A prior fragility fracture is arguably the single greatest risk factor for subsequent osteoporotic fractures, even more significant than a low bone mineral density (BMD) score alone. Having one fracture doubles the risk of experiencing another. However, pinpointing the absolute greatest risk depends on a comprehensive view of interconnected factors, including age, gender, and fall risk. The World Health Organization's Fracture Risk Assessment Tool (FRAX) combines these elements, demonstrating that while low BMD is critical, an older age and a history of fractures often carry more weight in the final risk calculation.
The Central Role of Previous Fractures
Research has repeatedly shown that a prior fracture is a powerful, independent predictor of future fractures. The increased risk is immediate and significant, with some studies showing the highest incidence of new fractures within the first year after the initial event. This occurs because a person who has already experienced a fragility fracture has a skeleton that is inherently weaker than bone mineral density tests may indicate. The initial fracture itself signals a fundamental compromise in bone quality and structural integrity that puts the patient on a dangerous trajectory toward further breaks.
Other Major Non-Modifiable Risk Factors
While previous fractures are highly predictive, other elements contribute significantly to overall risk. These factors cannot be changed, but understanding them is crucial for early detection and preventative care.
- Age: Fracture risk increases exponentially with advancing age, largely due to the cumulative effects of bone loss over time and age-related declines in muscle mass, balance, and vision. The risk of a hip fracture climbs tenfold between ages 65 and 90.
- Sex: Women are at a much higher risk of developing osteoporosis than men. The rapid drop in estrogen levels after menopause is a powerful accelerant of bone loss. For men, a gradual decline in testosterone after age 60 also increases risk.
- Race/Ethnicity: Caucasian and Asian individuals face a higher risk of osteoporosis and related fractures compared to people of other ethnicities. Genetics play a significant role in determining peak bone mass and rates of bone loss.
- Family History: A parental history of hip fracture is an independent risk factor for future fractures, suggesting a strong genetic component to bone strength.
- Body Frame Size: Individuals with a small, thin body frame have less bone mass to draw from as they age, putting them at greater risk.
The Critical Impact of Falls
Many osteoporotic fractures, particularly hip fractures, result from a fall. For an older adult with fragile bones, even a low-impact fall from a standing height can be devastating. Falls are incredibly common, with up to 40% of people over 70 falling at least once a year. The risk of an osteoporotic fracture is 27 times higher in those with both low bone density and a history of multiple falls compared to those without. Therefore, assessing and mitigating fall risk is a cornerstone of fracture prevention.
Fall Risk Factors
- Balance and Gait Issues: Impaired balance and unstable gait are primary contributors to falls.
- Medications: Certain medications, such as sedatives, antidepressants, and anticonvulsants, can impair balance and increase fall risk.
- Vision Problems: Poor vision can make it difficult to navigate uneven surfaces or spot obstacles.
- Environmental Hazards: A cluttered home, poor lighting, or loose rugs dramatically increase the risk of tripping.
Comparison of Major Risk Factors
| Risk Factor Category | Examples | Impact on Fracture Risk | Modifiable? |
|---|---|---|---|
| Prior Fractures | Previous fragility fracture of the hip, spine, or wrist. | The single strongest predictor of future fracture risk, doubling the likelihood. | No, but informs more aggressive treatment. |
| Non-Modifiable | Increasing Age, Female Sex, Caucasian/Asian Race, Family History, Small Body Frame. | Significant, with risk increasing exponentially with age. Estrogen loss in women is a key driver. | No, but awareness is key for prevention. |
| Bone Mineral Density (BMD) | T-score ≤ -2.5 (Osteoporosis), -2.5 < T-score ≤ -1.0 (Osteopenia). | A strong predictor, with each standard deviation decrease doubling risk. However, many fractures occur in those with osteopenia. | Modifiable with medication, diet, and exercise. |
| Falls | Balance issues, gait problems, certain medications, vision impairment. | The event that often triggers a fracture. Highly prevalent in older populations and increases risk dramatically, especially when combined with low BMD. | Highly modifiable through lifestyle changes and home safety. |
| Modifiable Lifestyle | Smoking, Excessive Alcohol, Low Calcium/Vitamin D Intake, Sedentary Lifestyle. | Substantially increases bone loss over time and can affect balance and muscle strength. | Yes, can be changed to reduce risk. |
Conclusion: A Multi-Pronged Approach to Prevention
While a prior fragility fracture holds the title of the greatest single risk factor, it is critical to recognize that a patient's overall risk is determined by a complex interplay of genetic, medical, and lifestyle factors. Low bone mineral density is a fundamental component, but age and the risk of falling act as powerful multipliers of that risk. Effective prevention strategies must therefore move beyond simply measuring BMD and address all contributing factors. This requires a comprehensive approach, including medical assessment using tools like FRAX, lifestyle adjustments, fall prevention, and—for high-risk individuals—appropriate pharmacologic therapy. By treating the patient and not just the BMD score, clinicians can provide more targeted and effective care to reduce the devastating impact of osteoporotic fractures. The Bone Health & Osteoporosis Foundation offers resources for those seeking to understand and manage their risk factors and improve their bone health.
