5120 Contribution Of Proximal Femur Geometry And Bone Density Distribution To Hip Fragility In Adults ≥ 50yrs With Longstanding Type 1 Diabetes
Authors: Johannesdottir F , D’Mello C , Murthy A B , Zahedi B , Engelke K , Bouxsein M L , Yu E W 
Published: October 2024

Disclosure: F. Johannesdottir: None. C. D’Mello: None. A.B. Murthy: None. B. Zahedi: None. K. Engelke: None. M.L. Bouxsein: None. E.W. Yu: Grant Recipient; Self; Amgen Inc.

Introduction: Adults with type 1 diabetes (T1D) have a 6-fold increased risk of hip fracture, which is explained only in part by lower areal bone mineral density (aBMD) by DXA. We hypothesize that femoral geometry and regional bone deficits at the proximal femur contribute to higher hip fracture risk in older adults with T1D. Further, we determine the influence of age at T1D diagnosis on femoral bone density and structure. Methods: We enrolled 97 individuals with T1D and 53 non-diabetic controls (CON) as part of the T1D Bone Health Connection (BEACON) Study, an ongoing prospective study of adults aged ≥50 years. We obtained computed tomography (CT) scans of the proximal femur (in-plane pixel size 0.98x0.98 mm, 1.25 mm slice thickness) to measure total (Tt), trabecular (Tb) and cortical (Ct) volumetric BMD (vBMD); and volume (Vol) and Ct thickness (Th) in several regions, including total hip, femoral neck (FN), trochanter (TR) and intertrochanter (IT) (Medical Image Analysis Framework, University of Erlangen, Germany). We also assessed total hip and FN aBMD by DXA. We employed ANCOVA models to compare bone outcomes between T1D and controls with adjustment for age, height, and weight, stratified by sex. When comparing bone outcomes within T1D, we adjusted for age, height, weight, and sex. Differences are reported as % difference between the least-square means for the groups. Results: The average age of participants was 64±7 yrs, and similar between T1D and CON (p=0.21). Male T1D were shorter than male CON (173 cm vs 176 cm, p=0.05), but with similar weight (p=0.73). Female T1D were heavier than female CON (71 kg vs 64 kg, p=0.03). The T1D cohort included 50 men and 47 women with mean diabetes duration of 46±10 yrs, mean A1c 7.1±1.0%, and median age at onset 17 yrs (IQR:10-25). Among T1D, 31 (52% female) were diagnosed ≤ age 12. Among men, total hip and FN aBMD did not differ by group, but T1D had smaller FN Tt.Vol (9%) and FN width (8%) (p&lt;0.05 for all). In contrast, there were no differences between T1D and CON in the female cohort, neither by DXA nor CT (p≥0.13). Of note, T1D men appeared to have more poorly controlled diabetes than women (29% of men vs 11% women had A1c ≥8%, p=0.03). Within T1D, those who were diagnosed ≤ age 12 had lower Tb.vBMD (16-18%) at the total hip, TR and IT regions (p&lt;0.05) and tended to have lower Tb.vBMD (16%, p=0.06) at the neck compared to those diagnosed at a later age, but no differences in DXA aBMD (p&gt;0.31). Conclusion: In sum, older men, but not women, with T1D showed some deficits in bone structure at the proximal femur. Adults with T1D who were diagnosed ≤ age 12 had trabecular bone deficits within the proximal femur. Additional studies are needed to identify mechanisms underlying the high hip fracture risk in T1D.

Presentation: 6/1/2024