Bone density and muscle mass are two critical components of overall health, particularly as we age. Low bone density can lead to fractures and osteoporosis, while low muscle mass can contribute to a range of problems, including falls, decreased mobility, lower quality of life and an increased risk of early death. While there are many ways to measure these factors, one increasingly popular method is the use of Dual-Energy X-ray Absorptiometry (DEXA) scans. DEXA scans are a non-invasive and accurate way to measure bone density and muscle mass, providing valuable information that can inform treatment plans and help individuals take a proactive approach to their health. In this article, we will explore the use of DEXA scans as an objective measure of bone density and muscle mass in research and how this is helpful in the assessment of osteosarcopenia and frailty.
My initial interest in the DEXA scan was prompted by my mother's second accidental fracture at the age of 55 (her first was a fibular fracture at age 51. The second fracture was a left proximal humeral fracture (upper arm) from a low-energy fall or also known as a frailty fracture (defined as a fracture from a standing height), when she tripped over and her outstretched arm hit the side of a desk that broke her fall. This type of fracture is indicative of underlying osteoporosis and her subsequent DEXA scan confirmed this. In addition, she also had low vitamin D levels despite a 'healthy' diet and a 'healthy lifestyle'.
The second reason for my interest was in finding an objective way of assessing my muscle mass since low muscle mass is also a risk factor for osteoporosis. In addition to muscle strength, many of these markers are highly correlated to frailty.
Fracture risk, frailty and mortality
The average age of fragility fractures is 63 for both men and women. The top 5 commonest fractures seen above age 50 are femoral, pelvic, spine, humerus and distal radius. 3 out of 5 are more common in women. (distal radius, proximal femur and proximal humerus). Having low bone mass or osteoporosis is a risk factor for fragility fractures.
There are several risk factors for osteoporosis, some of which, such as being female and having a direct relative with osteoporosis cannot be changed but there are others:
inadequate amounts of dietary calcium
low vitamin D levels
cigarette smoking
alcohol intake of more than two standard drinks per day
caffeine intake of more than three cups of coffee or equivalent per day
lack of physical activity
early menopause (before the age of 45)
loss of menstrual period if it is associated with reduced production of oestrogen, which is vital for healthy bones (the menstrual cycle can cease following excessive dieting and exercise)
long-term use of medication such as corticosteroids for rheumatoid arthritis, asthma and other conditions.
Some conditions may also place an individual at higher risk:
thyroid disease or an overactive thyroid gland
rheumatoid arthritis
chronic liver and kidney disease
conditions that affect the body’s ability to absorb nutrients, such as Crohn’s disease, coeliac disease and other inflammatory bowel conditions.
As a result of this increased risk from my family history, I was acutely aware of my risk for osteoporosis and sought to better understand what I needed to do to prevent this from happening to me. As I believed that osteoporosis and low muscle mass and strength are preventable through specific lifestyle changes. And as my research revealed to me, has an impact on future health risks, quality of life and mortality.
In 2009, a study showed an increased mortality risk within 5 years in men and women after a frailty fracture. This increased risk of death after a fracture was more likely in those with low bone density, weak quadriceps, physically inactive, and poor balance.
The World Health Organization defines osteopenia and osteoporosis as a T score equal to or less than −1 and −2.5 standard deviations, respectively, below the peak bone mass of a young healthy cohort. This is diagnosed based on a DEXA scan to assess bone mineral density (BMD).
Sarcopenia is a condition where there is a loss of muscle mass and function often associated with ageing. Evidence links poor muscle function, particularly weak grip strength, to increased all-cause mortality rates in middle-aged and older people. A frailty phenotype: low grip strength, gait speed and muscle mass overlap with sarcopenia leading to a multi-system impairment that is associated with an increased vulnerability to stressors. Having sarcopenia increases the risk of osteoporosis by 12.9 times and osteoporosis also increases the risk of sarcopenia, illustrating a bidirectional relationship between the two conditions.
Osteosarcopenia is defined as the presence of osteopenia/osteoporosis and sarcopenia. This condition affects 5-37% of those aged 65 and above and is found in 46% of those with frailty fractures.
Both bone density and muscle loss start to decline with age. This begins in the mid-30s with an accelerated decline in women around menopause. Similarly, muscle mass loss occurs from age 30 by 3-8% per decade with a higher rate of decline after age 60. This is something that can be measured and I also recommend tracking over time, especially if you have a higher risk. This is what I have been doing for the last 8 years since my 30s.
A Whole Body DEXA scan is the most commonly used tool in research and clinical practice to accurately determine BMD, and estimate lean body mass and muscle mass. It is considered a ’gold-standard’ measurement since studies show a correlation between health and future disease and death risk. Other measurements such as ultrasound for bone density are less accurate with a high variation of results between tests and are not reliable for diagnosis or assessment of ongoing treatment.
Another method known as the bio-impedance analysis or BIA can measure bone mineral content but again is not a gold-standard for diagnosis and treatment response. It also measures muscle mass and could be a useful way to track muscle using validated equations against DEXA.
A DEXA scan will measure the musculature of the arms and legs, known as appendicular lean mass (ALM), which accounts for ≥75% of skeletal muscle in the body and is required for good physical function. Older adults lose approximately 0.1 kg (0.5%) of ALM annually after the age of 40–50 years. The progressive loss of ALM may be a key element in the development and progression of frailty. Higher ALM was associated with a lower risk of mortality with each standard deviation increase in ALM being associated with a 50% lower risk of mortality.
A DEXA scan is non-invasive, usually takes around 30 minutes to complete and has low radiation exposure of 1-4 uSv (an average person is exposed to 8uSv from background radiation). Screening for osteoporosis is recommended at age 65 and above and at a younger age if there are additional risk factors such as those listed above.
In addition, grip strength is a non-invasive method for assessing muscle strength and in combination with a Whole Body DEXA, is a key component of my healthy longevity program. Instead of waiting to be screened at age 65 (since decline starts from mid-30s), I would recommend at least having one baseline at age 30-35 to assess if your lifestyle can prevent accelerated decline and whether the type of resistance exercise you are doing is effective at prevention. Knowing where you are compared to your peers and compared to a younger cohort is helpful and the goal is to avoid being in the bottom 25th percentile where the risk of all causes of death is the highest.
This is where lifestyle prevention is different to waiting until you have the condition and treating it.
But even if you already have osteoporosis or sarcopenia it is not too late to adopt lifestyle strategies in combination with medical treatment (if needed).
Lifestyle Treatment of Osteosarcopenia:
Ensure adequate vitamin D (1000iu per day) and calcium intake (500-600mg/day)
Protein intake of 1.2g/kg/day
Creatine 3-5g/day
avoid smoking
limit alcohol consumption
limit caffeine
Resistance exercises 2-3 times per week
Balance exercise 2-3 times per week
With the help of my knowledgeable exercise physiologist, I was able to understand that my current DEXA results place me at a positive T and Z score which indicates I have a higher bone density than a younger age cohort (T Score) and also for my age (Z score). My muscle mass is also in the top 65th percentile indicating a higher muscle mass than the average for my age. My grip strength is also above normal for my age and gender.
Research shows that individuals who continue to stay active and maintain the intensity of resistance training can reduce their loss of strength and bone mass with age.
I am less than 5 years from when my mum had her first fracture, and given the results and commitment to my fitness, I feel confident that osteosarcopenia and frailty is a condition that is less likely to become an issue in my older age. While there are no guarantees, health is about managing risks, and I believe even with a family history, there are choices and priorities that we can make and do our best to hedge against those risks.
This is a paradigm shift in health care, where you can be proactive about your health and learn ways in which you can optimise your own long-term quality of life and disease risks. Knowing where to start can be challenging. But going forward, our healthy longevity program is something you can consider joining to give you a head start, and this is the area on which we place our focus. Whether you already have osteoporosis, or osteopenia or want to know if you have low muscle mass, it is never too late to have a strategy personalised to you.
My mum was 72 when she started her first resistance training program, under the guidance of a credentialed fitness professional in conjunction with medical therapy for osteoporosis. I look forward to sharing her journey in the near future at her next DEXA Scan and strength assessment.
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References:
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https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/osteoporosis
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