What is Osteopenia?
Osteopenia is a condition of reduced bone mineral density (BMD) defined by the World Health Organization as a T-score between -1.0 and -2.5 standard deviations below the mean of young healthy adults, representing bone density that is lower than normal but not as severe as osteoporosis. 1, 2, 3
Diagnostic Criteria and Measurement
T-scores are calculated by comparing a patient's BMD to the peak bone mass of young healthy adults (specifically, White females aged 20-29 years from the NHANES III database). 1
Dual-energy X-ray absorptiometry (DXA) of the lumbar spine and hip is the gold standard for diagnosis, measuring BMD at the femoral neck, total hip, and lumbar spine (L1-L4). 1, 2, 3
For patients younger than 50 years, Z-scores (comparing to age-matched populations) are preferred instead of T-scores, with a Z-score ≤ -2.0 considered abnormal. 1, 2
Plain radiographs have poor sensitivity for detecting osteopenia, requiring 30-40% bone loss before becoming radiographically apparent, so radiographic evidence should prompt formal DXA evaluation. 2
Clinical Significance and Fracture Risk
The critical clinical reality is that most fragility fractures in the population occur in people with osteopenia, not osteoporosis, because osteopenia is far more prevalent. 4, 5
Over 60% of White women older than 64 years have osteopenia, making it the most common bone density category in postmenopausal women. 4
In population studies, 56.5% of all fractures occurred in women with osteopenia, compared to only 26.9% in women with osteoporosis. 5
Fracture risk approximately doubles for each standard deviation decrease in BMD below the young normal mean. 2
Women with osteopenia plus a prior fracture have the same or greater fracture risk as women with osteoporosis alone, demonstrating that T-score is only one component of fracture risk assessment. 5
Risk Stratification Within the Osteopenic Range
Osteopenia represents a wide spectrum of fracture risk, and the diagnosis alone is neither an indication for treatment nor for reassurance. 4
Fracture risk varies substantially within the osteopenic range depending on the specific T-score value (e.g., T-score -2.4 carries much higher risk than -1.1), age, prior fracture history, and other clinical risk factors. 4
Women with T-scores below -1.5 have particularly high risk for vertebral and hip fractures, supporting consideration of therapy at this threshold in appropriate patients. 3
BMD should be incorporated into quantitative fracture risk calculations (such as FRAX) rather than used as the sole determinant of management. 2, 4
Treatment Considerations
For women aged 65 or older with osteopenia near the osteoporosis threshold (T-score approaching -2.5), treatment with bisphosphonates can cost-effectively reduce fracture risk. 1, 4
Post hoc analysis of risedronate trials showed 73% fracture reduction in women with advanced osteopenia (T-score between -2.0 and -2.5) and no prevalent vertebral fractures. 1
Treatment decisions should be based on overall fracture risk assessment using tools like FRAX, not T-score alone, incorporating patient preferences, fracture risk profile, and the balance of benefits, harms, and costs. 1, 2, 3
Major osteoporotic fracture risks of 10-15% over 10 years could be acceptable indications for treatment with generic bisphosphonates in motivated patients older than 65 years. 4
Common Pitfalls
Do not assume osteopenia is benign or requires no action—the majority of the population fracture burden originates from this group due to their large numbers. 4, 5
Do not treat based solely on T-score—incorporate age, prior fractures, body weight, smoking status, corticosteroid use, and other risk factors into a comprehensive risk assessment. 1, 6, 4
Do not rely on plain radiographs to exclude osteopenia—significant bone loss can be present before becoming radiographically apparent. 2