Heart rate variability can be affected by gender, blood pressure, and insulin resistance

We really read with a great interest the paper by Durakoğlugil et al. (1) entitled “The effect of irritable bowel syndrome on carotid intimamedia thickness, pulse wave velocity, and heart rate variability” published in the September issue of Anatol J Cardiol 2014; 14: 525-30. They purposed to investigate a possible association between irritable bowel syndrome and autonomic dysfunction using heart rate variability (HRV) parameters in their study population. They concluded decreased parasympathetic modulation in patients with constipation-predominant irritable bowel syndrome. One of the best non-invasive methods to evaluate the autonomic dysfunction is to measure HRV, defined as the RR interval variability beat-by-beat, and provide us quantitative data about the autonomic nervous system (2). However, HRV parameters can be affected by various variables, including age, gender, nutrition, obesity, hyperlipidemia, diabetes mellitus, hypothyroidism, heart failure, hypertension, coronary artery disease, chronic obstructive pulmonary disease, renal failure, chronic liver disease, and drugs (2-5). It is well known that there is a relationship between gender and HRV measurements (3). Recently, Hillebrand et al. (5) reported an association between body fat and HRV and concluded that insulin resistance might be a reason for this relationship. In the study by Durakoglugil et al. (1), I think that it would be more helpful to present whether there was no statistically significant difference between the patients and control subjects in terms of gender, blood pressure, and insulin resistance, because the study population included overweight or obese people and the frequency of diabetes mellitus and hypertension is higher in the control group. We believe that the results of the study will be stronger with these additional data and whether irritable bowel syndrome really has an effect on autonomic dysfunction, which predicts survival, can be more comprehensible.