Early-onset versus late-onset Alzheimer’s disease in tunisia

Abstract

Previous reports stated globally that approximately 10% of Alzheimer's disease cases present before 65 years old. Whether early and late onset Alzheimer's were “one entity or two” still questionable. Our aim was to determine prevalence of Early Onset Alzheimer's Disease (EOAD) and to compare its demographic and genetic characteristics to Late-Onset Alzheimer's Disease (LOAD) in Tunisia. In an observational study, we retrospectively reviewed the database of 1065 AD patients followed at the memory clinic of Razi Hospital-Tunisia between July 2002 and August 2014 (12 years). Two groups (EOAD and LOAD) were defined upon patients symptoms arousal before or after the age of 65. Demographic, clinical and pedigree data of patients were compared. 209 EOAD (19.6%) and 775 LOAD (72.7%) were identified. Mean age at onset was 57.3 years for group 1 and 75.1 years in group 2. Sex ratio was respectively 0.97 and 0.7. Mean MMSE at diagnosis was higher in EOAD group (14/30 Vs 12/30 for LOAD) but also was the mean time for diagnosis (4.1 year Vs 3.4 year for LOAD). A positive familial history of dementia was found in 41.3% of EOAD versus 44.7% for LOAD. Familial AD was found in 36.8% of EOAD Vs in 40.3% LOAD with a majority of non mendelian heredity for both groups (72.8% Vs 73.4%). However AD inheritence was higher in group1 (=21.4% Vs 13.7%) while AR one in group 2 (5.6% Vs 12.7%). Prevalence of EOAD in Tunisia seems to be higher than expected. We did not found significant differences between the two groups despite in the sex-ratio. Further investigations should focus on symptomatic and gentic differences.