OSTEOPOROSIS OVERVIEW

Osteoporosis is a devastating disease that is affecting millions of lives. The costs of osteoporosis are enormous, both to the individual who is afflicted with the disease and to society in general. It has been estimated by the National Osteoporosis Foundation (NOF) that in 1996 approximately 29 million people aged 50 and over in the United States either had osteoporosis or were at risk of developing the disease; this number is expected to rise to over 41 million by the year 2015 (1). Writing in the Journal of Bone and Mineral Research, Ray et al estimate the current costs to the health care system to be nearly $14 billion annually ($38 million each day) (2).

An age-related illness, osteoporosis is characterized by decreased bone tissue and increased susceptibility to fractures. It has been called the "silent disease" because its progression is so insidious; most individuals are not aware they have osteoporosis until they actually fracture a bone (usually the hip, spine, or wrist). Approximately 1.5 million fractures per year are osteoporosis related: 300,000 hip fractures, 700,000 vertebral fractures, 250,000 distal forearm fractures, and 250,000 fractures at other sites (1).

Because osteoporosis primarily affects our older citizens, it is of particular concern to health professionals in West Virginia. In 1996, West Virginia had the oldest population in the nation according to population estimates published by the U.S. Census Bureau (3). The state's median age was 37.7, higher even than that of Florida (37.6). Given the state's low birth rate, our population will continue to age. As this happens, the public health burden of osteoporosis in West Virginia will increase accordingly.

Statistics from the National Institutes of Health (NIH) reinforce the serious nature of osteoporosis (4). According to the NIH, one in every two women and one in eight men will suffer an osteoporosis-related fracture at some time in their lives. A woman's risk of a hip fracture is equal to her combined risk of having breast, uterine, or ovarian cancer. Sufferers of hip fractures have a 5% to 20% greater risk of dying within the first year after their injury compared to others in the same age group. One-half (50%) of persons who have a hip fracture will be unable to walk without assistance during their remaining lifetime; 25% will require long-term care. While the rate of hip fracture is higher among women than men, men are more likely to die during the year following their fracture.

Osteopenia and Osteoporosis

Bone is composed of protein (collagen) and minerals, primarily calcium salts and phosphate. The first stage of osteoporosis is a condition known as osteopenia, i.e., a decrease in the volume of mineralized bone. When osteopenia advances to the point where there is a reduction in total bone (protein and minerals), the disease stage of osteoporosis has been reached. Compared with normal bone, osteopenia carries a 2-fold increased risk of fracture, while osteoporosis carries a 4- to 5-fold increased risk of fracture (5).

Normal bone consists of two layers: cortical bone and trabecular bone. Cortical bone forms the outer layer and is dense and compact, while trabecular bone has a honeycomb structure and is much more porous. Cortical bone provides one-third of total skeletal surface and three-fourths of skeletal mass; trabecular bone, on the other hand, provides two-thirds of total skeletal surface but only one-fourth of skeletal mass. Most cortical bone is found in the shafts of the long bones of the appendicular skeleton (upper and lower limbs). Trabecular bone is found in axial skeletal bones (cranium, vertebrae, ribs, and sternum) and the ends of the long bones.

Bone is a living tissue that undergoes constant remodeling, or turnover, during its lifetime. Large cells called osteoclasts absorb bone tissue, leaving microscopic cavities. Other cells, known as osteoblasts, produce new bone to fill the cavities. Bone mass refers to the amount of mineralized tissue in the bone; the higher the bone mass, the stronger the bone. Bone mass is accumulated during childhood and young adulthood, reaching a peak between the ages of 25 and 35. (Trabecular bone forms earlier than cortical bone.) Peak bone mass is determined by such factors as genetics, diet, exercise, and an individual's overall health. Men have a higher bone mass than women, while African Americans have greater bone mass than white or Asian Americans. Adequate calcium and Vitamin D intake and regular physical activity during the skeleton's formative years can increase bone mass, while cigarette smoking and immoderate alcohol use can decrease mass.

After age 35, both men and women begin to lose bone mass (0.3% to 0.5% yearly) as a normal part of aging, through an imbalance of the remodeling process. During the years following menopause, a woman's bone loss, especially of trabecular bone, accelerates due to her decreased estrogen levels. It has been estimated that women can lose from 2% to 4% of their trabecular bone mass per year for five to ten years after menopause, adding up to 25% to 30% of their total trabecular bone. Because the spine is composed primarily of trabecular bone, often the first fractures that occur as a result of postmenopausal osteoporosis are compression fractures of the vertebrae. Compression fractures can be painless and thus undetected until there is a noticeable loss of height. Curvature of the spine, called kyphosis, can also occur, leading to chronic back pain. Spinal fractures distort the skeletal anatomy, causing reduction of the thoracic and abdominal cavities and in time affecting the functioning of the heart, lungs, stomach, and bladder. The postural disfigurement, reduced mobility, pain, and psychological distress that can accompany compression fractures have a profound effect on an individual's quality of life.

In senile (due to aging) osteoporosis, both cortical and trabecular bone are affected. Among the elderly, hip fractures are more common than spinal fractures, with a more even sex distribution. Weak, osteoporotic bone is slow to heal after surgical repair of the fracture and acute complications can follow, including pneumonia, pulmonary embolism, and depression. Aggressive physical therapy, often difficult for an elderly patient, may be necessary to overcome the consequences of prolonged bed rest. As a result, most patients fail to recover their full range of activity. While other fractures, such as that of the distal forearm bone, may be less traumatic, they still result in the loss of the use of the extremity for a certain period of time, limiting the individual's ability to function normally. All fractures promote a fear of additional falls and injuries and the loss of independent living.

Detetction

Risk Factors

Prevention and Treatment