[High levels of high-sensitivity C-reactive protein and impaired autonomic activity in smokers]

We investigated the relationship between high sensitivity C-reactive protein (hs-CRP) activity and autonomic nervous activity using heart rate variability in smokers.

The study consisted of 136 healthy subjects, including 66 smokers (35 women, 31 men; mean age 36 years) and 70 nonsmokers (43 women, 27 men; mean age 34 years). Serum samples were collected from all the subjects. Three-channel, 24-hr Holter monitoring was performed to derive the mean heart rate, standard deviation of normal NN intervals (SDNN), standard deviation of 5-minute mean NN intervals (SDANN), root mean square differences of successive NN intervals (RMSSD), high- (HF) and low- (LF) frequency power components, and the LF/HF ratio.

In smokers, the mean duration of smoking was 13.6+/-8.2 years (range 3 to 45 years), and the mean number of cigarettes consumed per day was 16.3+/-7.1 (range 5 to 40). Smokers exhibited significantly higher mean heart rate, hs-CRP and fibrinogen levels, mean platelet volume, white blood cell count, LF, and LF/HF ratio, with significantly lower SDNN, SDANN, RMSSD, and HF values. In smokers, hs-CRP was correlated with the number of cigarettes consumed per day, duration of smoking, fibrinogen level, mean platelet volume, white blood cell count, LF, and LF/HF ratio, and inversely correlated with HF, SDNN, and SDANN. Even smoking a single cigarette resulted in an acute, 0.07-fold increase in the hs-CRP level (p<0.0001). In linear regression analysis, both the number of cigarettes consumed per day (beta=0.52, p=0.011) and duration of smoking (beta=0.073, p<0.0001) had an independent effect on the hs-CRP level.

Smoking both impairs the sympathovagal balance and increases the hs-CRP activity in otherwise healthy smokers, the combination of which would probably contribute to a higher rate of cardiovascular events.