Abdominal Aortic Calcification May Further Raise Known Fracture Risk

Steve Cimino

March 23, 2021

A new study has found that older men with high levels of abdominal aortic calcification (AAC) and a prevalent vertebral fracture — both of which can be assessed via lateral spine radiographs — are at increased risk of hip, clinical vertebral, and major osteoporotic fractures.

"The results of this study and others suggest that it may be appropriate to expand lateral spine imaging to include those with a significant pre-test probability of higher AAC being present," wrote John T. Schousboe, MD, of the Park Nicollet Clinic and HealthPartners Institute in Bloomington, Minn. The study was published in the Journal of Bone and Mineral Research.

To determine the impact of prevalent vertebral fractures and AAC on fracture risk, the researchers assessed the lateral spine radiographs of 5,365 men who were enrolled in the Osteoporotic Fractures in Men (MrOS) study. All participants were 65 years or older, community dwelling, able to walk without assistance, and without bilateral hip arthroplasties. They split patients' 24-point AAC (ACC-24) scores at the baseline visit into four levels: 0-1, 2-4, 5-8, and greater than 9. Self-reports of fractures were solicited from the cohort every 4 months.

Of all participants, 7.6% (n = 407) had a prevalent vertebral fracture at baseline. They were, on average, 1.5 years older than participants without a fracture; they were also more likely to be white and to have a prior nonspine fracture, along with having a lower femoral neck BMD (0.718 g/cm2, compared with 0.787 g/cm2P < .001). In addition, significantly more men with a prevalent vertebral fracture had an AAC score greater than 9 (27% vs. 21.2%).

After an average follow-up period of 12.4 years (standard deviation, 5.2), 634 men had a major osteoporotic fracture, 283 had a hip fracture, 206 had a clinical vertebral fracture, and 2,626 died without having any of the three. After adjustment for risk factors such as age, prior nonspine fracture, and prevalent vertebral fracture, men with higher AAC-24 scores had a higher risk of major osteoporotic fracture, compared with men who had scores of 0-1: a hazard ratio of 1.38 (95% confidence interval, 1.10-1.73; P < .001) for scores 2-4, a HR of 1.45 (95% CI, 1.14-1.84; P < .001) for scores 5-8, and a HR of 1.65 (95% CI, 1.29-2.10; P < .001) for scores greater than 9.

Similar findings were reported regarding risk of hip fractures: a HR of 1.54 (95% CI, 1.07-2.20; P < .001) for men with AAC-24 scores 2-4, a HR of 1.40 (95% CI, 0.96-2.06; P < .001) for scores 5-8, and a HR of 2.17 (95% CI, 1.50-3.13; P < .001) for scores greater than 9. AAC-24 score severity was not associated with a higher risk of clinical vertebral fractures.

After adjustment for risk factors and AAC-24 score, men with prevalent vertebral fractures had an increased risk of all three fracture outcomes, compared with men without any fractures at baseline: a HR of 1.56 (95% CI, 1.12-2.16; P < .001) for hip fracture, a HR of 1.85 (95% CI, 1.48-2.31; P < .001) for major osteoporotic fracture, and a HR of 2.76 (95% CI, 1.94-3.91; P < .001) for clinical vertebral fracture.

Adjusting for competing mortality produced similar results: men with higher levels of AAC had increased risk of major osteoporotic fracture and hip fracture, although AAC-24 score was not associated with higher risk of clinical vertebral fractures. Prevalent vertebral fractures were also still associated with higher risk of hip (subdistribution HR, 1.42; 95% CI, 1.01-2.00; P = .004), major osteoporotic fracture (SHR, 1.71; 95% CI, 1.36-2.14; P < .001), and clinical vertebral fracture (SHR, 2.46; 95% CI, 1.72-3.52; P < .001).

Fracture Risk Assessment Proves to Be "A Nice Proof of Concept"

Dr Thomas Link

"It's well known that prevalent fractures predict future fractures," said Thomas M. Link, MD, PhD, chief of the musculoskeletal imaging section in the department of radiology and biomedical imaging at the University of California, San Francisco, in an interview. "The new finding is that aortic calcifications combined with prevalent fractures perform better in predicting major osteoporotic fractures. Traditionally on radiographs, we note that patients who have more calcifications in vessels have less density or calcium in the bone, so this is a nice proof of concept."

"While the study shows excellent reproducibility, it is not clear how the AAC-24 score was validated," he added. "Theoretically, abdominal CT could be used for this."

Along with validation of the AAC-24 score on lateral spine radiographs, he expressed a desire that future research would be "clearer regarding how this would potentially impact patient management. Prevalent fractures already are an indication to treat patients with osteoporosis-specific drugs. How would the results of this study impact management beyond that?"

The authors acknowledged their study's other potential limitations, including limits in their ability to estimate absolute and relative hip fracture risk in men with low AAC scores but a prevalent vertebral fracture. In addition, they noted that their cohort was "mostly white, healthy, community-dwelling older men" and therefore may not be generalizable to other populations.

The study was supported by the National Institutes of Health, including grants from the National Institute on Aging, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, the National Center for Advancing Translational Sciences, and the NIH Roadmap for Medical Research. One author reported being supported by a National Heart Foundation of Australia Future Leader Fellowship. The others disclosed no potential conflicts of interest.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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