Empirical Project: Investigating the onset and trajectory of Alzheimer’s disease in Down syndrome

Abstract

Three decades of data, collected at a community learning disability service in a region of the UK, are reported on. Participants included 579 people with Down syndrome (DS), who were followed up from baseline to the point of a dementia diagnosis, and in some cases until death. Since most people with DS develop Alzheimer’s disease (AD), the aim was to see whether certain neuropsychological measures were changing in the prodromal stages of AD, above that of normal ageing, to support timely diagnoses. Variables associated with earlier age at dementia onset and subsequent survival times were also assessed. Generalised linear mixed models in R were used to compute prodromal changes for 204 of the sample, who had more than two complete assessments. Regression and hazard regression models in SPSS were used for onset (n= 279) and survival times (n= 185), respectively. Results suggest that difficulties with lexical-retrieval and visual memory may be early indicators of later AD. Awareness of the level of intellectual disability appears essential, since profound disability produced ‘floor’ effects, which impacted on the possibility for later declines. Earlier age at first assessment and living with family were predictive of an earlier age at diagnosis, which then led to longer duration of life, post-diagnosis. Both earlyand late-onset epilepsy, and living in a long-stay hospital were associated with earlier mortality. Implications for clinical practice and research are discussed.