Determinants of Racial/Ethnic Differences in Cardiorespiratory Fitness (from the Dallas Heart Study) Ambarish Pandey, MD a , Bryan D. Park, MD a , Colby Ayers, MS a , Sandeep R. Das, MD, MPH a , Susan Lakoski, MD, MS b , Susan Matulevicius, MD, MSCS a , James A. de Lemos, MD a , and Jarett D. Berry, MD, MS a,c, * Previous studies have demonstrated ethnic/racial differences in cardiorespiratory fitness (CRF). However, the relative contributions of body mass index (BMI), lifestyle behaviors, socioeconomic status (SES), cardiovascular (CV) risk factors, and cardiac function to these differences in CRF are unclear. In this study, we included 2,617 Dallas Heart Study par- ticipants (58.6% women, 48.6% black; 15.7% Hispanic) without CV disease who underwent estimation of CRF using a submaximal exercise test. We constructed multivariable-adjusted linear regression models to determine the association between race/ethnicity and CRF, which was defined as peak oxygen uptake (ml/kg/min). Black participants had the lowest CRF (blacks: 26.3 – 10.2; whites: 29.0 – 9.8; Hispanics: 29.1 – 10.0 ml/kg/min). In multi- variate analysis, both black and Hispanic participants had lower CRF after adjustment for age and gender (blacks: Std b [ L0.15; p value £0.0001, Hispanics: Std b [ L0.05, p value [ 0.01; ref group: whites). However, this association was considerably attenuated for black (Std b [ L0.04, p value [ 0.03) and no longer significant for Hispanic ethnicity (p value [ 0.56) after additional adjustment for BMI, lifestyle factors, SES, and CV risk factors. Additional adjustment for stroke volume did not substantially change the associ- ation between black race/ethnicity and CRF (Std b [ L0.06, p value [ 0.01). In conclusion, BMI, lifestyle, SES, and traditional risk factor burden are important de- terminants of ethnicity-based differences in CRF. Ó 2016 Elsevier Inc. All rights reserved. (Am J Cardiol 2016;118:499e503) Physical activity and high levels of cardiorespiratory fitness (CRF) are strongly associated with lower risk of cardiovascular (CV) disease. 1e3 Previous studies have identified significant race/ethnic differences in CRF, with lower CRF in blacks than whites. 4e6 This difference in CRF may contribute to the higher risk of CV disease (CVD) and associated mortality in blacks as compared with whites. 7 Variation in CRF is associated with differences in age, gender, obesity, left ventricular volume, and physical ac- tivity. However, the explanation for the variation in CRF across race/ethnicities remains poorly understood. Although previous studies have attributed racial/ethnic differences in CRF levels to genetic factors, 4e6,8 the contribution of body mass index (BMI), lifestyle behaviors, socioeconomic status (SES), CV risk factors and measures of cardiac function to these race/ethnic differences are not well understood. Therefore, we sought to characterize the contribution of these factors to the racial/ethnic differences in CRF among participants in the Dallas Heart Study (DHS). Methods The DHS is a longitudinal, multiethnic population-based probability sample of Dallas County residents, with over- sampling of self-reported black participants to ensure approximately 50% of black and non-black participants. Details of the study design and recruitment procedures have been previously described. 9 The original cohort was enrolled from 2000 to 2002, and original participants and their spouses or significant others were invited to participate in phase 2 of the DHS in 2007 to 2009. At the DHS phase 2 examination, each participant completed a detailed staff- administered survey and underwent a health examination that involved measurement of blood pressure, anthropom- etry, blood and urine sample collection, and CRF testing as detailed in the Supplementary Material. The Institutional Review Board of the University of Texas Southwestern Medical Center approved the study. All participants pro- vided written informed consent. For the present study, we included all DHS phase 2 participants without CVD who had available data on self-reported ethnicity/race and base- line CRF levels (Figure 1). a Division of Cardiology, and c Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas; and b Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, Texas. Manuscript received February 17, 2016; revised manuscript received and accepted May 23, 2016. Dr. Berry receives funding from the Dedman Family Scholar in Clinical Care endowment at University of Texas Southwestern Medical Center, Dallas, Texas and 14SFRN20740000 from the American Heart Association prevention network, Dallas, Texas. The corresponding author had full access to all data in the study and had final responsibility for the decision to submit for publication. All authors have read and agreed to the manuscript as written. See page 502 for disclosure information. *Corresponding author: Tel: (þ1) 214-645-7500; fax: (þ1) 214-645- 75201. E-mail address: jarett.berry@utsouthwestern.edu (J.D. Berry). 0002-9149/16/$ - see front matter Ó 2016 Elsevier Inc. All rights reserved. www.ajconline.org http://dx.doi.org/10.1016/j.amjcard.2016.05.043