Association of coexisting type 2 diabetes and DXA-defined low muscle mass with prevalent radiographic vertebral fracture in community-dwelling older adults: a cross-sectional study.

Background: Prevalent radiographic vertebral fracture is frequently clinically unrecognized in older adults, and areal bone mineral density does not fully characterize its distribution. Whether coexisting type 2 diabetes mellitus (T2DM) and objectively measured low muscle mass identify a subgroup in which this burden is concentrated remains unclear. Methods: This community-based cross-sectional analysis included 1,642 adults aged 65 years or older recruited through 16 community health service centers covering 36 administrative communities in Changchun, China, between July 2021 and March 2023. Participants were classified into four mutually exclusive groups: neither condition, T2DM alone, dual-energy X-ray absorptiometry (DXA)-defined low muscle mass alone, or both conditions. The primary outcome was prevalent radiographic vertebral fracture (Genant grade ≥ 1), with Genant grade ≥ 2 fracture as the key secondary outcome. Modified Poisson models estimated prevalence ratios (PRs). The primary model included age and body mass index as restricted cubic splines, sex, and current smoking, with covariance estimation accounting for 36 community clusters. Missing covariates were handled using 50 datasets generated by multiple imputation by chained equations, and marginal standardization was used to estimate prevalence differences. Results: The analytic cohort included 343 participants (20.9%) with prevalent radiographic vertebral fracture. The coexisting phenotype comprised 14.1% of the cohort but accounted for 31.5% of all Genant grade ≥ 1 events and 35.2% of all Genant grade ≥ 2 events. Observed prevalence was 11.5, 20.7, 24.2, and 46.6% in the neither-condition, T2DM-alone, low-muscle-mass-alone, and coexisting groups, respectively. Primary-model PRs versus neither condition were 1.66 (95% CI, 1.30-2.12), 1.92 (95% CI, 1.42-2.59), and 3.63 (95% CI, 2.81-4.68), respectively. The coexisting phenotype had a standardized prevalence of 44.1% (95% CI, 38.3-49.9%) and a prevalence difference of 31.9 percentage points (95% CI, 25.3-38.5) versus neither condition. Results were similar in the femoral-neck-BMD-context, complete-case, Genant grade ≥ 2, and no-prior-fracture analyses. Conclusion: In this analytic sample, coexisting T2DM and DXA-defined low muscle mass defined a relatively small subgroup with a disproportionate share of prevalent radiographic vertebral fracture events and the highest fracture prevalence. These cross-sectional findings do not establish causality, future fracture prediction, screening performance, or an indication for vertebral imaging.