Previous studies have found an association between serum albumin levels and cognitive function. However, the results of this association are inconsistent, and the effect of Apolipoprotein E (APOE) on the association is less clear. Using retrospective cohort data (2008-2020), we investigated whether chronic serum albumin was associated with cognitive performance in older adults. We further assessed how the APOE genotype modifies its relevance. A total of 2396 Korean veterans and their families who were aged 65 years or older in 2008 and who had both data of serum albumin and cognitive performance (assessed by the Mini-Mental State Examination, MMSE) were included for the current study. The serum albumin levels were divided into four groups by quartiles: Group 1 (<4.0 g/dL), Group 2 (4.0-4.19 g/dL), Group 3 (4.2-4.49 g/dL), and Group 4 (≥4.5 g/dL). APOE ε4 carriers were defined as the presence of at least one ε4 allele (ε2/4, ε3/4, ε4/4). After adjusting for age, sex, and medical conditions, serum albumin levels (assessed by the median serum albumin levels during the study period) were significantly associated with increases in the median MMSE scores (beta = 3.30, p < 0.0001). Compared with the lowest median albumin category (Group 1), the beta coefficients for the median MMSE score were significantly and gradually increased in Group 2 (beta = 2.80, p < 0.0001), Group 3 (beta = 3.71, p < 0.0001), and Group 4 (beta = 4.01, p < 0.0001), respectively. In the analysis of repeated albumin measures, similar patterns were observed in cognitive function. All regression coefficients were greater in ε4 carriers than in non-carriers. Our findings suggested that sustained lower serum albumin levels were associated with lower MMSE scores. This observation may be modified by APOE polymorphisms.
Keywords: APOE; albumin; cognition; risk factor.