EPIDEMIOLOGY OF BONE LOSS WITH AGING

Bone is a highly metabolically active tissue with remodeling continuin g throughout life. This remodeling process involves a delicate balance between bone resorption by osteoclasts and bone formation by osteobla sts. In humans, the resorptive period takes approximately 30 days, and the bone-forming phase some 130 days. An imbalance in this active cou pling phenomenon in which more resorption than formation occurs leads to a net loss of bone per remodeling cycle. Age-related bone loss is a possible result of alterations in calcium absorption, vitamin D metab olism, vitamin D effects (resistance), osteoblastic and osteoclastic a ctivity, or a combination of these. The major consequence of bone loss in our aging society is fracture. The incidence of fracture increases dramatically as bone density deceases and the risk of falling increas es with age. Hip fracture, a less common but more devastating skeletal fracture associated with bone loss and aging, represents a major heal th problem in the elderly population with significant morbidity, morta lity, and expense.