Autonomic nervous system function in women with irritable bowel syndrome

Autonomic nervous system (ANS) balance was assessed in women with and witho ut irritable bowel syndrome (IBS) using laboratory tests of function (ie, e xpiratory/inspiratory ratio, Valsalva, posture changes, and cold presser) a nd spectral and nonspectral measures of heart rate variability (HRV). Women with (N = 103) and without IBS (N = 49) were recruited, interviewed, then completed a laboratory assessment and wore a 24-hr Holter monitor Analysis using the entire sample showed little difference between IBS and control wo men and between subgroups with IBS on either laboratory measures or 24-hr H RV measures. However, analysis restricted to those women with severe IBS sy mptoms showed quite pronounced differences between two IBS subgroups on 24- hr HRV measures. Parasympathetic tone was significantly lower and ANS balan ce was significantly higher in the constipation-predominant compared to the diarrhea-predominant group. Subgroups of women with IBS do differ in ANS f unction as measured by 24-hr HRV; however, these differences are only appar ent among women with severe symptoms. These findings point out the importan ce of considering symptom severity when interpreting studies of IBS.