26th January 2024

Causes and risk factors

Osteoporosis manifests when there is inadequate peak bone mass and/or ongoing bone loss. Peak bone mass is achieved in early adulthood. It depends on genetics, sex hormone status, levels of physical activity and nutritional intake of calcium and vitamin D. The rate of bone loss is accelerated in women around the time of the menopause due to oestrogen deficiency, decreased testosterone in elderly men and hyperparathyroidism.

The risk of sustaining a fragility fracture is influenced by factors, including bone strength (determined by BMD), the individual patient’s risk of falls and the presence of certain risk factors. As the BMD decreases, the risk of fractures increases, but BMD alone cannot be used to predict fracture risk in the absence of consideration of other risk factors. The risk factors affecting bone strength can be subdivided into those that reduce BMD, those which do not reduce BMD and those with unestablished mechanisms as shown in the table below.

Table 4: Risk factors affecting bone strength

Adapted from Kumar and Clark’s Clinical Medicine. 2017 Kumar P, Clark ML. Kumar and Clark’s Clinical Medicine E-Book. Elsevier Health Sciences; 2012 Jun 4.

Falls are often multifactorial; however, some common risk factors are impaired vision, impaired gait, lower limb weakness, use of alcohol and drugs, and polypharmacy.