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High BMD independently associated with knee, hip OA
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CHICAGO — High estimated bone mineral density of the heel and femoral bone density were associated with an increased risk for osteoarthritis of the knee and hip, according to research presented at the ACR/ARHP 2018 Annual Meeting.
Thomas Funck-Brentano, MD, PhD, of the Centre for Bone and Arthritis Research at the University of Gothenburg, Sweden, said the trial is the first to provide evidence of a causal effect between femoral bone mineral density (BMD) and OA.
“The involvement of bone in the early stage of OA or its progression has been a matter of debate during the past decade,” he said. “Results from cross-sectional studies are consistent, showing a positive association between BMD and OA prevalence. However, the direction of this association is unknown and may be affected by some confounders.”
According to Funck-Brentano, patients with high bone mass are more likely to undergo joint replacement therapy and have radiographic OA at the knee and hip.
“But when you look into more detail, the association is not necessarily between the presence of joint space narrowing,” he said. “The results are less clear with prospective studies, with BMD being inconsistently associated with increased incident OA. With regard to radiographic knee OA progression, BMD seems to be protective.”
To help clarify these inconsistent results, Funck-Brentano and colleagues used data from the UK Biobank to compare observational and causal links between BMD and OA at different sites. Their analysis included 384,838 participants of white European descent.
The researchers used an ultrasound to estimate BMD at the heel. This technique involved speed of sound and broadband ultrasound attenuation. They also performed mendelian randomization analyses to assess for causality, using genetic instruments as proxies for femoral neck BMD and lumbar spine BMD.
Overall, 12.6% (n = 48,431) of participants had OA. Among them, 5.1% (n = 19,727) had knee OA, 3.1% (n = 11,875) had hip OA, and 0.6% (n = 2,330) had hand OA. The data revealed a greater risk for hand OA (OR = 2.83; 95% CI, 2.43-3.29), hip OA (OR = 1.38; 95% CI, 1.31-1.46) and knee OA (OR = 1.08; 95% CI, 1.03-1.13) among women vs. men.
Observational associations
An analysis adjusted for age, gender and BMI revealed an observational association between estimated BMD and OA. Specifically, an increase in estimated BMD by 1 standard deviation (SD) significantly increased the risk for all OA (OR = 1.03; 95% CI, 1.02-1.04), knee OA (OR = 1.07; 95% CI, 1.05-1.09) and hip OA (OR = 1.09; 95% CI, 1.07-1.11), but not for hand OA. The results were similar for incident OA and severe OA cases.
There was also an observational association between BMI and knee OA (OR = 1.69; 95% CI, 1.67-1.72), as well as hip OA (OR = 1.32; 95% CI, 1.30-1.34).
Causal associations
The researchers observed a causal effect of genetically-determined femoral neck BMD. There was an increased risk for all OA (OR = 1.14; 95% CI, 1.05-1.23), knee OA (OR = 1.18; 95% CI, 1.04-1.35) and hip OA (OR = 1.22; 95% CI, 1.09-1.37) for every 1 SD increase in femoral neck BMD. There was also a causal association between lumbar spine BMD and knee OA (OR = 1.18; 95% CI, 1.08-1.29), and a casual association between BMI and knee OA (OR = 1.76; 95% CI, 1.56-1.99), as well as hip OA (OR = 1.52; 95% CI, 1.31-1.78).
More research needed
In all analyses, there was no correlation between BMD or BMI and hand OA. However, Funck-Bretano indicated that more research is needed to confirm the relationships.
“I think the negative findings for OA of the hand must be taken with a lot of care because we were clearly underpowered,” he said. “The fact is that 2,000 cases is rather low, so we cannot really conclude the absence of a causal association.”
There were other limitations to the study, including the lack of data on physical activity and MRIs. In addition, the findings can only be applied to white European patients. Still, Funck-Bretano concluded that “estimated BMD at the heel is an independent risk marker for knee and hip OA, and femoral neck BMD is causally associated with knee and hip OA.
“In light of these results, strategies that intend increase BMD may not be beneficial for the prevention or treatment of OA in the general population,” he said. – by Stephanie Viguers
References:
Funck-Brentano T, et al. Abstract 956. Presented at: ACR/ARHP Annual Meeting, Oct. 20-24, 2018; Chicago.
Disclosure: Funck-Brentano reports no relevant financial disclosures.