Association between Body Iron Status and Leukocyte Telomere Length, a Biomarker of Biological Aging, in a Nationally Representative Sample of US Adults

Background Excess iron levels can induce oxidative stress and could therefore affect telomere attrition. However, little is known about the impact of body iron status on telomere length. Objective Our aim was to examine the association between serum ferritin concentrations, an indicator of body iron status, and leukocyte telomere length in US adults. Design We conducted a nationwide, population-based, cross-sectional study. Participants/setting We used data from the National Health and Nutrition Examination Survey (NHANES) 1999-2002. We included 7,336 adults aged 20 years or older who had available data on serum ferritin levels and telomere length. High ferritin levels were defined as a serum ferritin level >200 ng/mL (449.4 pmol/L) in women and >300 ng/mL (674.1 pmol/L) in men. Low ferritin levels were defined as a serum ferritin level <30 ng/mL (67.4 pmol/L). Main outcome measures Leukocyte telomere length was assayed using the quantitative polymerase chain reaction method. Statistical analyses Linear regression with survey weights was performed to estimate the association between serum ferritin levels and telomere length. Results The prevalence of adults with high and low serum ferritin levels was 10.9% and 17.6%, respectively. High ferritin levels were inversely associated with telomere length compared to normal ferritin levels. After adjustment for demographic, socioeconomic and lifestyle factors, body mass index, C-reactive protein, and leukocyte cell type composition, the beta coefficient for log-transformed telomere length was -0.020 (standard error [SE]=0.009; P=0.047). The association was stronger in adults aged 65 years or older (beta coefficient -0.081, SE-0.017; P<0.001) than in adults 20 to 44 years old (beta coefficient -0.023, SE-0.019; P=0.24) or adults aged 45 to 64 years old (beta coefficient 0.024, SE-0.015; P=0.10) (beta for interaction 0.003). Low ferritin levels were not significantly associated with telomere length compared with normal ferritin levels. Conclusions In a US nationally representative population, high body iron status was associated with shorter telomeres, especially in adults aged 65 years or older.