Correlations among cognitive and behavioural assessments in patients with dementia due to Alzheimer's disease

• Schooling impacted cognitive test scores, but not functionality or behaviour.
• Lower education and early life smoking and alcohol use led to higher rates of late life smoking and alcohol use.
• Apathy was higher for heavy alcohol users, while hallucinations increased with dementia severity.
• The Clock Drawing Test is more useful in early dementia stages, while the SMMSE is more useful in severe dementia.
• Cognition, functionality and behaviour, but not caregiver burden, are usually interrelated in all dementia stages.

AimsPrimarily, we sought to verify correlations among assessments for cognition, behaviour and functional independence in a sample of patients with dementia due to Alzheimer's disease (AD). Secondarily, impacts of education, APOE haplotypes, length of dementia, age and alcohol use over the neuropsychiatric assessment were estimated.MethodsPatients with AD were assessed for demographic features, neuropsychiatric symptoms, cognitive test scores, functional impairment, caregiver burden and APOE haplotypes. Statistical comparisons were undertaken by way of Kruskal–Wallis test, linear regressions and Spearman correlations, significance at ρ < 0.05.ResultsA total of 217 patients were included. Mean schooling was 4.21 ± 3.7 years, with significant impacts over cognitive tests. Mean age at examination was 78 ± 6.19 years-old, significantly influencing instrumental functionality. The mean length of the dementia syndrome was 5.4 ± 2.9 years, significantly impacting cognitive decline and functionality. Apathy was the most common behavioural symptom, negatively correlated with anxiety and delusions, and positively correlated with lifetime alcohol load. Patients with previous smoking or drinking habits were more likely to continue smoking or drinking later in life. APOE4+ haplotypes led to earlier dementia onset and significantly lower caregiver burden in mild dementia stages.ConclusionsMost correlations among test results were highly significant, confirming that cognition, behaviour and functionality are usually interrelated in all stages of AD. Caregiver burden was correlated with behaviour, but not with cognition, and was lower for patients with APOE4+ haplotypes in mild dementia stages. Education is a major impact factor for cognitive performance.