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The potential effect on hip fracture incidence of mass screening for osteoporosis

Nicholas A Pocock, Nicole L Culton and Neil D Harris

MJA 1999; 170: 486-488
For editorial comment, see Morris et al; see also Sanders et al.

With ageing of the Australian population, treatment of osteoporosis-related hip fractures will impose an increasing burden on the healthcare system. Based on current age-adjusted hip fracture incidence and population projections for New South Wales, we estimated a 90% increase in hip fractures by the year 2021. Contributing significantly to this increase will be the number of men reaching the high risk age group for osteoporotic hip fractures. A suggested solution -- screening and appropriate therapy for individuals at high risk of osteoporosis -- may have only a modest impact. Our calculations show that, even with optimistic screening and therapy compliance rates, hip fractures could still increase by over 50%. Other approaches need to be further explored.

Introduction - Discussion - References - Authors' details
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Introduction Osteoporosis-related hip fractures are a high-cost item in the Australian healthcare budget, and place considerable demands upon the limited resources of the public health system. This burden will increase in the first quarter of the next century as the projected Australian population over 65 years of age increases from the current level of 2.25 million to between 4.02 and 4.05 million by 2021.1 To avoid this impending healthcare crisis, several reports have suggested a screening program to identify individuals at high risk of osteoporosis, followed by appropriate intervention to reduce the number of hip fractures.2-6

The possible introduction of a mass-screening program for osteoporosis raises a number of issues. Cost effectiveness is of major importance, and there are reports to indicate that screening for osteoporosis may well be cost effective.3,5,6 However, few data exist on the impact of a screening program on the healthcare system, and, in particular, on the demand for acute-care hospital beds, which has important implications for healthcare planning.

To assess the impact of screening on the demand for hospital beds for hip fracture treatment, we have used available population projections for New South Wales (NSW) to calculate the likely number of hip fractures in people aged 65 years or older by the year 2021. We then assessed the potential of a screening program, coupled with effective therapy, to reduce hip fracture incidence using available data on population capture rates of current large screening programs, and data on therapy compliance and drug-efficacy rates. Our methods and the results we obtained are shown in the Box.

Discussion Current costs of osteoporotic hip fractures in Australia exceed $400 million annually,15 and hip fracture treatment is making great demands on an already overstretched hospital infrastructure.2,7,16,17

In 1994-95, there were 52017 admissions to NSW hospitals of patients over 65 years of age with major hip fractures. Without further intervention, our calculations show that, even with a low population growth model, this figure may rise by the year 2021 to 9800 hip fracture admissions annually in this age group, an increase of about 89%. A major cause will be the increase in the number of men reaching the high risk age group for osteoporotic hip fractures. In 1997, the population of men in NSW over 80 years of age numbered about 60 300.1 This is projected to increase to about 123 900 by 2021,1 an increase of 106%. A 65% increase in the number of women over 80 years of age is expected in the same interval.

Our calculations show the limited preventive effect on increasing hip fracture incidence of an active interventional screening and therapy program for osteoporosis. Even with a relatively optimistic 60% screening and therapy compliance rate, hip fractures may still increase by about 55% compared with 1994-95. In view of the age of the target population (the average age of hip fracture patients in NSW is 82 years7), 40% capture and therapy compliance rates may be more realistic, suggesting that hip fractures may increase by 74% compared with 1994-95. It is also possible that capture and therapy compliance rates in the target population might not even achieve these levels. We also used the lowest of a number of population growth models.1 If faster population growth occurs, the increase in hip fractures will exceed our predictions, with correspondingly more serious implications for the healthcare system.

We assumed the screening technique would identify all patients at increased risk of hip fracture and all would be offered therapy. This optimistic assumption is almost certainly incorrect and thus our calculations overestimate the benefits of a screening program. On the other hand, compared with current drug regimens, advances in therapy may decrease fracture risk. Moreover, therapies with minimal toxicity and which have demonstrated benefit, such as vitamin D and calcium, could be applied widely to high risk patients in nursing homes and other institutions.2,13 However, the potential benefit of such an approach is limited, as, at present, only 29% of hip fracture patients are admitted from nursing homes and an additional 9% from hostels.7

Our analysis does not address the cost efficacy of a screening program for osteoporosis. Nor does it address the possible role of population education in preventing osteoporosis. Recent raised community awareness of osteoporosis may translate in the future into consumer-driven demand for preventive action from healthcare providers and more self- initiated prevention.

The recent increased demand for acute-care hospital beds in NSW has been partly met by reducing the average length of stay in hospital and increasing the number of day-only procedures. However, there is a limit to how much of the demand for hospital services can be met by these means. The average length of stay for hip fracture treatment in NSW has already been reduced from 31.5 days in 198018 to 11 days in 1995,7 and there is likely to be only limited additional gain from future efforts to reduce hospital stay for these patients.7

The increased number of hip fractures by 2021 will require considerable additional hospital resources, and, in view of the seasonal variation in hip fracture incidence,18 may impose an extreme burden on hospital services at certain times of the year. To cope with this, health service providers need to address the issue of future hospital bed availability for hip fractures. Failure to plan adequately may result in delay in treating other, less urgent, patients.

In conclusion, Australia, like other Western countries, must cope with the health problems of an ageing population in the early part of the next century, with osteoporotic hip fractures likely to be a major component of the expected increased demand for acute-care hospital services. A preventive program based on mass screening for osteoporosis and treatment of high risk individuals may have only a limited impact. While potentially of benefit, this approach would be insufficient by itself, and additional or alternative approaches to this problem, such as education of the community, need to be further explored.

References
  1. Australian Bureau of Statistics. Population projections for New South Wales 1997 to 2051. Canberra: ABS, 1998. (Catalogue No. 3222.0.)
  2. Wark JD. Osteoporosis: the emerging epidemic. Med J Aust 1996; 164: 327-328.
  3. Garton MJ, Cooper C, Reid D. Perimenopausal bone density screening -- will it help prevent osteoporosis? Maturitas 1997; 26: 35-43.
  4. Kanis JA. Assessment of fracture risk and its application to screening for postmenopausal osteoporosis: synopsis of a WHO report. Osteoporos Int 1994; 4: 368-381.
  5. Tosteson AN, Rosenthal DI, Melton LJ, Weinstein MC. Cost effectiveness of screening perimenopausal white women for osteoporosis: bone densitometry and hormone replacement therapy. Ann Intern Med 1990; 113: 594-603.
  6. Black DM. Why elderly women should be screened and treated to prevent osteoporosis [review]. Am J Med 1995; 98 Suppl 2A: 67S-75S.
  7. March L, Chamberlain A, Cameron I, et al. Prevention, treatment and rehabilitation of fractured neck of femur. Health Outcomes Project 1996. Sydney: Public Health Unit, Northern Sydney Area Health Service, 1996 (ISBN 07310 9633 9). Updated information provided by personal communication. Also on the internet <http://www.mja.com.au/public/issues/iprs2/march/fnof.pdf>
  8. Barratt AL, Cockburn J, Redman S, et al. Mammographic screening: results from the 1996 National Breast Health Survey. Med J Aust 1997; 167: 521-524.
  9. Salzman C. Medication compliance in the elderly. J Clin Psychol 1995; 56 Suppl 1: 18-22.
  10. McElnay JC, McCallion CR, al-Deagi F, Scott M. Self-reported medication non-compliance in the elderly. Eur J Clin Pharmacol 1997; 53: 171-178.
  11. Wren BG, Brown L. Compliance with hormonal replacement therapy. Maturitas 1991; 13: 17-21.
  12. Rozenberg S, Vandromme J, Kroll M, et al. Compliance to hormone replacement therapy [review]. Int J Fertil Menopausal Stud 1995; 40 Suppl 1: 23-32.
  13. Black DM, Cummings SR, Karpf DB, et al. Randomised trial of alendronate on risk of fracture in women with existing vertebral fractures. Lancet 1996; 348: 1535-1541.
  14. Seeman E. Osteoporosis: trials and tribulations [review]. Am J Med 1997; 103 Suppl 2A: 74S-87S.
  15. Randell A, Sambrook PN, Nguyen TV, et al. Direct clinical and welfare costs of osteoporotic fractures in elderly men and women. Osteoporos Int 1995; 5: 427-432.
  16. Lord SR. Femoral neck fractures: admissions, bed use, outcomes and projections. Med J Aust 1996; 145: 493-496.
  17. Lord SR. Hip fractures: changing patterns in hospital bed use in NSW between 1979 and 1990. Aust N Z J Surg 1993; 63: 352-355.
  18. Lau EM, Gillespie BG, Valenti L, O'Connell D. The seasonality of hip fracture and its relationship with weather conditions in New South Wales. Aust J Public Health 1995; 19: 76-80.

(Received 13 Nov 1998, accepted 13 Mar 1999)

Authors' details Department of Nuclear Medicine and Bone Densitometry, St Vincent's Hospital, Sydney, NSW.
Nicholas A Pocock, MD, FRACP, Senior Staff Specialist.
Nicole L Culton, BAppSc, Research Officer.
Neil D Harris, BA(Comm), RN, Research Officer.

Reprints will not be available from the authors.
Correspondence: Associate Professor N A Pocock, Department of Nuclear Medicine and Bone Densitometry,
St Vincent's Hospital, Sydney, NSW 2010.
Email: n.pocockATunsw.edu.au

©MJA 1999
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How many hip fractures can we prevent in New South Wales

Methods

To determine the predicted NSW population of those aged 65 years and over in 2021, we used the most recent Australian Bureau of Statistics population projections (low population growth model).1

To calculate the likely absolute numbers of hip fractures in 2021, we assumed similar age-adjusted hip fracture rates to those currently found in NSW.7 In women, the annual incidence of hip fractures in NSW (based on figures for 1995-96) ranges from 1.77/1000 in the 65 to 69 years age group, to 33.21/1000 in the over-85 group.7 In men, the respective rates are 1.01/1000 and 18.45/1000.7 These hip fracture incidences were applied to the NSW population predictions to derive the expected number of hip fractures in 2021 for the low population growth model.

It is difficult to estimate the likely capture rate of an osteoporosis screening program (ie, the proportion of the target population using the service), as the population at risk of osteoporotic fractures is generally older than those targeted by current screening programs (eg, mammographic screening for breast cancer). In addition, an osteoporosis screening program would need to include men, and no comparable screening programs for men currently exist in Australia. In the absence of a more suitable model, a recent study of the data from the 1996 National Breast Health Survey reported that about 50% of the target population have participated in the Program within the past two years.8 For our analysis we have made projections using 10%, 20%, 40%, 60% and 80% population capture rates.

There is no current consensus on the best osteoporosis screening program. For our study, however, we assumed a hypothetical best-case scenario in which the screening technique would identify all patients at increased risk of fracture, and therapy would be offered to all at-risk subjects.

Reported compliance rates for long term medical therapy vary widely.9 While figures of up to 80% have been reported,10 particularly with medications which have few side effects, lower compliance rates are more common for medications with adverse or unpleasant side effects (eg, hormone replacement therapy).11,12 There are few data available on long term compliance with therapy for osteoporosis, such as bisphosphonates, calcitriol or the latest generation of selective oestrogen receptor modulators.

The possible efficacy of a screening and treatment program was calculated separately for compliance rates of 20%, 40%, 60% and 80%. The efficacy of a treatment program targeted at high risk individuals depends not only on compliance with therapy, but also on drug efficacy. Available data suggest that current therapies for osteoporosis may have about 50% efficacy in reducing fractures.13,14 While it is possible that more effective therapeutic regimens will become available in the future, we used a value of 50% drug efficacy.

Results

In 2021, the projected age-specific NSW population for men and women over the age of 65 years (low population growth model) is shown in Table 1.1 Based on these population figures, and on recent data on age-specific admission rates for hip fractures,7 by 2021 we predict there will be about 9800 hip fracture admissions annually in NSW in subjects aged 65 years and older (Table 2). This is an increase of about 89% above current levels and compares with an expected 14% to 22% increase in the entire NSW population during the same period.1 In Table 3 the impact of an osteoporosis screening program and effective therapy in 2021 is shown for NSW men and women over 65 years at different capture rates and therapy compliance levels. The potential efficacy of a screening program would vary widely depending on population capture rates and therapy compliance. With an optimistic 60% population capture rate and 60% long term therapy compliance, with the low population growth model, a screening program might potentially prevent 1767 admissions for hip fractures. In this situation, hip fracture admissions in NSW in 2021 would still be 55% higher than in 1994-95.

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