Asthma is a disease of the lungs, not the bones. There are no bones in our bronchial tubes, right? So where is the connection?
The most important connection relates to the anti-inflammatory steroids ("corticosteroids") used to treat asthma. Prednisone and methylprednisolone (Medrol), if taken regularly or for many months of the year, can have major effects on the bones. In children they can impair bone growth, leading to lesser height as an adult. In adults steroids can decrease bone mass and predispose to the thinning of the bones called osteoporosis. Osteoporosis is a condition without symptoms but one that predisposes to fractures, sometimes with minimal or no trauma. Osteoporosis can cause vertebrae to collapse in on themselves (vertebral compression fractures), ribs to break with coughing or twisting, and hips to break when we fall.
Because of these and many other negative effects of corticosteroids taken as tablets (and distributed via the bloodstream to all parts of the body), safer alternatives to treat the inflamed airways of asthma were developed. In the 1960s corticosteroids that could be delivered directly to the bronchial tubes in the form of medication aerosols became available. The first widely used formulation was beclomethasone by metered-dose inhaler. Since then other corticosteroid preparations have become available, some as metered-dose inhalers, some as dry-powder inhalers, and one as a solution for nebulization. These medications are given in a small fraction of the dose of oral steroid tablets, and only a small portion of the inhaled medication makes its way into the bloodstream, to be carried to the bones and elsewhere throughout the body. As a result inhaled steroids are far safer for the bones than oral steroids.
And yet. A small portion of the inhaled steroid can be absorbed into the blood and carried to the bones. If the dose of inhaled steroid is high enough and the duration of use long enough, it is possible that over a period of several years steroids by inhalation, like steroids swallowed as tablets, can have some effect on bone health. And for many people, it is not an either-or proposition. Many people require daily inhaled steroids for control of asthma plus occasional bursts of oral steroids to reverse flare-ups or asthma attacks.
The potential risk to your bones from long-term use of high doses of inhaled steroids does not mean that you should stop using your steroid inhaler. In most instances, inhaled steroids prevent or reduce the need for oral steroid tablets, which have a far greater impact on your bones. Rather, it means that we -- patients and healthcare providers alike -- need to be vigilant about maintaining good bone health. Regular weight-bearing physical activity is a good place to start to strengthen our bones. Adequate intake of calcium and vitamin D, either in our diets or as dietary supplements, is important "fuel" for our bones. Also, several prescription medicines are available that can slow the development of osteoporosis and even reverse it.
Your healthcare provider can help you assess your risk for low bone mass. He or she may recommend measurement of your bone density with an X-ray specifically designed for this purpose, called bone densitometry or a "DEXA" scan (dual-energy X-ray absorptiometry scan). Persons at risk for osteoporosis (especially -- but not only -- thin women following menopause) are typically screened with bone density X-rays approximately every two years. Remember: good breathing and good bone health are both achievable.