People with cystic fibrosis (CF) are at risk of developing osteopenia and osteoporosis. These are both forms of bone disease marked by loss of bone mineral density — meaning the bones lose minerals like calcium, which makes them weaker and more easily broken.
Osteopenia is a relatively milder loss of bone mineral density, whereas osteoporosis is a more severe loss. Osteopenia generally happens before osteoporosis. It can happen at any age, but in people with CF, it is more common during the late teens and in adults. It’s estimated that nearly one in three adults with CF have bone disease.
Causes of bone disease in CF
CF-related osteopenia and osteoporosis can develop due to a multitude of different interconnected factors.
For example, many people with CF have problems with digestion that can make it hard to absorb certain vitamins, such as vitamin D. Low vitamin D intake can increase the risk of developing osteoporosis because vitamin D helps the body absorb calcium, which is an essential mineral for healthy bone density.
More generally, because of digestive problems, many people with CF have poor nutrition, and may struggle to consume enough calories to keep their bodies functioning properly. Poor nutrition — especially in childhood and adolescence — can lead to poor bone growth.
People with CF are at increased risk of certain lung infections. Chronic infections — and the inflammation that happens as a result — can interfere with normal bone growth and maintenance, which may increase the risk of osteopenia and osteoporosis.
Substantial bone growth occurs during puberty. The combination of poor nutrition and repeated infections can slow puberty in people with CF, which also is tied to the risk of bone disease.
An active lifestyle — and, in particular, weight-bearing exercise — is important for maintaining bone health. However, people with CF may have trouble being regularly active when they are chronically ill or having trouble catching their breath.
It’s important to note that nutrition, lung disease, activity, and bone health are all related. When people do not feel well, they often will eat less and become less active, which leads to weaker muscles and bones.
Certain medications, such as corticosteroids and others that weaken the immune system, may increase the risk of osteopenia and osteoporosis. Other factors that can increase the risk of osteoporosis in people with CF include diabetes, alcohol use and smoking. It has been suggested that mutations in the CFTR gene itself, which is the cause of cystic fibrosis, may influence the development of bone disease.
Detecting bone disease
Screening for osteoporosis and osteopenia is done by checking height and weight. Development during puberty also is tracked, and people with CF should have their vitamin D levels checked and be screened for diabetes every year.
Dual-energy X-ray absorptiometry, or DEXA, is a test that uses X-rays to measure the density of the bones, and is used to detect osteoporosis. DEXA results are reported as T-scores and Z-scores; a T-score of -1.0 to -2.5 indicates osteopenia, and a score of less than -2.5 indicates osteoporosis. It’s recommended that people with CF undergo DEXA screening by age 18.
Managing bone diseases
Prevention is the best defense against developing osteoporosis. This includes a healthy lifestyle, with adequate food intake and supplementation. Daily activities and exercise, especially weight-bearing exercise, are important, too.
In people who do develop osteoporosis, proper nutrition — in particular, making sure patients get enough vitamin D and calcium — is key. Depending on the severity of the disease, bisphosphonates may be prescribed to enhance new bone growth.
Last updated: Sept. 8, 2021
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