The relationship of hostility, negative affect and ethnicity to cardiovascular responses: an ambulatory study in Singapore Hwee Chong Enkelmann a , George D. Bishop a, * , Eddie M.W. Tong a , Siew Maan Diong a , Yong Peng Why a , Majeed Khader b , Jansen Ang b a Department of Social Work and Psychology, National University of Singapore, 11 Law Link, Singapore 117570, Singapore b Police Psychological Unit, New Phoenix Park, 28 Irrawaddy Road, Singapore 329560, Singapore Received 8 June 2004; received in revised form 3 August 2004; accepted 9 December 2004 Available online 12 January 2005 Abstract This study tested the hypotheses that ambulatory heart rate and blood pressure would be higher for individuals high but not low in hostility when they experienced negative affect or social stress and that this interaction would be stronger for Indians compared with other Singapore ethnic groups. Ambulatory blood pressure monitoring was done on 108 male Singapore patrol officers as they went about their daily duties. After each BP measurement participants completed a computerized questionnaire including items on emotional experience. Individuals high in hostility showed higher systolic blood pressure when reporting negative affect whereas this was not true for those low in hostility. Ethnic differences were obtained such that Indians showed an increase in mean arterial pressure when angered whereas MAP was negatively related to anger for Malays and unrelated for Chinese. Also a three-way interaction between ethnicity, hostility, and social stress indicated that hostility and social stress interacted in their effects on DBP for Indian participants but not for Chinese or Malays. Finally, a three-way interaction was obtained between ethnicity, hostility and negative affect for heart rate in which heart rate increased with increasing levels of negative affect for Chinese high in hostility and Malays low in hostility but decreased with increasing negative affect for all other participants. These data are consistent with higher CHD rates among individuals high in hostility and also provide additional evidence on ethnic differences in cardiovascular reactivity in Singapore. D 2004 Elsevier B.V. All rights reserved. Keywords: Ambulatory monitoring; Cardiovascular responses; Emotion; Hostility; Ethnic differences; Singapore 0167-8760/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpsycho.2004.12.003 * Corresponding author. Department of Social Work and Psychology, National University of Singapore, 11 Law Link, Singapore 117570. Tel.: +65 6874 6415; fax: +65 6778 1213. E-mail address: swkgb@nus.edu.sg (G.D. Bishop). International Journal of Psychophysiology 56 (2005) 185 – 197 www.elsevier.com/locate/ijpsycho