This study included 34,965 participants (13,983 men and 20,982 women). The baseline characteristics of the participants are summarized in Table 1. The mean ages of men and women were both 44.8 years old. There were no significant differences comparing the mean age (p = 0.765) and the age classes (p = 0.886) between men and women. Men had significantly higher prevalences of overweight, obesity, presence of smoking history, hypertension, diabetes and presence of one or more CVD risk factors (Table 1).
The weighted prevalences of arrhythmias in men, women and all participants with different ages are summarized in Table 2. Major arrhythmias accounted for 1.70% of all participants. The weighted prevalence of major arrhythmias in men was higher than in women (2.37% vs 1.04% in men vs women) (Table 2). The weighted prevalences of major arrhythmias in the young (20-44 years old), middle (45-59 years old) and older age (≥60 years old) groups were 1.30%, 2.37% and 5.56% in men, and 0.58%, 1.06% and 2.38% in women, respectively. Specifically, atrial fibrillation/flutter (MC 8-3) accounted for 0.28%, 0.35% and 0.20% in the whole population, men and women respectively. Complete RBBB (MC 7-2) had the highest prevalence among all major arrhythmias, with the weighted prevalence of 0.85%, 1.16% and 0.55% in the whole population, men and women respectively. Minor arrhythmias accounted for 9.92% in all participants. In the young, middle and older age groups, the weighted prevalences of minor arrhythmia were 11.05%, 10.82% and 14.26% in men, and 6.58%, 7.85% and 14.17% in women, respectively. Individuals in the older age group had higher prevalences of atrial fibrillation/flutter, complete RBBB and atrial/junctional/ventricular premature beats in both men and women, compared with those in the young age group. In addition, gender had an important impact on some specific types of arrhythmia. Complete LBBB, complete RBBB, nonspecific IVCD, sinus bradycardia, incomplete RBBB and Mobitz type I AV conduction defect were more common in men than in women, while sinus tachycardia was more frequent in women than in men (Table 2).
With respect to other ECG abnormalities except arrhythmias, ST depression and T abnormalities and tall R wave left had higher prevalences than other specific ECG types (Table 3). The ST depression and T abnormalities accounted for 10.96%, 7.54% and 14.32% in the whole population, men and women respectively. Tall R wave left accounted for 4.42%, 5.83% and 3.05% in the whole population, men and women respectively. Participants in the older group had higher prevalences of ST depression and T abnormalities, tall R wave left and left axis deviation compared with those in the young group. Gender also had influence on these ECG abnormalities. Compared with women, men had significantly higher prevalences of Q wave abnormalities, ST elevation, tall R wave left, left axis deviation and right axis deviation. Women had higher prevalences of ST depression and T abnormalities and low voltage compared with men (Table 3).
Figures 1A, 1B, 1C and 1D indicated the odds ratios for the effects of multiple factors on major arrhythmias, minor arrhythmias, ST depression and T abnormalities and tall R wave left, respectively, by multivariate logistic regression analysis. Male gender, older age and living in rural area were positively associated with major arrhythmias. It is worth noting that the likelihood of having major arrhythmias in the 60-year-older group was nearly 4 times higher than that in the reference group (20-44 years old). The odds of having minor arrhythmias were significantly higher in males, the middle age group, the older age group, the smoking group, hypertensive participants, and residents living in rural area. Factors that independently influenced the odds ratios of having ST depression and T abnormalities included female gender, older age, hypertension, overweight, obesity and hypercholesterolemia. In addition, male gender, older age and hypertension significantly increased the odds of having tall R wave left.
To identify the factors that influence each arrhythmia ECG type, multivariate logistic regression analysis was conducted, and the results are displayed in Table 4. Older age (at least 60 years old) significantly increased the odds of having atrial fibrillation/flutter, complete LBBB, complete RBBB, nonspecific IVCD, sinus tachycardia, atrial/junctional/ventricular premature beats and Mobitz Type I AV conduction defect. Smoking was positively associated with supraventricular or ventricular rhythm/tachycardia and incomplete RBBB. Hypertension increased the odds of having sinus tachycardia and Mobitz Type I AV conduction defect. Diabetes, obesity and hypercholesterolemia were not positively associated with any arrhythmia ECG type. Residents living in rural area had higher odds of obtaining complete LBBB, nonspecific IVCD, sinus bradycardia and incomplete RBBB compared to those living in urban areas (Table 4).
Regarding the factors influencing other ECG abnormal types except arrhythmias, the results of multivariate logistic regression analysis are displayed in Table 5. Older age (at least 60 years old) was positively associated with ST depression and T abnormalities, tall R wave left, left/right atrial hypertrophy, left axis deviation and low voltage. Smoking was positively associated with Q wave abnormalities, tall R wave right and low voltage. Hypertension significantly increased the odds of having ST depression and T abnormalities, Q wave abnormalities, tall R wave left and left axis deviation (Table 5). Overweight and obesity were positively associated with ST depression and T abnormalities and left axis deviation (Table 5 and Supplemental table 1). Hypercholesterolemia was positively associated with ST depression and T abnormalities (Table 5).
The weighted prevalences of major arrhythmias in participants with none, one, two and at least three CVD risk factors were 1.19%, 1.76%, 1.95% and 2.17% respectively (Table 6). The presence of CVD risk factors significantly increased the odds of obtaining ST depression and T abnormalities, Q wave abnormalities and tall R wave left, after gender and age were adjusted (Table 6). A history of cardiovascular/cerebrovascular diseases significantly increased the odds of having major arrhythmias, atrial fibrillation/flutter, atrial/junctional/ventricular premature beats, ST depression and T abnormalities, Q wave abnormalities, tall R wave left and left axis deviation, with gender and age adjusted (Table 6). The weighted prevalence of major arrhythmias in participants with a history of cardiovascular/cerebrovascular diseases was as high as 5.72%, while the prevalence in those without the history was only 1.61% (Table 6).