Osteoporosis and the Burden of Osteoporosis-Related Fractures
David W. Dempster, PhD
Scope of the Problem
Osteoporosis, a common bone disease that is characterized by loss of bone mass and structural deterioration of bone tissue, is a potential public health problem for approximately 44 million Americans.1,2 In the United States, 10 million individuals over the age of 50 years—8 million women and 2 million men—are estimated to already have the disease.1,3 In addition, approximately 34 million individuals have low bone mass (osteopenia), which places them at risk for developing osteoporosis or an osteoporosis-related fracture.2 As the population ages, these numbers are expected to increase to an estimated 14 million individuals with osteoporosis and more than 47 million cases of low bone mass by 2020.1
Abstract
Osteoporosis is responsible for approximately 2 million fractures annually, including hip, vertebral (spinal), wrist, and other fractures. Osteoporosisrelated fractures may lead to diminished quality of life, disability, and even death. In addition, the direct and indirect costs of osteoporosis and its associated fractures are tremendous. Given the aging population, by 2025, annual direct costs from osteoporosis are expected to reach approximately $25.3 billion. Thus, osteoporosis has significant physical, emotional, and financial consequences. With appropriate screening, healthcare providers can implement effective interventions before fractures occur and ultimately improve quality of life, as well as help curb looming osteoporosis-related costs.
( Am J Manag Care. 2011;17:S164-S169)
For author information and disclosures, see end of text.
The societal burden of osteoporosis includes direct medical costs, such as those associated with acute and rehabilitative care following osteoporosis-related fractures, as well as indirect costs related to poor health.4 Direct medical costs of osteoporosis in the United States were estimated to be between $13.7 billion and $20.3 billion in 2005.5 Also, it is projected that by 2025, there will be over 3 million fractures, with related expenditures of $25.3 billion per year.1,6 Fractures can result in wide-ranging healthcare resource utilization and costs beyond the direct costs attributable to acute fracture treatment and follow-up. For example, patients whose fractures are treated in inpatient facilities may require subsequent hospitalization for postoperative complications, such as chest infection, venous thromboembolism, or pneumonia.6 The high morbidity and consequent dependency associated with these fractures may strain interpersonal relationships and social roles of patients and their caregivers.
Potential Consequences of Osteoporosis
Osteoporosis can lead to numerous other clinical and healthrelated consequences, including fracture, the need for long-term care, and excess mortality. The reduced bone density associated with the disorder is a major risk factor for fracture, especially of the hip, spine, and wrist.2,3 Osteoporosis is often referred to as a silent disease, as many individuals do not realize that they have the disease until a fracture occurs.7 Each year, about 2 million individuals
experience an osteoporosis-related fracture, which in turn is associated with increased risk of both morbidity and mortality.7 The risk of fracture increases dramatically with age in both men and women, as a result of both increased fragility of bones and an increased risk of falling. Roughly 24% of women 50 years or older and 16% of men 50 years or older fall each year, and this rises to nearly 50% of women age 85 or older and 35% of men age 85 or older.3
Osteoporosis-related fractures impose a heavy burden on individuals and on society, as they often lead to a variety of physical and psychological consequences, including future fractures, depression, functional impairment, pain, and disability.8 Fractures, especially vertebral fractures, can be associated with chronic, disabling pain.9 In addition, fractures can be extremely debilitating. In particular, hip fractures result in a 10% to 20% increase in mortality risk within 1 year and are associated with a 2.5-fold increased risk for the development of future fractures.3,10 Nearly one-third of patients with hip fracture are admitted to a long-term care facility within a year following their fracture.9 Approximately 20% of hip fracture patients require long-term nursing home care, and the majority of patients do not regain their prefracture level of independence.3 Rehabilitation is lengthy and many individuals never regain their pre-fracture level of mobility, which can have a significant impact on lifestyle and well-being.11 For instance, decreased functionality often results in total or partial inability to fulfill social roles or a need to remain in long-term care facilities, which may lead to psychological issues such as depression or anxiety.
Osteoporosis is a preventable disease that can be diagnosed and managed before any fracture occurs. In patients who have already experienced a fracture, the appropriate use of available therapies can effectively decrease the risk of future fractures.3 Although osteoporosis is a common and preventable disease, the prevalence of the disease and the incidence of osteoporosis-related fractures continue to increase due to the aging population. As a result, cost estimates associated with osteoporosis will likely also continue to rise. Therefore, efforts to address the looming financial burden must focus on reducing the prevalence of osteoporosis and the incidence of costly fragility fractures.
Osteoporosis and Bone Health
Osteoporosis can be defined as a skeletal disorder that is characterized by compromised bone strength which leads to an increased risk of fracture.9 Whole bone strength, which is determined by the integration of bone density and bone quality, is the key to understanding fracture risk. The ability of bone to resist fracture depends on several factors including
n Table 1. Determinants of Bone Strength12-14
Bone mass
Bone quality
• Microarchitecture
• Microdamage
• Collagen traits • Mineralization
bone mass, the shape and microarchitecture of the bone, and innate properties of the materials that comprise the bone (eg, mineralization and microdamage) (table 1).12-15 Bone density measures grams of mineral per area or volume, and is determined by peak bone mass and amount of bone loss.9 Peak bone mass is achieved between the ages of 18 and 25 years, and is largely determined by genetic factors.4 Other determinants of peak bone mass include nutrition, endocrine status, physical activity, and overall health during growth.4
Bone quality is an amalgamation of all the factors that, in addition to bone mass, determine how well the skeleton can resist fracture, including microarchitecture, accumulated microscopic damage, the quality of collagen, the degree of mineralization, and the rate of bone turnover. Bone remodeling, specifically the balance between the formation of new bone and bone resorption (breakdown of bone), is the biologic process that maintains a healthy skeleton and mediates changes in the factors that influence bone strength. Remodeling does not change the shape of bone, but is vital for bone health as it repairs skeletal damage that can result from repeated stresses by mending small areas of damage. Remodeling also serves to renew the cellular elements of bone, in particular, the osteocytes, which are derived from osteoblasts. Osteocytes play a key role in bone health by regulating the remodeling process, among many other functions. In addition, remodeling prevents the accumulation of too much old bone, which can lose its resilience and become brittle. On a cellular level, bone remodeling involves osteoblasts (cells that form bone) and osteoclasts (cells that break down bone). When the balance between the formation of new bone and bone resorption is altered and there is greater bone breakdown than replacement, bone loss occurs. Thus diseases and pharmacologic agents that impact bone remodeling will ultimately influence bone’s resistance to fracture.
As discussed, the composition of the mineral and matrix, the fine structure of trabecular bone, the porosity of cortical bone, and the presence of microfractures and other forms of bone damage are all important determinants of bone strength. Alterations in the microarchitecture of trabecular bone are especially critical as osteoporosis-related fractures
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Reports n Figure. Normal Versus Osteoporotic Bone16
Normal Bone Osteoporotic Bone
most commonly occur at sites that are rich in trabecular bone, such as the spine, wrist, and hip. Normal trabecular bone structure consists of resilient interconnected plates and broad beams that provide great strength. In individuals with osteoporosis, these plates are disrupted and deteriorate into weakened rod-like structures that are no longer well connected (Figure).16 These disconnected rods of bone may lead to overestimation of bone strength by bone mineral density (BMD) assessment as they may be measured as bone mass, but fail to contribute to bone strength.
Assessment of the extent of compromised bone strength can help to predict the magnitude of fracture risk; however, there is currently no accurate measure of overall bone strength. BMD is frequently used as a proxy measure and accounts for approximately 70% of bone strength. According to the World health Organization (WhO), osteoporosis is defined as a T score of -2.5 or lower, while osteopenia or, more appropriately, “low bone density,” is defined as a T score that is higher than -2.5 but less than -1.0.17 Osteopenia indicates bone density that is lower than normal, yet not so low as to be defined as osteoporosis.
Low Bone Density (Osteopenia)
As with osteoporosis, low bone density (osteopenia) can be readily diagnosed using BMD. Low bone density, as a clinical condition, has been compared with
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