Undernutrition impacts on cognitive performance trajectories in older adults: the Collaborative PROMED-COG Pooled Cohorts Study

This study aimed to investigate the association between undernutrition and the trajectories of neurocognitive aging. This retrospective study uses harmonized data from two population-based longitudinal studies, the Progetto Veneto Anziani and the Italian Longitudinal Study of Aging. Both studies included a baseline and two follow-up evaluations over 9 years. Undernutrition was defined according to the Global Leadership Initiative on Malnutrition (GLIM) criteria, and cognitive function was assessed using the Mini-Mental State Examination (MMSE). The analytical sample comprised 3852 individuals (46% female) aged 65–96 years. During follow-up, growth mixture modeling identified three MMSE score trajectories. Trajectory 1 (4.8% of participants) was characterized by a steep decline, Trajectory 2 (22.1% of participants) by a gradual decrease, and Trajectory 3 (73.1% of participants) by high scores that remained nearly stable throughout the follow-up period. Overall, 540 participants (14.1%) had undernutrition, with a prevalence significantly higher in Trajectory 1 (26.9%) than in Trajectory 2 (17.3%) or Trajectory 3 (12.2%). Baseline undernutrition was associated with a higher probability of belonging to the rapidly decreasing Trajectory 1 (OR=1.71, 95% CI 1.06-2.77; reference: Trajectory 3); a finding driven mainly by the phenotypic GLIM criteria. Undernutrition is associated with steeper cognitive decline in older adults, particularly when phenotypic signs are present. However, given the potential bidirectional relationship between cognitive status and undernutrition, reverse causation cannot be ruled out entirely. Nevertheless, our findings underscore the importance of assessing nutritional status in advanced age, as it represents a modifiable factor that may delay or prevent cognitive decline.