Smoking status and the electrocardiogram: a cross-sectional and longitudinal study.

Previous cross-sectional studies have shown age trends in electrocardiographic wave patterns, including leftward shift in frontal plane axis and decreases in R, S, and T wave amplitudes with age. The effects of smoking on electrocardiographic measurements have also been examined. Findings of several studies vary and include possible smoking-induced changes in T wave amplitude and frontal plane axis measurements. To examine both cross-sectionally and longitudinally the effects of cigarette smoking on electrocardiographic measurements, serial recordings obtained 5 yr apart were taken from 702 healthy male participants of the Normative Aging Study, who were 23-74 yr of age at their first examination. These men were classified as current smokers (at both baseline and follow-up examinations, N = 291), former smokers (men who stopped smoking prior to the baseline examination, N = 203), or never smokers (at any time, N = 208). At baseline, P-R interval duration was shorter in current smokers than in former or never smokers. Longitudinal results indicated that R, S, and T wave amplitudes decreased at greater rates in smokers than in nonsmokers. These findings suggest that changes in the electrocardiogram attributed to aging may be modified by smoking.