Abstract
Background
There has been increased interest in the role of dietary patterns and future risk of Alzheimer's disease (AD). However, the specific relationship between protein and fibre intake on cognitive function in older adults at higher risk of AD remains to be determined. This study investigated the association of protein and fibre intake, with cognition using data from the Australian Imaging, Biomarkers and Lifestyle study of ageing (AIBL) cohort.
Methods
Neuropsychological data derived from AIBL (734) were grouped into two cognitive domains (PACC and the Boston non-memory score). Composite scores, calculated by averaging the normalised individual cognitive measure Z scores, were assessed between levels of fibre and protein intake (binary, below/above the recommended daily intake (RDI) age, gender, APOE e4 allele status, total energy intake, education and BMI.
Results
Average values for the AIBL Study Preclinical Alzheimer cognitive (AIBL PACC) score (but not the non-memory) were significantly higher in participants with high protein intake (PACC:0.11 vs PACC:0.68, p=0.046) but not for those with high fibre intake (PACC:0.51 vs PACC:0.53, p>0.05). Adjusted for all confounding variables, this difference was abrogated (p>0.05). Given the level of education as a covariate was strongly related to the PACC score (p<0.0001), we further tested the interaction between education level (<12/12+ years) with low/high protein and fibre intakes. We saw a significant interaction for both protein and fibre groups with education level for the PACC score (education*protein: p=0.014, education*fibre: p=0.051), with those participants with high protein/fibre intakes and 12+ years of education having higher PACC scores as compared to those with <12 years of education and low protein/fibre intakes. Combining both fibre and protein in one three level variable (0=low fibre/low protein, 1=at least 1 fibre/protein high, and 2=both high fibre and protein) identified a significant association with the PACC score (p=0.007), with those participants in the low group and with <12 years of education performing worse for the PACC score as compared with those in the high group with 12+years of education.
Conclusions
This study highlights the importance of adequate protein and fibre intake on cognitive performance in an elderly cognitively normal population.