Platelet-to-lymphocyte ratio and telomere length in older adults: An inverted U-shaped nonlinear relationship: A nationwide cohort study

This study aimed to investigate the association between the platelet-to-lymphocyte ratio (PLR) Log and telomere length in older adults, focusing on the potential nonlinear relationship within a nationwide cohort. Data were obtained from the National Health and Nutrition Examination Survey 1999 to 2000 and 2001 to 2002 cycles, including 2660 participants aged 60 years and older. PLR Log was calculated as the log-transformed value of PLR, which was further analyzed as both a continuous variable and in quartiles. Mean telomere length (TeloMean) was measured using quantitative PCR. Linear regression, trend tests, smooth curve fitting, and segmented regression were employed to evaluate the relationship between PLR Log and TeloMean, adjusting for potential confounders. Subgroup analyses were conducted to assess variations in associations across age, sex, and other variables. An inverted U-shaped nonlinear relationship was identified between PLR Log and TeloMean. Trend analysis demonstrated a significant trend across quartiles of PLR Log in both the minimally adjusted (P for trend = .021) and fully adjusted models (P for trend = .048). Threshold effect analysis identified a breakpoint at PLR Log = 5.564, where TeloMean significantly increased with PLR Log when below this threshold (β1 = 0.034, 95% CI: 0.012-0.057, P = .003), but decreased when PLR Log exceeded this threshold (β2 = -0.115, 95% CI: -0.221 to -0.009, P = .033). This association was more pronounced in participants aged 66 to 74 years (P for interaction = .005). This study provides new insights into the relationship between systemic inflammation and telomere dynamics in older adults. The observed inverted U-shaped relationship suggests that moderate levels of inflammation may help maintain telomere integrity, possibly through improved immune regulation, while excessive inflammation may accelerate telomere attrition due to increased oxidative stress and impaired DNA repair mechanisms. These findings highlight PLR Log as a potential inflammatory biomarker for aging-related telomere dynamics and emphasize the need for further longitudinal studies to validate these associations.