“Broken” autonomic cardiac circadian clock in obese adolescents: evidence and implications

Excerpt

In the present issue of Clinical Autonomic Research, Rodriguez-Colon et al. [1] examine the behavior of 24-h heart rate profile in a large cohort of adolescents recruited in the follow-up of the Penn State Children Cohort Study. Specifically, the authors performed power spectral analysis of the 24-h heart rate signal in order to determine whether and to what extent the high-frequency/low-frequency components of the R–R interval, which are well known to represent reliable indices of parasympathetic/sympathetic cardiac drive, respectively [2], are altered in these subjects. Data that were analyzed by adjustments for confounders (specifically age and gender) were compared to those obtained in non-obese children and adolescents. The results expand previous information collected on this topic [3‐6], by showing that the circadian pattern of parasympathetic and sympathetic control of the heart rate signal is altered in these young groups of obese. They also provide evidence that the alterations in vagal modulation of sinus node activity are manifest in both genders, independently of the subject’s age and over the whole 24-h period. However, when circadian curves of estimated high-frequency components detected in obese and control subjects are compared, it becomes clear that the difference in the two curves is greater for magnitude in the daytime period between 6.00 a.m. and 2.00 p.m. This time window includes the early morning hours known to be associated with a pronounced adrenergic overdrive to the heart and peripheral vessels, and with a greater risk of sudden arrhythmic death, particularly in obese patients [2, 7]. …