1988 Volume 25 Issue 4 Pages 408-412
The circadian rhythm of heart rate was assessed using 24 hour electrocardiographic recordings in 88 hospitalized elderly patinets without any organic heart diseases. To investigate the factors influencing the diurnal variation of heart rate, patients were classified on the basis of dementia and physical disability into four groups. To determine if heart rate fluctuates rhythmically with a circadian period, mean hourly heart rate in 24 hour electrocardiographic recordings was used to fit cosine curves by the statistical technique of least squares, and three parameters of the rhythm -designated the mesor, amplitude, and acrophase- were estimated. 1) The cosine curves were fitted with a P value of 0.001 or less in all patients. 2) The mesor represented the rhythm-adjusted mean of heart rate. An analysis of the mesor revealed no significant difference in each group. 3) The amplitude values were derived from one half of the total diurnal variation of heart rate. The amplitude was significantly larger in patients without physical disability than in those with physical disability, regardless of accompanying dementia. This finding is a probable result of diminished autonomic nervous system activity, especially sympathetic nervous system activity in patients with physical disability. 4) The acrophase indicated the time when heart rates were at their peak above the mean. The acrophase showed a significant delay in patients with dementia, compared with that of patients without dementia. This result suggests that impaired central autonomic nervous system which regulates the acrophase of periodicity is present in patients with dementia.
