Osteoporosis: Definition, Impact, and Clinical Significance
Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, leading to increased bone fragility and susceptibility to fracture. 1
Definition and Pathophysiology
- Osteoporosis is defined by the World Health Organization as a bone mineral density (BMD) that is 2.5 standard deviations or more below the young adult mean value (T-score less than -2.5) 1
- The condition results from an imbalance where osteoclastic bone resorption exceeds osteoblastic bone formation, causing progressive deterioration of bone structure 2
- Bone microarchitecture changes differ between sexes: men experience trabecular bone loss primarily through decreased trabecular thickness while maintaining connectivity, whereas women lose trabecular connectivity 1
Epidemiology and Public Health Impact
- Osteoporosis affects an estimated 10.2 million adults in the United States over age 50 1
- Approximately 50% of women and 30% of men over age 50 will sustain an osteoporotic fracture in their remaining lifetime 1
- The global burden is increasing, with fracture numbers projected to rise by 310% between 1990 and 2050 1
- Common fracture sites include vertebrae, hip, distal radius, and proximal humerus 1
Risk Factors
- Age is a primary risk factor (>70 years for men, postmenopausal status for women) 1
- Low body weight (BMI <20-25 kg/m²) and weight loss (>10% of usual weight) 1
- Physical inactivity and sedentary lifestyle 1, 3
- Use of oral corticosteroids 1
- Previous fragility fracture 1
- Additional risk factors include smoking, low calcium intake, excessive alcohol consumption, vitamin D deficiency, and androgen deprivation therapy in men 1, 3
Clinical Consequences
- Osteoporotic fractures cause significant morbidity, diminished physical function, and reduced independence 1
- Hip fractures are particularly serious, with 20% mortality rate and 50% resulting in permanent disability 4
- Men have higher mortality following fractures than women (37.5% vs 28.2% one-year mortality after hip fracture), likely due to greater comorbidities 1
- Most low-trauma vertebral fractures are clinically silent but still indicate skeletal fragility 1
Diagnosis
- Dual-energy X-ray absorptiometry (DXA) is the primary diagnostic tool, measuring BMD at the lumbar spine and femoral neck 1
- Screening is recommended for women >65 years and men >70 years 1
- Earlier screening is warranted in those with additional risk factors 1
- Osteopenia is defined as a T-score between -1 and -2.5 1
- Fracture risk increases 2-3 fold for each standard deviation decrease in BMD 1
Management Approaches
- Prevention strategies include adequate calcium and vitamin D intake, regular weight-bearing exercise, smoking cessation, and limiting alcohol consumption 3, 4
- Pharmacological treatments include:
- Bisphosphonates like alendronate work by inhibiting osteoclast activity, reducing bone turnover while allowing bone formation to exceed resorption 2
Important Clinical Considerations
- Most fragility fractures occur in patients with BMD T-scores higher than -2.5, highlighting the importance of evaluating overall fracture risk beyond BMD alone 1
- A fragility fracture in an adult is a strong predictor of future fractures and requires evaluation and treatment of underlying osteoporosis 1
- Vertebral fracture assessment and review of past imaging is crucial as many vertebral fractures are asymptomatic 1
- Treatment adherence is a significant challenge, with 30-50% of patients not taking medications correctly 3
Osteoporosis represents a major public health challenge with significant implications for mortality, morbidity, and quality of life. Early identification of at-risk individuals, appropriate screening, and timely intervention are essential to reduce fracture risk and associated complications.