Abstract
Background
The AIBL study is following 1112 individuals (768 healthy controls (HC), 133 with MCI and 211 with AD) prospectively, with cognitive testing, imaging, health and lifestyle dataand biomarker assays every 18 months. We report transition rates to MCI and AD and the emergence of other cognitive syndromes at 36 and 54 months of follow-up.
Methods
Every 18 months participants undertook detailed cognitive assessment, completed health and lifestyle questionnaires and gave 80 ml of blood. Initially one quarter underwent amyloid and MRI brain imaging at baseline and every follow-up.
Results
At 36 months 74.1 % (824) returned for assessment. Since baseline 73 had died and 215 did not return. At 36 months 610 were classified as HC, 56 as MCI and 154 as AD. There were 3 cases of vascular dementia and one of dementia due to Parkinson's disease. At 54 months 718 (64.6%) could have their diagnostic status determined, with 294 having withdrawn and 100 having died. There were 560 HCs, 51 MCIs, 102 ADs and 5 non-AD dementia cases at 54 months. HCs transitioned to MCI or AD at a rate of 4.6% by 36 and 6.6 by 54 months. At 36 months 35.3% of MCIs had developed AD.
Conclusions
Perhaps because the baseline HCs were well educated, healthy and with an average age of 70 at baseline, transition to MCI or AD from this group has been slow to date, but the development of AD in our MCI cohort has been within expected paramaters. Having AD or MCI was associated with an increased risk of death or drop out. We are currently collecting 72 month data and have expanded the cohort to compensate for thos who dropped out.