Abstracts

Antiepileptic medication (AED) usage is well established to be associated with a change in total body weight. Valproate (VPA) users in particular are prone to weight gain. Other AEDs, such as topiramate, are associated with weight loss while lamotrigine is weight-neutral. The mechanisms for AED-associated weight changes are unknown. It is now recognized that changes in the distribution of body fat have important health implications independent of total body weight, specifically the association of increased relative abdominal fat as a risk factor for cardiovascular disease. Dual energy x-ray absorptiometry (DEXA) has proven a valuable tool in the assessment of body fat distribution, but has not been applied to the study of the effects of AED use on the distribution of body fat. The aim of this study was to utilize an AED usage-discordant twin and matched sister approach to examine this issue. 16 twin (9 monozygous,7 dizygous) and 3 sister pairs discordant for [gt]12 months of any AED use with a mean(SD) age of 37.8(16.0) were included. Body composition including fat distribution was acquired using DEXA scanning (Hologic 4500A/1000W). The abdominal region was defined as the area extending from the superior surface of the 2nd lumbar vertebra to the inferior surface of the 4th lumbar vertebra and laterally to the inner aspect of the ribcage. Conventional whole body analysis was used to determine total body and trunk fat. Abdominal fat was expressed as a percentage: of the abdominal region (Afat%); of total trunk fat (AfatTT%); of total body fat (AfatTB%). Height and weight were measured. Paired t-tests (two-tailed) were used to test for within-pair differences. There was no significant within-pair difference in height, weight, total body fat and lean mass. There was a within-pair difference (AED user vs. non-user) in AfatTB% (6.6% vs. 5.6%, p=0.038) and in Afat% (25.1% vs. 20.0%, p= 0.079). Pairs discordant for [gt]2 years of AED use (n=16) had a within-pair difference in AfatTT% (18.5% vs. 16.3%, p=0.038), AfatTB% (6.7% vs. 5.5%, p=0.030) and within-pair difference in Afat% (23.8% vs. 18.3%, p=0.057). The within-pair difference in current valproate users (n=7) was similar to that of non-valproate AED users (n=12) for weight, height and the fat distribution. AED users have altered body fat distribution compared to non-users, with an increase in the relative proportion of abdominal fat, independent of differences in body weight. There was no relationship to the type of AED used, with valproate users showing similar changes to non-valproate AED users. This novel finding demands further investigation and may have important health implications particularly for risk of cardiovascular disease in this population.