Do nicotine intake and acute heart rate response to smoking rank nicotine dependence the same?

In this study, two proposed scales of nicotine dependence were compared: self-administered nicotine intake and acute heart rate sensitivity to smoking. Our aim was to determine if these nicotine dependence scales would rank relative dependence the same in a sample of 15 male chronic smokers who smoked their first cigarette in the morning after overnight abstinence. Heart rate and plasma nicotine levels were measured before and 5, 10, 15, and 30 min after smoking. The results of this pilot study suggest that heart rate sensitivity and nicotine intake do not have a direct linear relationship, but rather a curvilinear relationship. A marked increase in heart rate sensitivity was observed at approximately the 70th percentile of nicotine intake.