Epidemiology and pathogenesis of osteoporosis

Osteoporosis is likely to become the most common disorder of our aging population. An understanding of factors that affect the incidence of osteoporosis is critical if we are to successfully minimize the impact of this disorder on morbidity, mortality, and the cost of health care. This article will provide an overview of the frequency, distribution, and consequences of the various types of osteoporotic fractures in different populations. We will discuss the major risk factors, emphasizing those that are reversible. Fracture risk not only involves abnormalities of bone mass and architecture, but also factors that affect the incidence of falls. The racial, ethnic, and geographic differences in fracture incidence are associated with parallel differences in bone mineral density (BMD), but the differences are often relatively small, suggesting that other architectural or metabolic differences in the skeleton make an important contribution. On the other hand, when combined with low BMD, multiple risk factors and comorbid conditions increase the risk of fracture as well as morbidity and mortality from fracture. Osteoporosis can result pathogenetically from inadequate peak bone mass, excessive bone resorption, or impaired bone formation. These can be affected by genetics, nutrition, lifestyle, systemic hormones, and local factors. The relative importance of these mechanisms is not fully understood and may differ among patients. Nevertheless, our current understanding of epidemiology and pathogenesis can help clinicians to develop the optimal approach to diagnosis and management.