Epidemiology Distribution and Incidence

Osteoporosis was defined as a clinical entity by Fuller Albright and colleagues in 1941. Since that time a large number of epidemiological studies have been performed to evaluate the varying rates of osteoporosis and osteoporosis-related fractures in different populations. The process of age-related and postmenopausal bone loss occurs in all populations. It appears to start earlier for women in Japan and India as compared to women in Britain and the United States. It occurs later in Finnish women, and age-related rates of bone loss of women between 35 and 64 years of age are lower in Jamaica and the four African countries studied than in the other countries examined (Nordin 1966).

Relating the differing rates to calcium intake correlates well with the populations in Japan, India, and Finland but not Jamaica or the African countries. Other factors such as genetically determined initial bone density or increased physical activity may also be involved. The rate of hip fracture varies according to the age distribution of osteoporosis in all countries. This distribution involves a much broader age group in India secondary to the prevalence of rickets and osteomalacia.

Black females in both Puerto Rico and Michigan have less osteoporosis than do white females in Michigan. However, both groups demonstrate a very high prevalence with advanced age: 60 percent of those over 65 years in Puerto Rico and 80 percent over 65 years in Michigan (Smith and Rizek 1966). The incidence rates of hip fracture are higher in white populations in all geographic areas including Israel and Singapore, compared to the indigenous populations. A very low incidence rate is also noted among the Maoris of New Zealand and Bantu of South Africa compared to white populations in both areas. The age-adjusted incidence rate of hip fracture for females and males per 100,000 is 5.3 and 5.6 among the Bantu compared to 101.6 and 50.5 among blacks in the United States (Cummings et al. 1985).

In the United States, over 90 percent of all hip fractures occur in individuals over age 70 years. By age 90, a third of all women will have sustained a hip fracture. Vertebral fractures are present in 25 percent of women over age 70.

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