Overview of Osteoporosis Epidemiology

Stefan Parent, M.D., PhD, FRCSC
Montréal, QC

Osteoporosis is one of the most important diseases associated with aging. It is characterized by decreased amounts of bone with a normal architecture that results in an increased susceptibility to fractures. These insufficiency fractures are common, with close to 1.5 million people suffering from one osteoporotic fracture in the United States every year1. With the aging population, this condition is increasingly more prevalent. The annual incidence of vertebral osteoporotic fractures is 500 000 per year with one out of four Caucasian women experiencing a vertebral fracture in her lifetime2,3.

 

Risk factors for osteoporosis include biologic, genetic, behavioral and environmental factors. Caucasian race, fair skin and hair, Northern European heredity, scoliosis, early menopause and slender body build are all associated with an increased risk of osteoporosis. Cigarette smoking, alcoholism, inactivity, malnutrition, caffeine use, high-fiber diet and high-phosphate diet are behavioral and environmental factors associated with an increased risk of osteoporosis.

Peak bone mass is usually reached between 16 and 25 years old in most individuals. This is usually the greatest amount of bone in an individual's lifetime. After this peak, there is a gradual decrease in bone mass that eventually can result in osteopenia and osteoporosis. The peak bone mass is thus an important factor related to osteoporosis as the greater the maximal bone mass, the less likely one will develop osteoporosis. Men usually loose bone mass at a rate of 0.3% per year, whereas in women, this rate can be as high as 0.5%. This bone loss usually accelerates in the post-menopausal period with the trabecular bone of the spine loosing as much as 6% of bone mass per year in the years following menopause1. This accelerated bone loss phase, which usually occurs at the rate of 2-3% per year, can last between 6-10 years following menopause1. Women tend to be more affected by this rapid bone loss and osteoporosis is therefore much more common in females1. Riggs and Melton1 introduced the concept of fracture gradient of risk which determines the prevalence of fracture based on the bone density. At a bone density of 1 g/cm3 the prevalence of fractures is 32% and at less than 0.8 g/cm3 it is 50%.

The incidence of vertebral fractures in Caucasian women and men is difficult to precisely assess. Many fractures will never be diagnosed. Results from a large cohort of patients diagnosed with vertebral fractures showed a rapid increase in vertebral fracture incidence with increasing age with an incidence of 0.2 per 1000 under the age of 45 to an annual rate of 1.3 per 1000 for men and 1.2 per 1000 for women over the age of 854. The lifetime risk of developing a vertebral fracture is 16% for Caucasian women and 5% for Caucasian men5.

Although the exact incidence and prevalence remains unknown and is closely related to the definition used to determine what represents an insufficiency fracture of the spine, the societal impact of this health problem is significant. Policy makers should be concerned by the cost associated with this condition especially in the context of a rapidly aging population.

References

 

  1. Riggs, B.L. & Melton, L.J. The prevention and treatment of osteoporosis. The New England journal of medicine 327, 620-627 (1992).
  2. Riggs, B.L. & Melton, L.J. Evidence for two distinct syndromes of involutional osteoporosis. The American journal of medicine 75, 899-901 (1983).
  3. Melton, L.J. et al. Prevalence and incidence of vertebral deformities. Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA 3, 113-119 (1993).
  4. Cooper, C., Atkinson, E.J., O'Fallon, W.M. & Melton, L.J. Incidence of clinically diagnosed vertebral fractures: a population-based study in Rochester, Minnesota, 1985-1989. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research 7, 221-227 (1992).
  5. Melton, L.J., Chrischilles, E.A., Cooper, C., Lane, A.W. & Riggs, B.L. Perspective. How many women have osteoporosis? Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research 7, 1005-1010 (1992).

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