The rough and tumble of diving increases risk of bone fractures
By Dr. David Sawatzky
Osteoporosis is a very common bone disease that increases the risk of fractures and diving is an activity where trauma is relatively common. The condition is more prevalent as we age and divers are becoming older on average. So let’s take a look.
Osteoporosis reduces Bone Mineral Density (BMD). A BMD that’s 2.5 standard deviations less than the average found in young healthy adults is how the World Health Organization (WHO) defines this condition. Bone microarchitecture deteriorates in osteoporotic bone, altering protein amount and variety; such changes weaken the bones and make them much easier to break. Most frequently broken are the hip, spine and wrist bones.
BMD peaks at an average age of 25 years and then declines. Women are much more likely to have osteoporosis than men, and Caucasian and Asian racial groups are more likely to develop osteoporosis than others.
Here’s an occurrence frequency snapshot.
Caucasian women in the USA:
Age 50-59 14 per cent
Age 60-69 22 per cent
Age 70-79 39 per cent
Age 80+ 70 per cent
Approximately 80 per cent of people with osteoporosis are women. In the 50+ demographic, fractures due to osteoporosis will occur in about 50 per cent of women and 12.5 per cent of men in their lives.
Many people think bone is dead and static. The truth is that bone is very much alive and active.
At any point in time cells called osteoclasts absorb bone and cells called osteoblasts produce new bone.
Osteoporosis develops by three primary mechanisms. First, the total amount of bone in our bodies increases from birth until about age 25, and thereafter that bone mass slowly declines. Second, if enough bone is not made by age of 25 ‘peak bone mass’ will be less than it should, increasing the likelihood of osteoporosis later in life. And third, if bone is resorbed faster than normal and/or if new bone is laid down slower than normal, there’s an increased risk of developing osteoporosis.
There are several factors that influence the rate of bone resorption and deposition. Estrogen limits the rate of resorption and stimulates deposition of new bone. Therefore, in women after menopause, when estrogen production declines sharply, bone is absorbed faster and laid down more slowly, resulting in a more rapid reduction in BMD. Women who are too thin or who exercise to excess (or both) often stop having periods due to a reduction in the amount of estrogen they produce. A relative lack of estrogen over a long period increases the risk of developing osteoporosis later in life.
A diet low in calcium and vitamin D slows the rate of bone deposition. As well, calcium is needed for many other body functions so if there isn’t enough calcium in the diet, extra parathyroid hormone is produced causing calcium to be removed from bone to maintain the required level of calcium in the blood. The hormone calcitonin is produced by the thyroid gland and it increases bone deposition, however, its role in osteoporosis is less clear.
Testosterone also influences the rate of bone resorption and deposition so the decline in testosterone levels in men after age 70 increases the risk of osteoporosis.
Some drugs increase the risk of osteoporosis. Corticosteroids (prednisone, methylprednisolone) if taken daily for more than three months, some antiseizure drugs, anticoagulants, proton pump inhibitors, antacids, and some oral diabetic drugs can cause osteoporosis.
Stressing bones with gravity and exercise stimulates bone formation. NASA has done a lot of research to develop exercises astronauts can do in space to counteract the rapid loss of bone that occurs in the absence of gravity. Immobilization for any reason (wheelchair) increases the risk of osteoporosis.
From the preceding information it should be obvious that everyone should ensure that they have adequate calcium in their diet, that they eat or generate enough vitamin D (it is made in the skin with sun exposure), and that they do enough weight bearing stressful exercise on a daily basis to maximize bone formation and reduce bone resorption.
Smoking, excessive alcohol consumption and being small/thin also contribute to the development of osteoporosis. One of the very few advantages of being obese is that it reduces the risk of osteoporosis (an obese person stresses their bones every time they’re moving their own mass around). Finally, a family history of osteoporosis, hyperparathyroidism, and hormone treatment for prostate or breast cancer raises the risk of osteoporosis. The preceding are the most common causes of osteoporosis but there are many more.
A person with osteoporosis has no symptoms until very late in the disease process at which time they can develop fractures of the hip, spine or wrist, often with very little trauma. They can experience bone pain or tenderness, a loss of up to six inches (15cm) in height, pain in the neck and/or back, and a stooped posture , or kyphosis, due to spinal fractures that cause the fronts of the vertebral bodies to collapse, turning a ‘block’ into a ‘wedge’.
Avoiding osteoporosis is the best strategy. A healthy lifestyle from your teen years onwards will dramatically reduce the chance of developing osteoporosis.
Dealing With It
Osteoporosis is diagnosed with a ‘bone density test’ administered – ideally – before suffering a fracture due to osteoporosis. Those at risk, such as women over age 65, women who weigh less than 155 pounds (70kg), should arrange through their doctor to be tested. If you have osteoporosis, there are several treatment options.
The goals of treatment are to control pain, slow down or stop bone loss, prevent fractures by making the bone stronger, and to minimize the risk of falls that might cause fractures. Medications are used if a person has osteoporosis, or if the individual has suffered a fracture and shows reduced bone density on testing, even if it’s less than the 2.5 standard deviations required to diagnose osteoporosis, as mentioned at the outset. This condition is called ‘osteopenia’.
A good diet and daily exercise are very effective improving BMD and in preventing falls, so attention to them is key.
Estrogen and testosterone replacement for people who are deficient is beneficial for preventing and/or treating osteoporosis, though there is no benefit if levels of these compounds are normal. Estrogen replacement in post-menopausal women has been linked to other problems so a careful risk-benefit analysis is essential beforehand.
Biphosphonates (alendronate, ibandronate, risedronate) are effective and reduce the risk of fractures by 25 to 70 per cent. Calcium and vitamin D reduce the risk of non-vertebral fractures by roughly 20 per cent. Several other drugs are also used at times.
How about osteoporosis and diving? Diving is associated with a risk of ‘osteonecrosis’. Osteonecrosis is really a form of untreated or inadequately treated decompression sickness and has a completely different pathogenesis from osteoporosis.
Osteonecrosis on top of osteoporosis could be serious; a person with osteoporosis has altered bone structure and ‘may’ be at increased risk of osteonecrosis so anyone with osteoporosis should dive very conservatively to reduce the risk of decompression sickness to near zero.
Diving removes the effect of gravity and therefore reduces the stress on our bones. If we were to spend enough time in the water this might increase the risk of developing osteoporosis. A 2004 study suggested professional scuba divers had a reduced BMD compared to a group of non-diving controls. A 2011 Polish study found no difference in BMD of professional divers and matched controls. They also found no relationship between total diving time in hours and BMD. Other studies have produced conflicting results. This is not entirely surprising considering that divers also get a fair amount of weight bearing exercise carrying heavy gear around, a factor that would increase BMD. The bottom line is that diving does not seem to contribute to the development of osteoporosis.
If a person has osteoporosis and wants to take up or continue diving, there are a few things that should be taken into consideration. Diving is associated with a significant risk of falls and trauma. We tend to carry heavy things around, often on very unstable platforms (boats) and/or over very rough ground. This greatly increases the risk of a fall or serious bang and with osteoporosis such trauma could easily break a bone. So, if a person with osteoporosis wants to dive, they should be very careful to limit this risk. Getting help to move gear on and off a boat or over rough ground makes sense though carrying it over smooth ground provides exercise that will help strengthen bones. Resistance exercise also will make a person stronger and less likely to fall.
A person with osteoporosis may take up or continue diving but should be careful and aware of the risks involved. Everyone, divers included, should minimize the risk of developing osteoporosis through appropriate changes in lifestyle. Anyone at risk of having osteoporosis should be tested.
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