As we grow older our bones become thinner and more fragile. Having IBD may make developing weaker bones more likely. This three part series of articles provides information for anyone with Ulcerative Colitis (UC) or Crohn’s Disease (the two main forms of IBD) who may be worried about developing fragile bones. It looks at why this may happen, and recent developments in prevention, diagnosis and treatment.
What causes bone loss?
Some loss of bone density happens naturally with age. The process of bone formation slows down and bone resorption begins to outpace bone formation, so our bones become less dense. During childhood and early adult life, bone density, also known as bone mass, increases, reaching a peak at around age 25-30. After this, bone mass generally declines gradually as part of the natural aging process. Normal peak bone mass may never be reached if a disease affects bones during early life. Bones can also lose density if there is insufficient calcium in the body to form enough bone tissue. A shortage of sex hormones (oestrogen and testosterone) can lead to a reduction in bone formation. Lack of exercise may also result in increased bone loss because regular impact or weight-bearing exercise stimulates the body to strengthen the bones.
Why does loss of bone density matter?
Bone density is sometimes known as BMD (bone mineral density) and is usually measured by a DEXA scanner (see below). Having a serious loss of bone density, or a low BMD measurement, does not automatically mean that your bones will break. But it does generally mean you are at greater risk of fracturing (breaking) a bone. Thin bones are not in themselves painful, but fractures usually are, and some, such as hip or spine fractures, can lead to a serious loss of mobility.
How can I tell if I have loss of bone density?
Perhaps surprisingly, there are usually no obvious symptoms of bone loss apart from fractures. So, the best way of working out how likely you are to be affected is to consider how many of the main risk factors may apply to you.
What are the main risk factors?
For the general population, the main factors associated with a higher risk of developing bone loss are:
- Age – although loss of bone density can affect any age group, it is most common in the elderly.
- Gender – women have smaller bones and tend to lose bone faster than men. This is because hormonal changes during the menopause accelerate the breakdown of bone. Younger women who have been through an early menopause may also be more at risk.
- Ethnic background – people of Caucasian or Asian race appear to be more likely to develop bone loss.
- Genes – having a family history of osteoporosis or fractures.
- Previous fractures – if you have already broken bones easily you are more likely to have fractures in the future.
- Low body weight - people with a low weight may have finer and smaller bones.
- Smoking.
- Drinking too much alcohol.
- In men, low levels of testosterone.
- Poor diet – if it is low in calcium or in vitamin D, which helps the body absorb calcium.
- Long-term immobility or an inactive lifestyle (for example, being housebound).
What are the additional risks if you have IBD?
Research has suggested that having IBD is another factor that may make bone loss and fractures more likely. For example, people with Crohn’s Disease appear to be about one and a half times more likely to break a hip than people in the general population. The increased risk for people with UC is slightly lower, but still significant.
Why are people with IBD at extra risk?
Several factors might be contributing to this increased risk.
- The use of corticosteroids (‘steroids’)
Treatment of UC or Crohn’s Disease with steroids can increase the risk of having weak bones. This is because steroids can decrease the rate at which the bone-building cells work, thus accelerating bone loss. Steroids can also affect the amount of calcium absorbed from food, and increase the calcium lost from the body in urine. How seriously the bones are affected usually depends on the dose and length of steroid treatment.
Steroids taken rectally (in enemas or suppositories) are less likely to cause one weakness than steroids taken by mouth, because they are not so easily absorbed into the blood.
- Avoidance of dairy foods
If you avoid dairy products, perhaps because of lactose (milk sugar) intolerance or abdominal pain, you are more likely to have a shortage of calcium in your diet, unless you are taking a regular supplement. This shortage can slow down bone formation.
- The inflammatory process itself
People with active IBD tend to have a higher level of cytokines (hormone-like proteins), which are released as part of the inflammatory process. These chemicals can affect the rate at which new bone is formed.
- Poor absorption of nutrients because of inflamed intestines
The nutrients important to bone formation, especially calcium and vitamin D, are absorbed in the small intestine. So if you have extensive Crohn’s, or have had parts of your small intestine removed, you may be at additional risk.
In part 2: How is Bone Loss Diagnosed and Treated?
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