Total caffeine intake is associated with lower serum α-Klotho and may impact its detection accuracy: Evidence from...

The relationship between total caffeine intake (TCI) and aging remains understudied. α-Klotho (KL), a key aging-related circulating biomarker, is clinically valuable. Unlike prior studies focusing on coffee intake, we analyzed TCI (from diet and supplements) to isolate its independent association with KL and explore mechanisms via molecular docking. We thus conducted a cross-sectional analysis with NHANES 2007 to 2016 data to investigate TCI and serum KL levels in adults aged 40 to 79. Serum KL levels were determined using ELISA kits, while trained interviewers assessed TCI through 24-hour dietary recalls. Generalized linear regression models were employed to evaluate the correlation between TCI and serum KL levels. We utilized restricted cubic spline analysis to explore the dose-response relationship between the 2 factors. Subgroup analyses and molecular docking studies were also conducted to further understand the association. After adjusting for potential confounders, higher TCI was significantly associated with lower serum KL levels. In the fully adjusted model, compared to the lowest TCI group, KL levels decreased by -30.21 pg/mL (95% CI = -50.49 to -9.93 pg/mL) and -27.31 pg/mL (95% CI = -51.94 to -2.67 pg/mL) in the third and fourth groups, respectively, indicating a significant trend (P for trend = .005). Restricted cubic spline analysis revealed a linear dose-response relationship (P for nonlinearity = .362). Subgroup analyses showed that the negative correlation was more pronounced in participants aged < 60 years, those who were overweight/obese, and females. Molecular docking analysis suggested a direct interaction between caffeine and KL, with a binding energy of -5.299 kcal/mol, implying a stable interaction. These results suggest a potential pro-aging effect of caffeine. Further prospective studies and experimental validation are needed to clarify caffeine's effects on KL. Notably, molecular docking indicates caffeine may interfere with α-Klotho immunoassay detection, emphasizing the need for caffeine abstinence before testing to enhance biomarker accuracy.