Cigarette smoking acutely elevates sympathetic activity and blood pressure (Sleight, 1993; Narkiewicz et al. 1998), but it is not known whether smokers have chronically increased blood pressures or exhibit changed responsiveness to reflex stimuli that cause sympathetic activation. We have therefore compared cardiovascular responses to three mental stress tests in young (20-22 years) men who were smokers with a self-reported habit of at least 10 cigarettes per day for 2 years or life-long non-smokers (n = 10 each group).

All measurements were made between 09.00 and 12.00 h and participants were instructed to refrain from smoking, alcohol and caffeine-containing beverages for 12 h beforehand. Parameters measured were beat-to-beat blood pressure by applanation tonometry, heart rate by ECG and stroke volume by impedence cardiography. The tests employed were mental arithmetic, mirror drawing and reflex colour discrimination and all procedures had institutional ethics approval. Significance of differences (P < 0.05) was assessed by Student’s t test for paired comparisons and Welch’s test for unpaired comparisons.

At rest, smokers had higher mean blood pressures than non-smokers (97 ± 3 cf. 83 ± 2 mmHg, means ± S.E.M.) and the absolute pressures were proportional to self-reported cigarette consumption. Resting heart rates and cardiac outputs were similar between groups (71 ± 3 cf. 74 ± 3 b.p.m., 4.7 ± 0.2 cf. 4.8 ± 0.4 l min^-1). Each test elevated mean blood pressures in both groups (peak values smokers cf. non-smokers: 123 ± 10 cf. 100 ± 6 (arithmetic), 112 ± 9 cf. 94 ± 4 (mirror drawing), 110 ± 7 cf. 105 ± 4 (colour discrimination)). In non-smokers, mental arithmetic increased heart rate (peak 92 ± 5 b.p.m.) and cardiac output (peak 6.6 ± 0.6 l min^-1), but stroke volume was not altered; the other tests affected neither heart rate nor cardiac output. In smokers, by contrast, heart rate and cardiac output were elevated in response to each test (peaks 92 ± 5 b.p.m., 7.0 ± 0.6 l min^-1 (arithmetic); 79 ± 3 b.p.m., 5.7 ± 0.3 l min^-1 (mirror drawing); 79 ± 3 b.p.m., 6.0 ± 0.3 l min^-1 (colour discrimination)) and mental arithmetic also increased stroke volume from 68 ± 4 to 81 ± 4 ml.

Our results support the view that chronic smoking causes an elevation of resting blood pressure that is not restricted to the immediate smoking period. Smokers also exhibit elevated cardiac workload during cerebral arousal, which may contribute to the smoking-associated risk of myocardial infarction.