Osteoporosis is a disease characterised by low bone mass and microarchitectural deterioration of bone tissue, leading to bone fragility and increased fracture risk.¹ For information about preventing falls, see Falls.

Generally, osteoporosis is underdiagnosed. Because osteoporosis has no overt symptoms, it is often not diagnosed until a fracture occurs. It is therefore difficult to determine the true prevalence of the condition. Information about ‘diagnosed cases’ is likely to underestimate the actual prevalence of the condition. An estimated 924,000 Australians have osteoporosis, based on self-reported data from the Australian Bureau of Statistics (ABS) 2017–18 National Health Survey,² and 20% of people aged ≥75 years have osteoporosis.³ The definition of osteoporosis given above includes people who were told by a doctor or nurse that they had osteoporosis or osteopenia.³

Osteoporosis is more common in women than in men, with 29% of women aged ≥75 years having osteoporosis in 2017–18 compared with 10% of men.³ The proportion of women with osteoporosis increases with age, with those aged ≥75 years being most affected.

The goal of the prevention and treatment of osteoporosis is to reduce a person’s overall fracture risk, not just to maintain bone density. Approximately 70% of fragility fractures occur in women,⁴ and comprehensive treatment can halve (30–70%) the risk of subsequent fragility fracture.⁵ The absolute risk reduction and value of treatment is highest in those at highest risk (eg those with a previous fragility fracture), but the majority remain untreated in general practice and hospital settings.^6,7

Osteoporosis is diagnosed on the presence of a fragility fracture (a fracture from the equivalent of a fall from standing height or less, or a fracture that under normal circumstances would not be expected in a healthy young man or woman). For epidemiological and clinical purposes, osteoporosis is defined by bone mineral density (BMD) as a T-score of ≤–2.5. However, age, lifestyle factors, family history and some medications and diseases contribute to bone loss and an increased risk of fragility fractures. A presumptive diagnosis of osteoporosis can be made without BMD measurement if an individual has a fragility fracture not from another cause.

There have been three recent large population-based randomised control trials of screening in women for the prevention of osteoporotic fractures: Screening in the Community to Reduce Fractures in Older Women (SCOOP) in the UK,¹⁴ Risk-stratified Osteoporosis Strategy Evaluation (ROSE) in Denmark¹⁵ and SALT Osteoporosis Study (SOS) in the Netherlands.¹⁶ The optimal thresholds of absolute fracture risk and implementation strategies are inadequately defined for the Australian context and there are no data on screening for men. Accordingly, there is currently insufficient evidence to support a population-based osteoporosis screening program in Australia.

Two of the most widely validated methods to estimate absolute fracture risk for osteoporotic fractures relevant to the Australian population are the Garvan bone fracture risk calculator and the Fracture Risk Assessment tool (FRAX^®).These calculators can be used with and without BMD measurement, although the Garvan bone fracture risk calculator has not been validated in an external cohort when BMD has not been used in the calculator.¹⁷ Risk estimation is imperfect, with the tools being modest predictors of fracture risk.^18,19 Risk factors (eg falls, glucocorticoid use) not included in one or the other risk algorithm require clinical judgement to modify the risk estimate.

If BMD is indicated, then it should be measured by bone density (DXA) scanning performed on two sites, preferably anteroposterior spine and hip. Without bone-losing medical conditions (eg hypogonadism, antigonadal therapy or corticosteroid use), BMD is unlikely to change significantly in <2 years. The average decrease in T-score is usually approximately 0.1/year if there are no specific bone-losing medical conditions.

Although there appears to be little or no effect of increased protein in healthy adults, for institutionalised older adults a recent Australian study of the effectiveness of increasing calcium and protein intake (<1 g/kg body weight protein per day) by providing residents with additional milk, yoghurt and cheese showed a 11% reduction in the risk of falls, a 48% reduction in hip fractures and a 30% reduction in all fractures.¹⁰

There is insufficient evidence to recommend a different screening or treatment approach in Aboriginal and Torres Strait Islander peoples.