What is your skeletal age? And how is the state of your bones likely to affect your chances of a premature death? Those are questions scientists at the University of Technology Sydney think an ageing population needs to consider.
In a study of more than 1.6 million adults, they found a bone fracture is associated with a loss of one to seven years of life, depending on gender, age and fracture site. The risk is greatest for patients with a hip fracture, about a third of whom die within a year. On the basis of this and previous research, they are proposing the idea of skeletal age as a metric for assessing risk.
Project leader Tuan Nguyen, a professor of predictive medicine, says in cardiovascular medicine one way of understanding someone’s chance of having a heart attack or stroke is to measure their heart age. Similarly in respiratory medicine, lung age can be used as a tool to urge smokers to quit. So it made sense to apply the same approach to the bones.
“Various studies have shown fractures are associated with an increased risk of premature death, yet doctors don’t normally talk to their patients about that,” says Nguyen.
“It can mean people don’t take bone health seriously enough. They aren’t getting treatment or taking preventive measures, which puts them at risk of further fractures and mortality. We thought we should develop a tool to inform people about their risk.”
That tool, the Bonecheck calculator, is available free online at bonecheck.org and is intended for people aged 50 and above. The algorithm was developed by Nguyen’s team using data collected from five sources, including the Dubbo Osteoporosis Epidemiology Study.
They evaluated 50 potential risk factors, identifying five that were most significant and measurable: age, bone-mineral density, body weight, number of fractures occurring after age 50 and number of falls in the past 12 months. Ideally, users will have had a DEXA scan – a low dose X-ray to measure bone density.
“We aim to empower individuals to take preventive action,” says Nguyen.
“The tool is also designed for doctors so they have evidence-based information they can discuss with the patient and come up with a treatment plan.”
Bones might seem solid but they are in a constant state of flux. Cells called osteoclasts break down the bone’s matrix of collagen and minerals, releasing calcium into the bloodstream for reuse in other parts of the body. And another set of cells, osteoblasts, balance this out by forming new bone.
For the first 20 years of life, the body builds new bone more quickly than old bone is removed. By age 25, most of us have reached peak bone mass. Then, later in life, the process is reversed as bone is broken down more quickly than it is formed.
Osteoporosis isn’t inevitable but a number of factors increase our chance of developing it, such as a poor diet, a sedentary lifestyle, smoking, alcohol, excessive caffeine, medications such as steroids, family history and being underweight.
Age and gender are the two most important factors. Women lose bone as oestrogen levels start to dip in the menopause transition, and they tend to have smaller, thinner bones in the first place. Half of women will have a fracture between menopause and the time they die. Men have a lower risk of fracture, but once they have had one they are more likely to die.
A class of drugs called bisphosphonates can be prescribed to improve bone density, and for women, there is evidence that hormone replacement therapy (HRT) slows bone loss and prevents fractures.
Lifestyle also makes a difference. Getting adequate calcium, vitamin D and protein and staying active – ideally a mix of weight training and high-impact jumping and hopping, along with balance exercises to reduce risk of falling – all help keep bones stronger for longer.
“It’s never too early to think about your bone health,” says Nguyen. “Don’t wait until a fracture has occurred to take preventative action.
“If your skeletal age is higher than your actual age, you should seek advice from your doctor on how to manage the higher risk.”
