Osteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density (BMD) is reduced, bone microarchitecture is disrupted, and the amount and variety of proteins in bone is altered. Osteoporosis is defined by the World Health Organization (WHO) in women as a bone mineral density 2.5 standard deviations below peak bone mass (20-year-old healthy female average) as measured by DXA; the term ‘established osteoporosis’ includes the presence of a fragility fracture.
Causes
Bone is continually remodeled throughout life because bones sustain recurring microtrauma. Bone remodeling occurs at discrete sites within the skeleton and proceeds in an orderly fashion. Bone resorption is always followed by bone formation, a phenomenon referred to as coupling. In osteoporosis, this coupling mechanism is thought to be unable to keep up with the constant microtrauma to trabecular bone. In adults, approximately 25% of trabecular bone is resorbed and replaced every year, compared with only 3% of cortical bone.
Osteoporosis is most common in women after menopause, when it is called postmenopausal osteoporosis, but may also develop in men, and may occur in anyone in the presence of particular hormonal disorders and other chronic diseases or as a result of medications.
Osteoporosis tends to run in families and is often called the ‘silent disease’ because bone is lost with no obvious signs. A person may not know they have osteoporosis until a strain, bump, or fall causes a bone to break.
Osteoporotic fractures are those that occur in situations where healthy people would not normally break a bone; they are therefore regarded as fragility fractures. Typical fragility fractures occur in the vertebral column, rib, hip and wrist.
Prevalence and Cost
- Osteoporosis affects an estimated 75 million people in Europe, USA and Japan.
- For the year 2000, there were an estimated 9 million new osteoporotic fractures, of which 1.6 million were at the hip, 1.7 million were at the forearm and 1.4 million were clinical vertebral fractures. Europe and the Americas accounted for 51% of all these fractures, while most of the remainder occurred in the Western Pacific region and Southeast Asia.
- 1 in 3 women over 50 will experience osteoporotic fractures, as will 1 in 5 men.
- Nearly 75% of hip, spine and distal forearm fractures occur among patients 65 years old or over.
- 10% loss of bone mass in the vertebrae can double the risk of vertebral fractures, and similarly, a 10% loss of bone mass in the hip can result in a 2.5 times greater risk of hip fracture.
- By 2050, the worldwide incidence of hip fracture in men is projected to increase by 310% and 240% in women.
- The combined lifetime risk for hip, forearm and vertebral fractures coming to clinical attention is around 40%, equivalent to the risk for cardiovascular disease.
- Osteoporosis takes a huge personal and economic toll. In Europe, the disability due to osteoporosis is greater than that caused by cancers (with the exception of lung cancer) and is comparable or greater than that lost to a variety of chronic noncommunicable diseases, such as rheumatoid arthritis, asthma and high blood pressure related heart disease.
