Abstracts

Rationale: Many studies have identified an association between long-term AED use and bone disease. However, a cause and effect relationship for AEDs has not yet been established. We conducted a cross-sectional study to investigate the role of the duration of AED therapy and its impact on bone by assessing the difference in bone health parameters in two AED-treated populations, comparing newly-diagnosed epileptic patients taking an AED short-term (≤6 months), to those on longer-term AED monotherapy (>6 months). Methods: Dual energy Xray absorptiometry (DXA) (Hologic 4500A) was utilised to measure areal bone density (aBMD) at the lumbar spine (LS), total hip (TH), femoral neck (FN),and total body (TB).Total body bone mineral content (TBBMC) was also assessed. Peripheral quantitative computed tomography (pQCT) scans were performed at the 4% and 38% distal non-dominant radial and tibial sites to evaluate trabecular and cortical volumetric bone mineral density (TrD, CoD g/cm3) polar and axial stress strain indexes (SSI pol, SSIx, SSIy mm3) and cortical thickness (Cort Thk g/cm3).Parametric independent t-tests (two tailed) were employed to assess population mean differences. Results: The study sample consisted of 92 individuals taking a single AED for epilepsy: The two study populations comprised of 34 short-term (56% male, 44% female) and 58 longer-term (59% male, 41% female) AED-taking participants. From this study sample all DXA and 62 pQCT scans were available for analysis. Data were normally distributed and adjusted for age, height and weight. There was no significant difference between groups in age, height and weight.Short term AED-taking population, mean (±SD): 42.1 years ± 14.1; 170 cm ± 10.3; 79.7 kg ± 17.3. Longer-term AED-taking population: 44.3 years ± 17.3; 170 cm ± 9.3; 79.3 kg ± 15.8. THaBMD presented a highly-significant difference,with those on longer-term AEDs exhibiting lower values (0.97 ± 0.014 g/cm2, mean ± SEM) than short-term users (1.05 ± 0.018), p=0.002 (two tailed). TBaBMD was marginally different between short-term (1.14 ± 0.018 g/cm2) and long-term users (1.10 ± 0.013), p=0.051 (two tailed). The 4% tibial TrD was the only pQCT parameter to display a highly-significant difference between groups, with long-term users (244.36 ± 5.55 mg/cm3) exhibiting markedly lower values than their short-term counterparts (583.71 ± 11.53), p<0.01 (two tailed). Conclusions: Patients on longer-term AED therapy show significant differences in bone measures at several sites relevant to fracture risk in the longer-term users. Prospective monitoring of patients anticipated to require long-term AEDs may be of use in early detection of this clinically important condition.