Abstract
We examined the factors related to disappearance of the circadian rhythm of parasympathetic nervous function in asthmatic children. The subjects were 145 children with asthma. All the patients underwent 24-h electrocardiography. We measured the %RR50 for 1h and analyzed the rhythm using the single cosine fitting method. We used the values of the MESOR (the midline-estimating statistic of rhythm), amplitude and acrophase. Circadian rhythm disappeared in 34 (disappearance group) of the patients, and was retained in 111 patients (retained group). Several factors, including age, status, time of asthma attack, severity of asthma, therapy and NNA were compared between the disappearance group and the retained group. The NNA value was lower in the disappearance group than in the retained group (t=2.07, p=0.04). There was no significant difference in other factors between the groups. In some asthmatic children, the circadian rhythm of %RR50 disappeared, and parasympathetic nervous function was poor during remission. It is suggested that increase in heart rate is related to some disorder of biologic rhythm of asthmatic children.
