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Bone mineral density screening may be a billion-dollar industry, but only 15 percent of low-trauma fractures (meaning from a fall no more than from standing height) are due to osteoporosis in older women. Only 15 percent of fractures are due to having low bone density. Between the ages of 60 and 80, hip fracture risk increases 13-fold in men and women, whereas the age-related decline in bone mineral density accounted for only a twofold increased risk. So, the contribution of declining bone density to the exponential increase in hip fracture risk with age is relatively small. The vast majority of our age-related rise in hip fracture risk appears to have nothing to do with the measured density of our bones.
So, what’s the main contributor? Fall risk. Without a fall, even fragile hips don’t fracture. Falls are the primary cause of fractures—including vertebral fractures. The disparity between men and women in hip fracture rates is primarily not because men have stronger bones, but because women fall more often. Doctors just asking the simple question, “Do you have impaired balance?” can predict about 40 percent of all hip fractures––more than a bone scan diagnosis of osteoporosis. Even a weak osteoporotic bone is strong enough to survive normal life activities without the excessive loading that comes from a fall impact or, in the case of the spine, bending with your back to lift something rather than your knees.
The primacy of falls in fracture risk explains a number of apparent osteoporosis paradoxes. For example, despite the fact that about 75 percent of your bone mass may be determined by your genes, the heritability of bone fractures appears negligible at older ages (because the propensity to fall is much less inherited).
It also explains the poor predictive value of bone density screening for fractures. Adding bone mineral density measures to a hip fracture risk score based just on age, sex, height, weight, the use of a walking aid, and cigarette smoking status did little to improve its predictive power. A provocative editorial published in the Journal of Internal Medicine entitled “Osteoporosis: The Emperor Has No Clothes” suggested that it would be safer and more effective to focus on fall prevention rather than pharmaceutical intervention.
Even though only about 5 percent of falls result in a fracture, falls are very common amongst the aged, due in part to age-related muscle weakness and loss of balance. More than a third of those aged 65 or older fall each year. After a hip fracture, fewer than 50 percent regain their pre-fracture function in terms of walking ability and independence. What can we do to prevent injurious falls? Based on dozens of randomized controlled trials, the single intervention most strongly associated with a reduction in fall rates: exercise.
So, exercise doesn’t just boost bone density. More importantly, it also reduces the number of falls over time by 23 percent, and the number of fallers by 15 percent. So, if you followed 1,000 people around age 75 for a year, and 480 fell a total of 850 times without exercise, adding exercise would be expected to result in 72 fewer fallers and 195 fewer falls.
Tai Chi appears to reduce falls by 19 percent, balance and functional exercises (like sit to stand) may reduce falls by 24 percent, and multiple exercises—typically balance and functional exercise plus strength training—may reduce falls by 34 percent.
The reduced falls rate then translates into fewer fractures. A recent meta-analysis found that exercise interventions—mostly using a combination of resistance exercise to improve lower limb muscle strength and balance training—cut fracture rates nearly in half. One year-long trial that combined strength training with step and jumping aerobics, and focused on balance and agility, resulted in 74 percent fewer fractures over the five-year period after the study ended. Furthermore, more than 70 percent of the women in the combo exercise group went those five years without a single injurious fall––compared to less than half of those in the control group.
Trials on hip protectors, which cushion a sideways fall on the hip with plastic shields or foam pads sewn into special underwear, are often plagued with poor compliance. Studies have not found them to be useful for reducing hip fracture rates among those living at home, but trials in nursing homes or residential care facilities do show a small reduction in risk––translating into about 11 fewer people out of a thousand suffering hip fractures due to wearing hip protection.
There are also common-sense measures one can employ. Quality improvement trials involving interventions like patient education have shown a 10 percent reduction in fall rates. For example, keep things within reach so you don’t need to use step stools. Use non-slip mats in the bath and shower. Add grab bars in the bathroom. Keep floors clutter free. Remove small throw rugs, or use double-sided tape to keep them from slipping. And make sure all staircases have handrails and adequate lighting. You could also avoid taking walks during inclement weather, and for those who walk leashed dogs, consider choosing smaller breeds, or ensuring proper training to prevent them from lunging. Otherwise, the main ways to prevent fractures may not have changed much over the decades since the classic paper entitled “Strategies for Prevention of Osteoporosis and Hip Fracture.” The main ways to prevent these fractures are to “stop smoking, be active and eat well.”
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