Do you suffer from low bone mass? If you are over the age of 50, you may be one of the 54 million US citizens who do. This is an issue, given that low bone mass can lead to an increased risk of fractures. And since fractures have been associated with a decreased quality of life and increased mortality, it is important to keep them to a minimum! There have been a few studies that have linked the incidence of fractures to the presence of obstructive sleep apnea (OSA), but how are these two related? Let’s review the evidence.
First, very importantly, OSA and fractures are both increased in the elderly population, since airway collapses become more likely and motor/cognitive abilities falter (possibly leading to an increase in falls). It may be, then, that these two factors simply co-exist without one causing the other. However, it is important to examine some potential mechanisms that could explain whether or not they are linked.
Interestingly, there is a sort of “bone cycle” that continually occurs. Proteins that help to build up and keep bones healthy, which are called bone turnover markers, are circulated within the bone location and also through the blood stream. By tracking blood markers, we are able to see how efficiently or inefficiently the bone cycle is occurring. It has been found in the past that bone turnover markers have a distinct day-night cycle, and it is possible that sleep disrupts this cycle. In this way, sleep apnea may negatively affect bone health by disrupting sleep. This evidence is supported by a study showing that those with insomnia (who suffer from short sleep time) also have an increased risk of osteoporosis.
In addition to sleep fragmentation, sleep apnea also induces hypoxia, which is lack of oxygen in the blood stream. As may be expected, hypoxia is very bad for the brain and the body. So is it bad for bones? In fact, yes, it seems that hypoxia, which can be simulated in a lab setting, induces acidosis and inflammation in the bone microenvironment. These factors can again disrupt the bone formation/upkeep cycle, or they could make bones more susceptible to injury.
Overall, it seems that both negative consequences associated with sleep apnea (sleep fragmentation/disruption and hypoxia) are both linked tightly to bone density. It seems that these two factors do not simply co-exist, and sleep apnea may indeed weaken bones. Treating sleep apnea, however, likely minimizes or reverses these effects. In the end, it is best to pick a treatment and stick to it. Also, walk carefully and try to keep your body strong to reduce the risk of injury in other ways!
Swanson, C. M., Shea, S. A., Stone, K. L., Cauley, J. A., Rosen, C. J., Redline, S., ... & Orwoll, E. S. (2015). Obstructive Sleep Apnea and Metabolic Bone Disease: Insights in to the Relationship Between Bone and Sleep. Journal of Bone and Mineral Research.