Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCA007

Poster Communications

Do fasting healthy subjects show alterations in heart rate variability?

M. M. Subhan1, K. D. Ali1, F. Benterkia1

1. School of Biomedical Sciences, University of Plymouth, Plymouth, United Kingdom.

Most religions encourage a form of fasting. Fasting has been shown to have multiple health benefits. Two studies have investigated heart rate variability (HRV) during Ramadan fasting, one in healthy subjects [1] and the other in hypertensives [2]. Both showed contradicting results but more importantly, lacked a pre-Ramadan baseline. A change in HRV by Ramadan fasting would interest both clinicians and researchers. The aim of this study was to investigate the effects of Ramadan fasting on heart rate variability (HRV) in healthy subjects. 16 healthy volunteers (all male) underwent three consecutive five-minute HRV measurements over two months. Subjects were all staff and students of the University of Plymouth (UoP). The study was given ethical approval by the Research Ethics committee, UoP. All participating subjects gave informed and signed consent. Anthropometry, blood pressure and HRV were measured. To measure HRV, an ECG lead was attached to each limb. LabChart software and a PowerLab were used for data acquisition. The order of the experiments was: 1 week pre-Ramadan, 3 weeks into the month of Ramadan and 3 weeks after Ramadan ended. Data was also normalised by taking into account the heart rate [3]. The results were analysed by repeated measures ANOVA. p < 0.017 was considered as significant. The subjects' mean (± S.D.) age was 31.88 ± 8.08 years and mean BMI was 24.77 ± 2.89 kg m-2. Except BMI, all normalized and non-normalized time and frequency domain HRV variables showed no significant difference over all three occasions. HF did show a non-significant 30% increase from pre-Ramadan to Ramadan. Heart rate and blood pressure also showed no significant changes over this period. Although BMI significantly decreased in Ramadan relative to pre-Ramadan (p=0.0007), it increased post-Ramadan (p=0.004) similar to pre-Ramadan baseline levels. To our knowledge, this is the first study which has investigated the effects of Ramadan fasting on HRV before, during and after fasting. Our data showed HRV in our subjects was not affected by Ramadan fasting. Despite there being no significant HRV changes, the data showed some consistent trends, such as HF, HFnu, SD1 and normalized HF all increasing during Ramadan fasting. This indicated a possible increase in parasympathetic activity during this time. The reason for such autonomic modulation is unclear. All the HRV data had a high standard deviation, indicating a large inter-subject variation. This along with the small number of subjects would have decreased the statistical power of the study. Although our findings did not show any significant HRV changes, further research is required with a larger sample population to determine if Ramadan fasting affects HRV.

Where applicable, experiments conform with Society ethical requirements