Over the last few decades, heart rate variability (HRV) has been used to estimate the balance between the sympathetic and the parasympathetic nervous system in healthy and diseased humans. There exists very little data on the effect of different ethnic groups on short term heart rate variability. The aim of our study was to investigate the extent to which ethnicity affects 5 minute heart rate variability recordings in healthy humans. A secondary aim was to assess other factors that could influence HRV in these subjects, such as resting blood pressure, levels of exercise, alcohol or smoking intake. Previous data collected in our lab was compiled and analysed. In total, HRV data from 264 healthy subjects was analysed. Most subjects were staff and students of Plymouth University (PU). Previous studies were given ethical approval by the Research Ethics committee, PU. All participating subjects gave informed and signed consent. An ECG lead was attached to each limb. LabChart software and a PowerLab were used for data acquisition. Subjects were supine and underwent one standard five minute HRV measurement. Data was also normalised by taking into account the heart rate [1]. Short term HRV was assessed using time domain (HR, SDNN), frequency domain (LFnu and HFnu alongside normalised LFnu and HFnu) and Poincaré analysis (SD1 and SD2). Different ethnic groups were investigated (Arab, Asian, Black, South Asian and White). Mixed subjects were excluded. Analysis was across all five ethnicities, and then both Asian and South Asian subjects were combined, to allow for analysis to be made across four ethnicities. The results were analysed by one way ANOVA. P < 0.05 was considered as significant. The subjects’ mean (± S.D.) age was 25.8 ± 10.0 years and mean BMI was 24.9 ± 5.2 kg m-2. Ethnic details of the 264 healthy subjects are shown in Table 1 below. Ethnic group Subject numbers Arab 74 Asians 25 Black 23 Mixed 4 South Asians 31 White 107 Table 1. Subject numbers of each ethnic group in the study (n=264). HR (p=0.286) and SDNN (p=0.333) were not different across all five ethnicities. With four ethnic groups, HR (p=298) and SDNN (p=0.206) again did not show any differences. LFnu was significantly different across all five groups (p=0.001), while HFnu was not (p=0.348). Pairwise comparison showed Blacks (35.83 Hz) had a lower LFnu than Whites (52.55 Hz; p=0.002). With four ethnic groups, a similar significant difference was noted in LFnu, with Blacks having a lower value than Whites. Normalised LFnu was also significantly higher in Whites than Blacks, across both four and five ethnic group analysis. LFnu is an indicator for sympathetic response while HFnu is an indicator of parasympathetic response. Therefore, it seems our White participants had a greater sympathetic (fight or flight) response, relative to an attenuated response in Black participants. Further research is needed to elucidate possible reasons for these differences in frequency domain HRV variables across ethnic groups.