What is osteoporosis?
Osteoporosis is the process of loss of calcium from bone with consequent fragility and increased risk of fracture. We start to lose bone strength from the age of about 35 and the loss continues throughout life but becomes more rapid in women after the menopause.
Our bones are not inert struts to support our carcasses – they are living structures which continually renew themselves to maintain their functional strength. Old bone is constantly being replaced by new. Weight bearing is needed to promote this process.
What causes osteoporosis?
As we age our bones become weaker with loss of the main bone mineral which is calcium. Reduction in “anabolic” hormones, mainly oestrogen and testosterone, accelerates this process. This is most obviously seen in post menopausal women who are the main victims of this condition as their oestrogen production falls off a cliff. Cigarette smoking, being underweight and inactivity are other risk factors. A dramatic loss of bone is seen in astronauts, resulting from their weightlessness in space.
How is it measured?
Moderate to severe osteoporosis usually shows up on straight X-rays, as may be done to check for fractures or joint problems. The severity of osteoporosis is more accurately examined by a special bone scan – the “DEXA scan” which measures the bone mineral density (BMD). This test also identifies osteopenia which is a loss of bone mineral less severe than osteoporosis and which has a high probability for progressing to osteoporosis in time. DEXA scans are particularly useful for picking up mild degrees of osteoporosis and for tracking the progress of the condition.
What harm does it do?
About 3 million people in the UK have osteoporosis and they suffer more than 300,000 fragility fractures annually. These include such horrors as broken wrists and hips and crush fractures of the spine. These lead to temporary or sometimes permanent dependency and often to shortening of life. Hip fractures alone occupy 1.3 million hospital bed days and cost the English economy £1.5 billion annually. Post-menopausal women are particularly susceptible though men are far from immune.
Exercise in the prevention of osteoporosis
The best way of preventing osteoporosis is weight bearing exercise, particularly “impact” exercise like running or skipping. Population studies involving athletes confirm this and indicate that high impact sports such as running, squash, and weightlifting lead to an increase in BMD, whereas low impact sports such as swimming do not.
For the spine and lower limbs, weight bearing exercise is what does the business. The earlier exercise is started the more effective it is.
And the prevention of fractures
A really important question is whether exercise reduces the risk of osteoporosis-related fractures, particularly of the hip or vertebrae which can be so devastating for the sufferer. No intervention study has assessed the effect of exercise on the rate of osteoporotic fracture. That is to say no one has carried out a randomised controlled trial of exercise versus no exercise to show that the exercised group has a lower long-term risk of fracture – such a trial would be extremely difficult to perform.
However observational studies have indicated a strong protective effect. 3262 healthy men (mean age 44 years) were screened for exercise habit and followed for 21 years. Intense physical activity at baseline was associated with a reduced incidence of hip fracture, to just 38% of the risk for the non-exercisers. Another study from the USA reported that women who had a high frequency of participation in outdoor sports had only 30% the chance of suffering a hip fracture compared with those with a low frequency of participation. As one reviewer wrote: “… physical inactivity is currently proffered as the most salient explanatory factor for the increasingly high hip fracture rates reported by developing countries, as well as many first-world countries”.
Cochrane in 2011 reviewed the evidence for the role of exercise in preventing osteoporosis and related fractures in post-menopausal women. They found a small but important reduction in osteoporosis from exercise programmes – resistance strength training being most effective in protecting the hip and combination exercise for the spine. For the women studied the overall fracture rate was 11 per hundred in those who did not exercise compared to 7 per hundred for those who did – a saving of 4 fractures for every hundred exercisers.
Exercise for treating osteoporosis
A definitive assessment of the effectiveness of exercise in treating osteoporosis was published in 2012. After analysis of 74 trials the authors concluded that aerobic exercise and weight training do increase bone mass or at the very least reduce the rate of bone loss in osteoporotic (mostly post-menopausal) women. They found that the lower the BMD the more effective was the exercise as a treatment. “The best improvements seem to be achieved through strength training of high-loading intensities with 3 sessions per week and 2–3 sets per session. Although significant effects can be observed after 4 or 6 months in some locations of the body, the efficacy of the training programme is greater when it extends for at least 1 year”.
Regular weight-bearing exercise has a two pronged benefit in osteoporosis. Firstly the exercise slows or reverses the loss of bone mineral. Secondly it reduces the risk of falls thus reducing the risk of fractures for those with bones weakened by osteoporosis.
The National Osteoporosis Society produces a 60 page booklet of exercise advice for osteoporosis prevention and treatment (https://www.nos.org.uk/health-professionals/~/document.doc?id=770).
A quote from Bill Bryson’s splendid book “The body”:
“Our bones lose mass at a rate of about 1 per cent a year from late middle-age onwards, which is of course why elderly people and broken hips are so unhappily synonymous. Broken hips are especially challenging for the elderly. About 40 % of people over seventy five who break their hips are no longer able to care for themselves. For many it is a kind of last straw. Ten percent die within 30 days and nearly 30% die within 12 months. “We enter the world through the pelvis and leave it through the hip” Astley Cooper