Diurnal variations in arousal: a naturalistic heart rate study in children with ADHD

Abstract

Previous studies suggest an altered circadian regulation of arousal in children with Attention-Deficit Hyperactivity Disorder (ADHD) as measured by activity, circadian preference, and sleep-wake patterns.Although heart rate is an important measure to evaluate arousal profiles, to date it is unknown whether 24-hour heart rate patterns differentiate between children with and without ADHD.In this study, 24-hour heart rate data were collected in 30 non-medicated children with ADHD (aged 6-11) and 30 sex-, class-, and age-matched normal controls in their naturalistic home and school setting, during five days. Simultaneously, 24-hour activity patterns were registered. Confounding effects of demographic variables (e.g., age, sex, BMI, pubertal stage) and comorbid internalizing and externalizing problems on heart rate levels were additionally assessed.Longitudinal analysis showed that heart rate levels were overall higher in the ADHD group (p<0.01) -with largest effects during afternoon and night-, in a model controlling for age. Other factors did not significantly contribute to variations in heart rate levels. Compared to controls, children with ADHD showed higher activity levels during daytime (especially early afternoon), but not during nighttime (p<0.05). Post hoc analyses showed that environmental effects may influence daytime variations.Findings suggest an autonomic imbalance in children with ADHD as compared to controls, with higher heart rate levels in the ADHD group. Nighttime tachycardia in this group could not be explained by nighttime activity levels or comorbid externalizing/internalizing problems. Further research on autonomic functioning in ADHD is recommended because of the major impact of higher resting heart rate on health outcomes.

Heart Rate Variability: An Index of the Brain-Heart Interaction

“…Interestingly, the other study revealed tachycardia in children with ADHD in comparison with controls; importantly, this tachycardia was observed during day and night. Nocturnal tachycardia in this group could not be explained by nocturnal activity levels or comorbid externalizing/internalizing problems (Imeraj et al, 2011). These conclusions are consistent with our findings of tachycardia in the children suffering from ADHD-combined type (Tonhajzerova et al, 2009a).…”

Altered circadian profiles in attention-deficit/hyperactivity disorder: An integrative review and theoretical framework for future studies

“…As hyperactivity in the ADHD group was only obvious during daytime and not during nighttime periods, the authors suggested that -along with contextual factors-circadian rhythms might play a role in these differential activity patterns. Similar findings were obtained in a larger sample by Imeraj et al (2011). Moreover, their finding of higher daytime activity levelsespecially during noon and early afternoon hours-confirmed an important role for time of day effects in addition to environmental conditions in the expression of (afternoon) problem behavior in ADHD.…”

Cardiovascular Safety of Stimulants in Children with Attention-Deficit/Hyperactivity Disorder: A Nationwide Prospective Cohort Study

“…Animal studies have found that stimulants prolong action potential duration and resting membrane potential in sinoatrial cells (Aileru and Carpentier 1996), affect action-potential repolarization in ventricular myocytes (Casis et al 2000), affect cell membranes in the myocardium (Henderson and Fischer 1995), and have dose-related structural effects on capillary endothelial cells (Bahcelioglu et al 2009). Drug-näive children with ADHD have higher heart rates than controls (Huang and Tsai 2011;Imeraj et al 2011;Buchhorn et al 2012a) and reduced heart rate variability (HRV), which is normalized by methylphenidate (Buchhorn et al 2012b).…”