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

Abstract

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 β 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 (β coefficient –0.081, SE=0.017; P<0.001) than in adults 20 to 44 years old (β coefficient –0.023, SE=0.019; P=0.24) or adults aged 45 to 64 years old (β coefficient 0.024, SE=0.015; P=0.10) (P 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.