Osteoporosis

Osteoporosis is a chronic skeletal condition characterised by reduced bone mass and deterioration of bone microarchitecture, resulting in increased bone fragility and a heightened risk of fractures. It is the leading cause of fractures among older adults and is particularly prevalent in postmenopausal women, though it affects both sexes across all populations. Bones commonly affected include the vertebrae, wrist, forearm, and hip. Because the disease progresses silently, it often remains undetected until a fracture occurs, sometimes following only minimal trauma or routine daily activities.

Characteristics and clinical features

Osteoporosis is defined by a significant reduction in bone density, typically measured using dual-energy X-ray absorptiometry. A bone density score of 2.5 standard deviations below that of a healthy young adult indicates osteoporosis. As bone becomes more porous and structurally compromised, susceptibility to fractures increases. Vertebral compression fractures are among the most characteristic signs and may present with sudden back pain, radicular symptoms, or, in severe instances, spinal cord compromise. Repeated vertebral fractures can lead to height loss, kyphosis, and chronic pain, contributing to reduced mobility and quality of life.
Fractures of long bones such as the femur often result in acute loss of mobility and usually require surgical intervention. Hip fractures are particularly serious; they are associated with a significant risk of complications including thromboembolism and carry a notable post-fracture mortality rate. In elderly populations, even minor falls can cause skeletal injury due to compromised bone strength. Recognised fracture risk calculators, such as FRAX, QFracture, and the Garvan tool, integrate clinical factors to estimate an individual’s likelihood of sustaining a fragility fracture.

Causes and underlying mechanisms

Osteoporosis may result from inadequate peak bone mass achieved during early adulthood or from excessive bone loss later in life. Bone loss accelerates significantly after menopause due to declining oestrogen levels, while a similar but less pronounced trend is observed in ageing men with reduced testosterone. Numerous medical conditions contribute to secondary osteoporosis, including hyperthyroidism, chronic kidney disease, anorexia nervosa, alcoholism, and endocrine disorders. Surgical removal of the ovaries can also induce rapid bone loss.
A variety of medications are known to increase bone loss. These include glucocorticoids, some antidepressants, proton pump inhibitors, chemotherapeutic agents, and certain anticonvulsants. Lifestyle factors such as insufficient physical activity, tobacco smoking, and excessive alcohol intake further exacerbate bone demineralisation. Smoking is believed to impair osteoblast function, reduce oestrogen activity, and lower body weight, all of which contribute to bone density reduction. Low vitamin D levels, common among the elderly, lead to increased parathyroid hormone secretion, stimulating bone resorption and accelerating loss of bone mineral content.

Risk factors

Risk factors for osteoporosis may be categorised as non-modifiable and modifiable.Non-modifiable factors include:

• Age: Bone mass naturally declines with advanced age.
• Sex: Women are at greater risk, particularly postmenopause.
• Ethnicity: People of European or Asian ancestry have a higher predisposition.
• Genetics: Family history of fractures or low bone density markedly increases risk.
• Body build: A smaller body frame is associated with lower peak bone mass.

Modifiable risk factors include:

• Alcohol consumption: Regular consumption exceeding three units per day significantly increases fracture risk.
• Smoking: Independently linked with accelerated bone loss and earlier menopause.
• Vitamin D deficiency: Leads to secondary hyperparathyroidism and bone demineralisation.
• Poor nutrition: Low intake of calcium, magnesium, and phosphorus impairs bone strength.
• Physical inactivity: Contributes to muscle loss and reduced mechanical stimulation of bone.

Osteoporosis is also recognised as an element of frailty syndrome in older adults. Factors that increase the likelihood of falls, such as impaired vision, balance disorders, neurological disease, medication-induced dizziness, and environmental hazards, further elevate fracture risk.

Epidemiology

The prevalence of osteoporosis increases sharply with age. Among people of Caucasian descent, approximately 15% in their fifties and up to 70% of those over eighty are affected. The condition is significantly more common in women, reflecting hormonal influences on bone metabolism. In developed regions, between 2–8% of men and 9–38% of women may meet diagnostic criteria, though figures vary according to measurement methods. Global statistics indicate substantial disease burden: tens of millions of adults in both Europe and the United States live with osteoporosis. Rates in developing countries remain less precisely defined, partly due to limited access to diagnostic imaging. White and Asian populations demonstrate the highest susceptibility.

Diagnosis

Diagnosis typically relies on dual-energy X-ray absorptiometry, which quantifies bone mineral density at vulnerable sites, most commonly the lumbar spine and hip. Results are reported as T-scores and compared with young adult reference values. A T-score of −2.5 or lower confirms osteoporosis, while milder reductions indicate osteopenia. Clinical evaluation also considers risk factors, fracture history, height loss, and symptoms such as back pain suggestive of vertebral collapse. Fracture risk calculators provide additional context for assessing treatment need.

Prevention and management

Preventing osteoporosis begins in childhood with adequate nutrition and weight-bearing physical activity, both of which are essential for achieving optimal peak bone mass. In later life, preventive measures include maintaining sufficient intake of calcium and vitamin D, engaging in regular exercise, and avoiding smoking and excessive alcohol. In postmenopausal women, hormone replacement therapy may slow bone loss, though its use must be balanced against potential risks.
Strategies to prevent fractures among individuals with osteoporosis include fall-prevention interventions such as home modifications, correction of vision problems, and management of balance disorders. Bisphosphonates are commonly prescribed to reduce fracture recurrence in those with a history of fragility fractures, though their benefit is less pronounced in individuals without previous fractures. They do not appear to influence overall mortality. Other therapeutic options may include calcium and vitamin D supplementation, selective oestrogen receptor modulators, and medications that inhibit bone resorption or promote bone formation.

Complications and impact

Beyond fractures, osteoporosis imposes a wide range of complications. Chronic pain, reduced mobility, deformity, and dependency frequently arise following significant skeletal injury, especially among older adults. Hip fractures carry particularly high morbidity and mortality, with considerable short-term risk of death due to postoperative complications. The broader societal impact includes diminished quality of life, prolonged rehabilitation needs, and substantial health-care expenditure.