CIRCADIAN AND ULTRADIAN RHYTHMS IN HEART-RATE AND MOTOR-ACTIVITY OF SMOKERS, ABSTINENT SMOKERS, AND NONSMOKERS

In a field study, heart rate and motor activity were assessed continuo usly in 12 male smokers during 2 smoking and 2 abstinence days and in 12 male nonsmokers during 4 days. A circadian analysis revealed earlie r activity acrophases in smokers than nonsmokers and earlier heart rat e acrophases in abstinent than smoking smokers. Furthermore, heart rat e acrophases of smoking smokers significantly anticipated activity acr ophases, whereas in abstinent smokers and nonsmokers the two parameter s oscillated in phase. With the use, in smoking smokers, of the indivi dual average smoking interval as a hypothetical ultradian period lengt h, significant periodicities were found for heart rates in 16 and for activity in 15 of 24 observation days. These rhythms were nicotine ind ependent and based on heart rate and activity increases prior to light ing up the cigarettes. Individual frequency spectra for the 16 h after getting up and the 7 h after going to bed did not reveal single domin ant frequencies but rather complex frequency distributions. Power spec tra of the daytime data revealed no group differences for activity and no heart rate differences between smoking smokers and nonsmokers. In abstinent smokers, however, a significant reduction of heart rate freq uencies slower than 1 cycle/135 min and a significant increase of hear t rate frequencies faster than 1 cycle/20 min were observed as compare d with all other groups. This effect persisted over the 2 abstinence d ays, suggesting an activity-independent change in the frequency distri bution of heart rates after quitting smoking.