Longitudinal trajectories of dietary quality and cognitive performance in older adults: Results from a 6-year cohort study

Abstract

Diet affects cognitive performance, but most previous studies only assessed diet once. Trajectory analysis of diet measured at multiple timepoints can identify subpopulations requiring more interventional efforts. We thus assessed associations between dietary trajectories and cognitive performance in older adults. This was a 6-year prospective cohort study involving 356 ethnically Chinese, non-demented, community-dwelling older adults recruited between 2011 and 2013. At baseline and at 4th- and 6th-year follow-ups, dietary intakes of the participants were assessed using food frequency questionnaires. Dietary quality was graded using the modified Alternative Healthy Eating Index (mAHEI) with seven components; longitudinal trajectories of dietary quality were derived using latent growth mixture modelling. Outcomes were global- and domain-specific cognitive performance (attention, memory, executive functions, and verbal fluency). Multivariable regressions adjusting for important covariates (sex, age, energy intake, APOE risk alleles, depressive symptoms, and body mass index (BMI)) assessed associations between the dietary trajectories and cognitive outcomes. Included participants had a mean age of 71.6 years and a mean BMI of 23.8kg/m2. Three mutually exclusive dietary quality trajectories, namely "deteriorating", "improving", and "stable-high", were derived. Compared with the stable-high trajectory, the improving trajectory was associated with a lower z-score for the memory domain (β:-0.403; 95% CI:-0.656,-0.151; P=0.002), which was consistently observed for the four individual tests of the domain (β range:-0.324 to-0.448; all P<0.05). In unadjusted analysis, the deteriorating trajectory was associated with a 0.369 lower z-score for the verbal fluency domain (95% CI:-0.700,-0.039 P=0.028), though attenuated to borderline significance with adjustment for covariates. Sex and BMI modified some of these associations. No other associations were observed for global cognition or other cognitive domains. In Taiwanese older adults, consistently high dietary quality is associated with better cognitive performance. Interventions to promote and sustain better dietary quality over time can have substantial impacts on cognitive function.