Impaired Bone Density and Quality in Type 1 Diabetes Mellitus: Prevalence and Key Clinical Correlations

<b>Background:</b> Type 1 diabetes mellitus (T1DM) is associated with an increased risk of fragility fractures that cannot be fully explained by reduced bone mineral density (BMD), highlighting a potential role for bone quality impairment. The purpose of this study was to evaluate the prevalence of altered bone density and microarchitecture and to identify their main clinical correlates in adults with T1DM and seemingly adequate glycemic control at the time of assessment. <b>Methods:</b> Sixty-eight adults aged 18-69 years with T1DM attending a diabetes technology outpatient clinic were enrolled in this single-center, cross-sectional study. BMD at the lumbar spine, femoral neck, and total hip was assessed by dual-energy X-ray absorptiometry (DXA) and classified as reduced based on age and sex: Z-score < -2.0 SD for premenopausal women and men < 50 years, and T-score ≤ -2.5 SD for postmenopausal women and men ≥ 50 years. Bone microarchitecture was evaluated using trabecular bone score (TBS). Clinical, metabolic, and lifestyle variables were collected, including glycated hemoglobin (HbA1c; good control ≈ 7.0%/53 mmol/mol), diabetes duration, microvascular complications, and physical activity (PA) assessed by the International PA Questionnaire (IPAQ; moderate-high PA defined according to combined high and moderate IPAQ categories). <b>Results:</b> Reduced BMD was observed in 35.3% of patients and was associated with older age (<i>p</i> < 0.001), longer disease duration (<i>p</i> = 0.044), lower body mass index (<i>p</i> = 0.031), poorer glycemic control (<i>p</i> = 0.03), microvascular complications such as diabetic peripheral neuropathy (<i>p</i> = 0.028) and retinopathy (<i>p</i> = 0.045), and low PA (<i>p</i> = 0.012). Altered TBS was present in 45.6% of patients and was associated with older age (<i>p</i> < 0.001), longer diabetes duration (<i>p</i> = 0.011), higher HbA1c levels (<i>p</i> < 0.001), diabetic peripheral neuropathy (<i>p</i> = 0.002), retinopathy (<i>p</i> = 0.007), cardiovascular risk factors (dyslipidemia <i>p</i> = 0.002, hypertension <i>p</i> = 0.002), and low PA (<i>p</i> < 0.001). In multivariable analyses, older age and higher HbA1c were independently associated with reduced TBS, whereas moderate-high PA was associated with a lower likelihood of impaired bone microarchitecture. <b>Conclusions:</b> Impaired bone density and bone quality are highly prevalent in adults with T1DM and are frequently associated with longer disease duration, poorer metabolic control, and chronic complications. Our findings support the potential value of a combined assessment of BMD and TBS in fracture risk evaluation, together with strategies aimed at preventing diabetes-related complications and promoting healthy lifestyle behaviors.