Bone density is a surrogate for fracture risk, write Jarrod McMaugh and Carlene McMaugh

Pharmacists are well versed in the nature of bone density and how it affects the risks of a fracture during a fall. What is less understood is that bone density doesn’t directly affect fracture rates, while falls risk does.

Bone strength is a surrogate endpoint that we measure and treat with medications and interventions in the hope that an individual is less likely to fracture during a fall, yet if we can address falls risk, the rate of low-trauma fractures is lowered.

What are “Surrogates”?

The term surrogate is used in therapeutics to describe an outcome (surrogate endpoint) or measurable characteristic of a person’s health (surrogate marker) that we can directly influence, that has an impact on the condition or symptom that we are hoping to improve.

An example of this is blood sugar levels or HbA1c – we can measure these figures for a person with diabetes, and we can implement interventions that will consistently change these figures, yet these figures are not ‘diabetes’ – they are surrogate markers that help us measure and track progress, and we know how these figures correlate with risk of complications.

For bone health, bone density is a surrogate for fracture risk. We know that osteopoenia is associated with a greater risk of developing osteoporosis…. we know that osteoporosis is associated with a greater risk of fracture during a fall, and for stature-altering bone degeneration (ie vertebral fractures).

What we don’t always take in to account is that a person with relatively good bone density may still fracture during a fall, while someone with osteoporosis may never experience a traumatic fracture (if they never fall).

This means that bone health requires us to look further than bone density, and look at falls risk as an integral part of overall bone health. Louis Roller’s article on Osteoporosis from last year provides an excellent overview of bone mineral density and factors that influence the development of osteoporosis.

Balance and muscle strength

Falls risk is altered significantly by the nature and quality of a person’s muscles.

As we age, bone density decreases, and muscle density changes right along with it. This results in a person who has poorer balance, less capacity to react quickly to a fall, and less body mass to cushion a fall on to their hip. This reduction in muscle strength is known as sarcopoenia.

Sarcopoenia is similar to osteopoenia in that the condition describes a reduction in strength and density of the affected tissue type, but muscles have the benefit of being reactive to change in a positive direction (ie we can build strength and density), while it is difficult to improve bone density over time.

Happily, interventions that we use to improve muscle strength and density can also impact on bone density by slowing bone mineral loss through trabecular remodelling.

Exercise that focuses on muscle tone and rhythmic movements has the greatest impact on bone strength and protecting against falls; dancing is a low-impact version due to twisting and rotational movements, while brisk walking or jogging is also very effective but may not be appropriate for those who already have a high fracture or fall risk.

For people who have low muscle density and established osteoporosis, isometric exercise is a method of improving muscle strength without increasing falls risk. Isometric exercise reduces impact on joints, and can be performed while sitting or in other stable stances that don’t cause a loss of balance.

Weight

A person’s weight can have a complex relationship with the risk of falls and fracture. Ideally, a person who is fit and within the ideal weight range will have a good bone density and muscle tone.

The reason weight becomes complex with falls risk is that a person who is overweight is likely to have poor muscle tone (therefore risk of falls is increased), but the excess weight can actually be protective of some fractures such as hip fractures.

In all but a few situations, reducing excess weight and gaining muscle tone is the best advice to provide to people who need to lose weight, but for people who already have a high risk of falls and/or fracture, reducing weight should not be a priority until other risk factors for falls are addressed.

Medications

Medications are a significant risk factor for falls. Not only can medications directly contribute to falls through impacts on drowsiness (Label 1), there are impacts on dexterity that will also contribute to falls risk (Label 1 and 12). Pharmacists needs to spend a significant amount of time discussing falls risk with patients who are using medications that require these labels, at the time of first supply, and regularly on refill.

Side effects of medications or the conditions that they treat should also be on the minds of pharmacists when thinking about falls risk. Postural or spontaneous hypotension, hypoglycaemia, dehydration, confusion, delirium, vertigo, or changes in dexterity will increase the risks of trips and falls. These issues should be part of the discussion pharmacists have with people who are at risk of fracture.

Summary

Bone health is more than the quality of a person’s bones. Keep in mind other risk factors such as muscle strength and tone, risk of falls, and risk of tripping due to medications and conditions, ensuring that both sides of the bone-health issue are addressed.

Jarrod McMaugh is a community pharmacy practitioner with Capital Chemist in the northern suburbs of Melbourne. He has extensive experience in developing and delivering professional services in the community pharmacy setting.

Carlene McMaugh has worked in the healthcare field for over 20 years in varied roles and as a pharmacist for ten years including three years working as a pharmacist in the UK. She currently works in Capital Chemist Coburg and in the pharmaceutical industry.