Influence of smoking on baroreceptor function: 24 h measurements

Recent studies showed that smoking four cigarettes per hour impairs baroreflex sensitivity in humans. In this study, baroreceptor function was qualified more precisely by 24 h measurements using the new portable Portapres system, allowing a continuous non-invasive registration of blood pressure curves.

Twenty-four smoking individuals (12 male/12 female) who smoked more than 10 cigarettes per day for more than 6 years were investigated. Thirty non-smokers (15 male/15 female) served as controls. Data were evaluated separately for the 08:00-22:00 h and 22:00-08:00 h periods.

Within one 24 h period, smokers showed a higher blood pressure [female: mean arterial blood pressure (MAP) 85.5 mmHg; male: MAP 93 mmHg] compared to non-smokers (female: MAP 80 mmHg; male: MAP 90 mmHg). During daytime (08:00-22:00 h), this difference reached a level of statistical significance (P< 0.05) in female subjects. Heart rate was significantly higher in smokers (female: 86 bpm; male: 80 bpm) compared to non-smokers (female: 77 bpm; male: 70 bpm) during the 24 h observation period. The number of sequences (seq) in smokers surpassed the number of sequences in non-smokers by about 53 seq/day, which corresponds to a significant difference of 4.5%. At night the sympathetic -systolic blood pressure/-pulse interval (-SBP/-PI) sequences of the smoking group predominated over the -SBP/-PI sequences in the non-smoking group. On the other hand, the parasympathetic +SBP/+PI sequences were significantly less in smokers between 22:00 and 08:00 h. The regressions (i.e. D pulse interval/D SBP [ms/mmHg]), which represent the baroreceptor sensitivity, were clearly smaller in smokers.

The present study provides evidence that chronic tobacco (nicotine) abuse causes pathological alterations of autonomic nervous blood pressure regulation which can be measured under normal living conditions and may be described as sympathovagal dysbalance and decreased baroreceptor sensitivity. Taken together with processes such as elevated catecholamine blood levels, these alterations may explain the higher risk of cardiovascular diseases.