SMOKING EFFECTS ON DIURNAL-VARIATIONS OF CARDIOVASCULAR PARAMETERS

Previous studies have reported that nicotine increases heart rate and blood pressure, showing a peak 10 min after intake. But most of the wo rk has focused on the period of maximum effect on cardiovascular param eters and has been limited to morning measurements, The aim of this st udy is to evaluate the effects of smoking in diurnal variations of hea rt rate and blood pressure, when no restrictions are placed on the pat tern of consumption and activity is controlled. The sample consisted o f healthy subjects, 21 smokers and 21 non-smokers, from 18 to 26 years . The recordings were carried out hourly from 8:00 to 21:00 h in resti ng conditions. Heart rate was measured beat-to-beat for 2 min, and blo od pressure was assessed by a conventional electronic monitor. Smokers and non-smokers did not differ in diurnal levels of heart rate nor bl ood pressure when time of day was not considered. However, when time o f day was taken into account, the groups differed significantly for he art rate and systolic blood pressure, while diastolic blood pressure o nly showed differences for post-lunch period. The influence of nicotin e on the cardiovascular system of young and healthy smokers is more ap parent in the diurnal variations than in the mean level of heart rate and blood pressure. The results emphasize the importance of a chronobi ological approach in the study of the early stages of smoking on cardi ovascular parameters.