Associations of serum carotene levels and decline for the ability of attention: a longitudinal study in the Japanese general population

Background: Although serum carotene may contribute to dementia prevention, there is a lack of longitudinal evidence for early cognitive decline before dementia symptoms. The aim of this study was to examine whether serum carotene levels were associated with annually evaluated cognitive trajectories among the Japanese general population. Methods: Among 581 baseline participants, 199 individuals (83 males; mean age [min, max], 62.7 [39, 90] years) who underwent cognitive assessments more than twice after baseline were analyzed. “Attention” levels were assessed using one-and three-target Digit Cancellation Tests (D-CAT1 and D-CAT3). “General cognitive ability” was assessed by the short version of Mini-Mental State Examination (SMMSE). Serum carotenes (¡-carotene, ¢-carotene and lycopene) were measured by high-performance liquid chromatography. After the measurements, we calculated total carotene levels by summing up the levels of all measured carotene. Carotene levels were categorized into three groups for analysis (low: 0%–25%, middle: 25%–75%, and high: 75%–100%). A linear mixed model was used to estimate the slope of the D-CAT score trajectory and to compare it between three categories. Results: Compared with the middle carotene group, decline of attention was faster in the D-CAT1 for low ¢-carotene (¢ = ¹3.48, p = 0.035), lycopene (¢ = ¹3.10, p = 0.062), and total carotene (¢ = ¹4.75, p = 0.003), but not for ¡-carotene (¢ = ¹2.60, p = 0.111). For the D-CAT3, decline of attention was faster in the group of low lycopene (¢ = ¹3.17, p = 0.002) and total carotene (¢ = ¹2.17, p = 0.037) compared with the middle carotene group, while no clear association for ¡-carotene (¢ = ¹0.67, p = 0.521) and ¢-carotene (¢ = ¹0.64, p = 0.639). There were no clear associations between serum carotene and the SMMSE score. Conclusions: These findings suggest low levels of serum lycopene are associated with a decline of attention in the setting of the general population.