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Electrocardiogram (ECG) outcomes serve as early manifestations of cardiovascular functional or structural changes. While temperature fluctuation has been demonstrated to be a risk factor for cardiovascular diseases, few epidemiological studies have reported its relationship with ECG outcomes. In this study, we employed temperature anomaly (TA) as an innovative indicator of temperature fluctuation to quantify its detrimental impacts on ECG outcomes. A longitudinal study design was conducted using the repeated ECG records of the China National Stroke Screening Survey from 2013 to 2019. Only individuals undergoing at least two ECG tests were included. The daily temperature was assimilated by combining three kinds of data: in situ observations, satellite remote sensing measurements and weather research forecast simulations. We used generalized estimating equations to control for autocorrelation among repeated records and to estimate the association between TA and the risk of ECG abnormalities. We found 6837 events of ECG abnormalities in 47,286 individuals with 102,030 visits. Each unit increment of TA increased the risk of ECG abnormalities [odds ratio (OR) = 1.009, 95% confidence interval (CI): 1.001–1.017] and the risk of myocardial ischemia (OR = 1.061, 95% CI: 1.012–1.111). Hierarchic analyses presented a similar association of TA with both ECG abnormalities (OR = 1.017, 95% CI: 1.008–1.026) and myocardial ischemia (OR = 1.061, 95%CI: 1.011–1.114) in Northern China, but not in Southern China. The exposure-response relationship was estimated as a U-shaped curve centered at the TA value of zero. Sudden warming tended to increase the risk of ECG abnormalities and myocardial ischemia, and sudden cooling tended to increase the risk of atrial fibrillation. All these detrimental effects of TA could be modified by specific individual characteristics. In summary, ambient temperature fluctuation increased the risk of ECG abnormalities. This result indicated that regular ECG tests could be an early-warning measure for monitoring the adverse health effects of temperature fluctuations. • Temperature anomaly (TA) is an innovative index reflecting temperature fluctuations. • Each unit increment of TA increases the risk of ECG abnormalities. • The exposure-response curve is U-shaped which centered at the TA value of zero. • ECG tests can be used to monitor the health effects of temperature fluctuations. [ABSTRACT FROM AUTHOR]

Recently, professionals, such as those from the World Health Organization, have recommended a rigorous standard for nitrogen dioxide (NO 2), a typical urban air pollutant affected by regular traffic emissions, based on its short-term and long-term cardiorespiratory effects. However, the association between middle-term NO 2 exposure and cardiovascular disorders remains unknown. This study was conducted to examine the relationship between NO 2 exposure and its middle-term cardiovascular risks indicated by electrocardiogram (ECG) abnormalities. We included 61,094 subjects (132,249 visits) with repeated ECG observations based on longitudinal data from the China National Stroke Screening Survey (CNSSS). The NO 2 exposure concentration was derived from a predictive model, measured as the monthly average concentration in the 6 months of preceding the ECG measurement. We used the generalized estimation equation to assess the association between NO 2 exposure and ECG abnormalities. For each 10 µg/m3 increase in monthly average NO 2 concentration, the odds ratio of ECG abnormalities was 1.10 (95% confidence interval [CI] 1.09–1.12) after multiple adjustments. Stratified regression analyses of urban and rural residents showed associations between middle-term NO 2 exposure and ECG abnormalities in urban (OR 1.09 [95% CI 1.08–1.11]) and rural residents (OR 1.14 [95% CI 1.10–1.19]). The association was robust within different subpopulations. Associations generally remained statistically significant (OR 1.03 [95% CI 1.02–1.05]) after extra adjustment for PM 2.5. Exposure-response relationship analysis revealed a nearly linear relationship between NO 2 exposure and the risk for ECG abnormalities. Using the variation in ECG signals as a potentially reversible indicator for subclinical risk in cardiovascular systems, our study provides additional evidence on the increased risk posed by middle-term NO 2 exposure. Our study showed that policies controlling for NO 2 concentrations are beneficial to prevent cardiovascular diseases among Chinese adults. • NO 2 exposure increases the risk of ECG abnormalities. • The association between NO 2 exposure and ECG abnormalities was robust. • NO 2 exposure have middle-term effects on health. [ABSTRACT FROM AUTHOR]