Physical activity and telomere length in American Indians: the Strong Heart Study. Author: Fretts AM1, Mete M2, Howard BV3, Best LG4, Siscovick DS5, Eilat-Adar S6, Zhao J7 Affiliation: <sup>1</sup>Department of Epidemiology, Cardiovascular Health Research Unit, University of Washington, 1730 Minor Ave, Suite 1360, Seattle, WA, 98101, USA. amfretts@u.washington.edu. <sup>2</sup>MedStar Health Research Institute, 6525 Belcrest Rd #700, Hyattsville, MD, 20782, USA. <sup>3</sup>Georgetown and Howard Universities Center for Translational Sciences, 4000 Reservoir Road, Washington, DC, 20007, USA. <sup>4</sup>Missouri Breaks Industries Research Inc, 118 South Willow St, Eagle Butte, SD, 57625, USA. <sup>5</sup>New York Academy of Medicine, 1216 5th Ave, New York, NY, 10029, USA. <sup>6</sup>Zinman College for Physical Education and Sports, Wingate Institute, Netanya, Israel. <sup>7</sup>Department of Epidemiology, Division of Genetic Epidemiology, University of Florida, 2004 Mowry Road, PO Box 100231, Gainesville, FL, 32611, USA. Conference/Journal: Eur J Epidemiol. Date published: 2018 Feb 7 Other: Special Notes: doi: 10.1007/s10654-018-0363-2. [Epub ahead of print] , Word Count: 184 Telomere length, a marker of biological aging, has been associated with many chronic diseases, but its relations with physical activity remains unclear. The purpose of this study was to examine the association of objectively measured ambulatory activity with leukocyte telomere length (LTL), a marker of biological aging, among American Indians. This cross-sectional study included 2312 AI participants from the Strong Heart Family Study. Steps per day were measured using Accusplit AE120 pedometers. Quantitative PCR was used to measure LTL. Generalized estimating equations were used to examine the associations of steps per day with LTL. The median steps per day over a 1 week period was 5118 steps (interquartile range = 3163-7576 steps). Compared to participants in the lowest quartile of steps per day, participants in the upper three quartiles of steps per day had longer LTL: beta ± SE = 0.0195 ± 0.0144, 0.0273 ± 0.0139, and 0.0375 ± 0.0143 T/S ratio units longer (p trend = 0.010) after adjustment for potential confounders. These data suggest that ambulatory activity is associated with LTL. Further studies are needed to determine the mechanism by which ambulatory activity influences LTL. KEYWORDS: American Indians; Pedometer; Physical activity; Telomeres PMID: 29417315 DOI: 10.1007/s10654-018-0363-2