', which is causing increasing symptoms and disability in both sexes.
The National Osteoporosis Society has published a patient booklet on male osteoporosis, as well as many other publications for patients and professionals. Write to PO Box 10, Radstock, Bath BA3 3YB (tel: 01761-471771; patient helpline, 01761-472721).
Box 3. Treatments used for osteoporosis
Hormone replacement therapy (HRT) HRT, the most widely used treatment, is given orally, in patches or as topical gel implants. HRT stimulates bone formation, probably by activating oestrogen receptors in bone tissue. It can reduce the risk of osteoporosis by 60 per cent; it also increases life expectancy by up to three years (probably mainly by reducing coronary artery disease).
Some experts regard the menopause as an oestrogen-deficiency disease. Since osteoporosis (and cardiovascular disease) can kill, they may have a point. But should one give the entire post-menopausal population longterm HRT, which is what would be needed to stave off osteoporosis for any length of time?
And there is no gain without pain. The extra risk of breast cancer after 15 years on HRT is 12 per 1,000 patients, while the risk of dying from deep vein thrombosis and its complications is around three times higher than without HRT - though the absolute risk is still low at around 3 per million a year.
Weight gain, breast tenderness and withdrawal bleeds put some women off - of the 10 per cent prescribed HRT nearly half give up within a year.
Biophosphonates Biophosphonates are synthetic pyrophosphates, given orally to slow down bone resorption. They are increasingly being used as primary prevention.
Of the many biophosphonates, etidronate, which mainly helps the spine, is given in three-month cycles, and alendronate in a continuous daily dose. Studies are not strictly comparable, but alendronate may be more potent and seems to work on the hip and wrist too.
FIT (the Fracture Intervention Trial), the largest osteoporosis study ever, found that alendronate reduces the incidence of new spine fractures by 47 per cent, wrist fractures by 48 per cent and hip fractures by 51 per cent.
5Work also suggests that increases in bone mineral density with alendronate are as great as with combined HRT.
6Calcitonin A natural hormone (given by injection) that inhibits bone resorption, but is mainly used to treat the pain of osteoporotic fractures.
Calcitriol, and calcium and vitamin D supplements Calcitriol is the active form of vitamin D which enhances absorption of calcium from diet and its use in the body. Calcium and vitamin D combinations have a similar effect but are adjuncts to therapy. Both treatments are given orally.
Male osteoporosis Osteoporosis affects about one man in 12 in the UK A man aged over 50 has a 10 per cent chance of an osteoporotic fracture Loss of height is even more common than in women In a fifth of cases, osteoporosis is due to low testosterone levels. In others, alcohol may be a significant factor In 45 per cent of osteoporotic men, the cause is unknown - so-called idiopathic osteoporosis.
There is no established therapy for idiopathic osteoporosis in men
1 Delmas P, Bjarnason N, Mitlak B, et al. Effects of raloxifene on bone mineral density, serum cholesterol concentrations and uterine endometrium in postmenopausal women. New England J of Medicine 1997; 337(23): 1641-47.
2 Col N, Eckman M, Karas R, Pauker S et al. Patient-specific decisions about hormone replacement therapy in postmenopausal women. J of the American Medical Association 1997;277(4): 1140-47.
3 McPherson K. Breast cancer and hormonal supplements in postmenopausal women, Br Med J 1995;311(7007): 699-700.
4 Daly E, Vessey M, Hawkins M et al. Risk of venous thromboembolism in users of hormone replacement therapy. Lancet 1996; 348(9033): 977-80.
5 McClung M, Clemmesen B, Daigotis A et al. Alendronate prevents postmenopausal bone loss in women without osteoporosis. Ann Intern Med 1998; 128(4): 253-61.
6 Hosking D, Chilvers C, Christiansen C et al. Prevention of bone loss with alendronate in postmenopausal women under 60 years of age. New England J Medicine 1998; 338(8): 485-92.