Abstract / Summary
Dementia prevalence is increasing worldwide, with Alzheimer’s disease (AD) being the most common type. Amyloid-beta (Aβ) aggregation is an early pathological event in AD. Although carotenoids have been shown in vitro to inhibit Aβ aggregation through antioxidant and anti-inflammatory effects, human evidence remains limited. Recently, blood-based biomarkers such as Aβ42/40 ratios, phosphorylated tau (p-tau181, p-tau217), and neurofilament light chain (NfL) have enabled assessment of AD-related pathology. We analyzed 770 participants from the 2024 Iwaki Health Promotion Project in Japan. The associations between circulating carotenoid levels (skin and blood) and blood AD-related biomarkers were examined using adjusted linear and nonlinear regression models in a cross-sectional design. Among participants under 60 years, those in the highest quartile of skin carotenoid levels had significantly higher Aβ42/40 ratios than those in the lowest quartile (β = 0.0024, 95% CI: 0.0003–0.0046). The magnitude of the association was comparable to the cross-sectional difference in Aβ42/40 ratio observed across approximately 4–8 years of age. Among the blood carotenoids measured, lutein and α-carotene were positively associated with Aβ42/40 ratios. In summary, higher circulating carotenoid levels were associated with more favorable Aβ profiles in individuals under 60 years.