Differences between early and late onset Alzheimer's disease

Abstract

Previous studies comparing early-onset Alzheimer's disease (EOAD) and late-onset AD (LOAD) have been limited by cross-sectional design and a focus on isolated clinical variables. This study aims to explore differentials in clinical features between EOAD and LOAD and to examine longitudinally trends in cognitive function. Data from 3,747 subjects with AD from C-Path Online Data Repository was used to compare demographics, body mass index (BMI), mean arterial pressure (MAP), biochemistry and cognitive assessments, including mini-mental state examination (MMSE) and Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-Cog), between EOAD and LOAD. The baseline differences were examined by binominal proportion test and t-test. The trends of cognitive functions, evaluating by MMSE and ADAS-Cog, were examined by the mixed model, controlling for the effect of repeated measures of the same person. No significant difference was found in BMI and MAP. C-reactive protein, creatinine and blood urea nitrogen (BUN) (p<0.05) were significantly higher in LOAD. The APOE ε4 alleles was more likely to be found among LOAD compared to APOE ε2 or APOE ε3. EOAD had significantly lower MMSE at baseline and this difference significantly increased over time. Despite an insignificant differential in ADAS-Cog between EOAD and LOAD at baseline, the differential was enlarged gradually and became more significant with time. Our findings suggest that elevated inflammatory markers, impaired renal function and APOE ε4 alleles are overrepresented in LOAD, possibly indicating that different factors determine the development of EOAD and its more rapid cognitive deterioration.

Keywords: Alzheimer’s disease; EOAD prognosis; Early-onset dementia; cognitive assessments; late-onset dementia.

Figure 1

The trend of MMSE and ADAS-Cog over time by LOAD versus EOAD.