Clinical characteristics of the reduced bone mineral density subgroup among adults with type 2 diabetes mellitus: a retrospective cross-sectional study

Abstract

Skeletal fragility in type 2 diabetes mellitus (T2DM) is incompletely represented by areal bone mineral density (BMD). We defined an operational reduced-BMD subgroup using routine hospital information-system data and examined whether routinely available clinical variables showed incremental associations and whether complex classifiers improved internal discrimination beyond age and sex. This single-center retrospective cross-sectional analysis included 329 de-identified analytical records from adults with T2DM who underwent routine dual-energy X-ray absorptiometry. The operational reduced-BMD subgroup was defined by the lowest T-score among the lumbar spine L1-L4, femoral neck, and total hip: records with at least one site-specific T-score ≤ − 1.0 were classified into the subgroup, and a stricter < -1.0 definition was examined as a boundary sensitivity analysis. Because menopausal status and Z-scores were unavailable, this rule was treated as an operational subgroup definition rather than a universal clinical diagnosis. Descriptive analyses, deliberately parsimonious Jeffreys-prior bias-reduced logistic models, fixed-unit age sensitivity analyses, and repeated nested internal classification were performed. Twenty-six records (7.9%) met the primary operational definition and 22 met the stricter definition; no record met a T-score ≤ − 2.5 threshold at the retained primary sites. Twenty-five of the 26 records in the reduced-BMD subgroup were from women. In the prespecified full-cohort model, age had an odds ratio (OR) of 5.39 per within-sample standard deviation (95% profile-likelihood confidence interval [CI], 2.71–12.15), and the female-sex estimate was large but imprecise (OR, 34.47; 95% CI, 8.29-321.11). On a common five-year scale, the age OR was 2.33 (95% CI, 1.65–3.50) in the full cohort and 2.29 (95% CI, 1.60–3.47) among records aged ≥ 50 years. The fixed age-sex classifier had a median internally validated ROC AUC of 0.921 (range, 0.915–0.923), decreasing to 0.901 (range, 0.897–0.904) in the age ≥ 50 subset. Among the tested algorithms and prespecified features, no complex classifier materially exceeded the fixed age-sex benchmark. In this selected single-center record-level dataset, the operational reduced-BMD subgroup was characterized principally by older age and marked female predominance. Restriction to age ≥ 50 years reduced apparent discrimination because of narrower case mix, while the age association remained similar on a fixed five-year scale. The additional tested variables did not provide precisely estimated incremental associations in the prespecified age-sex-plus-one-variable models, and the tested complex classifiers did not materially improve internal discrimination over the age-sex benchmark. All classification estimates were internally validated only, and the findings do not support causal, diagnostic, prognostic, deployment, or treatment claims. The operational reduced-BMD subgroup comprised 26 of 329 analytical records from adults with T2DM. Twenty-five of the 26 reduced-BMD records were from women, and all occurred at age ≥50 years. Jeffreys-prior bias-reduced logistic regression addressed sparse outcomes and near-separation. The age association was similar in the full cohort and the age ≥50 subset when expressed per five years. Within internal validation, the tested complex classifiers did not materially outperform the age-sex benchmark.