Getting Hip to Screening
Abstract & Commentary
With Comment by Allan J. Wilke, MD, Associate Professor of Family Medicine, Medical College of Ohio, Toledo, OH, and Associate Editor, Internal Medicine Alert.
Synopsis: Screening for osteoporosis may result in fewer hip fractures.
Source: Kern LM, et al. Ann Intern Med. 2005;142:173-181.
The US Preventive Services Task Force’s most current recommendation regarding osteoporosis (2002) supports screening all women aged 65 years and older, despite concluding that treatment "would prevent a small number of fractures."1 This study adds evidence (albeit, inconclusive) to shore up that position. Kern and associates went back to the Cardiovascular Health Study (CHS), a longitudinal study that looked for heart disease risk factors in adults 65 years and older. It was conducted in 4 US locales: Sacramento, CA, Washington County, MD, Forsyth County, NC, and Allegheny County, PA. Subjects in Sacramento and Allegheny County were offered DEXA scans during 1994-1995. The subjects were followed for an average of 4.9 years with hip fracture as the outcome of interest. Exclusion criteria included institutionalization, homebound status, receiving cancer therapy, plans to relocate within 3 years, history of osteoporosis, history of hip fracture, and bisphosphonate use.
In 1994-1995, 4842 CHS participants were still alive, enrolled in the study, and showed up for their annual examination. After applying the exclusion criteria, 1422 participants from Sacramento and Allegheny were offered DEXA scans and 1378 accepted. The usual care group in Washington and Forsyth numbered 1685. Average age was 76 years, the participants were mostly women, and for most illnesses they were equally afflicted. However, the 2 groups were dissimilar. The screened group was less white, had better self-reported health, was more active, had higher scores on activities of daily living, used more calcium, multivitamins, and estrogen, used less benzodiazepines, and had higher cognitive scores. It also used more alcohol, less thiazide diuretics, and more thyroid hormone than the usual care group. The first set of circumstances would favor fewer hip fractures in the screened group, but the latter would favor the usual care group. Kern and colleagues tried to compensate for these differences by developing "propensity scores."
There were 33 hip fractures (incidence, 4.8 per 1000 person-years) in the screened group, and 69 fractures in the usual care group (8.2 per 1000 person-years). The adjusted hazard ratio was 0.64 (95% confidence interval [CI], 0.41-0.99) when men and women were considered together. There was a trend for decreased adjusted hazard ratios in both men (0.68; CI, 0.32-1.42) and women (0.61; CI, 0.35-1.06) that did not reach statistical significance. Risk stratification by sex, age, or race identified 2 subgroups where screening would be favored: white people (0.62; CI, 0.39-0.97) and people 85 years and older (0.22; CI, 0.06-0.79). However, their sensitivity analysis concluded that a "small unmeasured confounder" could weaken the association between screening and hip fracture.
In the year following their DEXA scan, screened participants whose DEXA scan revealed below average bone mineralization were more likely to start calcium supplementation or bisphosphonate therapy than participants whose bone mineralization was normal. Initiation of multivitamin use among the screened group was greater than the usual care group in that same year (11% vs 7%), and falls were fewer (16% vs 20%).
Comment
We’ve been hoping for the study that links screening for osteoporosis with decreased incidence of hip fracture—this isn’t it. In fact, an editorialist2 asserts that the "small unmeasured confounder" is real and identifies it as the "as-yet-unexplained geographic variation in hip fractures in the United States." The problem is that the CHS was not designed to answer the question of whether screening for osteoporosis reduces hip fractures. What we need is a randomized, controlled trial that directly addresses the question.
What we can deduce from this study, though, is that screening is associated with changes in health behaviors, including use of medications to increase bone mineralization and, perhaps, interventions to prevent falls. It is possible that the lower rate of falls was responsible for the decreased incidence of fracture. The fact that individuals 85 years and older benefited the most from screening should encourage us not to ignore this ever-growing segment of the population. Complicating the good news is that treatment of women 80 years and older with risedronate reduces the incidence of vertebral fractures, but not non-vertebral fractures.3,4
Will this study change your practice? As it currently stands, we don’t do a very good job screening at-risk women,5-7 let alone all women 65 years and older.
References
1. www.ahrq.gov/clinic/uspstf/uspsoste.htm. Accessed 03/20/2005.
2. Cummings SR. Ann Intern Med. 2005;142:217-219.
3. Boonen S, et al. J Am Geriatr Soc. 2004;52:1832-1839.
4. Wilke AJ. Internal Medicine Alert. 2005;27:1-2.
5. Andrade SE, et al. Arch Intern Med. 2003;163: 2052-2057.
6. Wilke AJ. Internal Medicine Alert. 2003;25:163-164.
7. www.surgeongeneral.gov/library/bonehealth/factsheet4.htm. Accessed 03/27/2005.
Screening for osteoporosis may result in fewer hip fractures.
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