Blood pressure and smoking: observations on a national cohort.

The reasons why adult smokers have lower blood pressure than non-smokers have not been determined. It is possible that low blood pressure might precede the onset of smoking. This study investigates this hypothesis in a national cohort study in Britain. Blood pressures and pulse rates taken on a sample of 5019 members of the British Birth Cohort Study (BCS 70) at the age of 10 years were analysed in relation to self reported smoking behaviour at age 16+ years. Prospectively, those children who had lower diastolic blood pressure or pulse rate at age 10 were more likely to have smoked by age 16+ years. Using analysis of variance, pulse rate was significantly related to smoking in young men (p < 0.001). Seventy per cent of those with lower pulse (below the 10th centile), 58% with medium pulse, and 52% with the higher pulse (above the 90th centile) had ever smoked by age 16+ years. In young women, pulse rate (p = 0.003), diastolic pressure (p = 0.024), and systolic pressure (p = 0.032) at age 10 were all significantly related to smoking at age 16. This longitudinal study found that lower blood pressure and slower pulse rate were related to the onset of smoking in children. More research is needed on this new observation.