3.1 The basic characteristics of study population and meteorological factors
After the correction, we observed associations between meteorological factors in different months and seasons and hospital visits for AF patients. Among the AF patients with ST-T changes, a higher proportion was female (62.42%). Furthermore, the AF patients with ST-T changes tended to be older compared to those without ST-T changes (Table 1). The distribution of AF cases with ST-T segment changes across days, months, and seasons is illustrated in Fig. 2 and Fig. 3.
In 2015, the months with the lowest number of AF cases were June (5.68%) and November (6.33%). Similarly, in 2016, AF incidence was lowest in May (6.37%) and September (7.07%). In 2017, the months with the lowest number of AF cases were June (6.83%) and July (6.38%). Finally, in 2018, the lowest number of AF cases occurred in July (6.64%) and September (5.59%) (Fig. 3).
3.2 The relationship of meteorological factors and the air pollution
Due to the observed correlation between air pollutants and meteorological factors, necessary corrections were applied to the data analysis. As outlined in the Supplementary Table, measurements were taken for particulate matter, gaseous air pollutants, and various meteorological variables. The analysis was adjusted using the data from air pollutant measurements to more accurately determine the impact of meteorological factors on hospital visits by patients with AF.
For the period from January to December 2015–2018, Spearman's Rho-related technology was utilized to examine the correlation between meteorological variables and air pollutants (Supplementary Table). The results of Spearman's rho correlation indicated positive associations among various air pollutants. With the exception of average temperature, average relative humidity, and average wind speed, which showed no significant correlation with the number of AF patients, all other factors were found to be related. This correlation analysis revealed a significant relationship between meteorological factors and air pollution, with further details provided in the Supplementary Table.
Please refer to the Supplementary Table for comprehensive information on the correlations among meteorological variables and air pollutants.
3.3 Less AFs occurred in the third quarter
Based on the analysis of the data in Fig. 2, the time-series chart depicts the changing trends of meteorological variables over time. Most of the meteorological factors display distinct periodic variations, and the overall trends remain relatively stable. Notably, temperature and air pressure exhibit evident seasonal patterns. The variations in hospital visits for AF patients across different quarters are likely influenced by these meteorological factors.
Upon analyzing the data from Figs. 2 and 3, we observed a significant seasonal fluctuation in the number of AF patients visiting the hospital (P < 0.05). The lowest mean number of events was recorded in the third quarter compared to the other quarters (569 ± 54.75). Conversely, the first quarter showed the highest number of AF cases (744 ± 57.10).
3.4. Partial meteorological factors have relationship with the hospital visits of the AFs
The lag analysis method was used to explore the correlation between meteorological factors and AF occurrence, taking into account the lag effect on PM [24]. Conditional logistic regression (R software "season" package) was applied to analyze the effects of various lag periods of average atmospheric pressure, average temperature, average relative humidity, average wind speed, daily atmospheric pressure range, and daily atmospheric temperature range on daily AF cases, while correcting for pollutants (PM2.5, PM10, O3, SO2, NO2, and CO).
Upon correcting the relevant pollutant data (PM2.5 daily mean, PM10 mean, O3-day maximum 8-hour mean, SO2 mean, NO2 mean, CO daily mean), the results revealed that average atmospheric pressure and average temperature were protective factors (lag 0: OR 0.9901, 95% CI 0.9825–0.9977, P < 0.05, and lag 1: OR 0.9890, 95% CI 0.9789–0.9992, P < 0.05) (Fig. 4AB). Conversely, a statistically significant correlation was observed between AF with constant ST-T segment and average atmospheric pressure 7 days before the event (lag 7: OR 1.0136, 95% CI 1.0027–1.0246, P < 0.05) (Fig. 5A). This indicates that average atmospheric pressure acts as a risk factor for AF patients with ST-T changes, while no significant correlation was found between AF with ST-T segment changes and average atmospheric pressure.
The analysis further revealed a statistically significant correlation between daily pressure range and AF events, with the association fluctuating over time. Initially, it acted as a protective factor (lag 0: 95% CI 0.9684–0.9913, P < 0.01) (Fig. 4E), but became a risk factor after 7 days (lag 7: OR 1.019, 95% CI 1.0079–1.0312, P < 0.01) (Fig. 4E). In subgroup analysis, the daily pressure range was a risk factor for patients with no ST-T segment change (lag 2: OR 1.0172, 95% CI 1.0009–1.0337, P < 0.05), while AF with ST-T changes exhibited positive correlations with daily pressure range at various lag periods (lag 0: OR 0.9734, 95% CI 0.9592–0.9878, P < 0.01; lag 3: OR 1.0162, 95% CI 1.0021–1.0306, P < 0.05; lag 7: OR 1.0211, 95% CI, P < 0.05) (Fig. 5E), indicating heightened vulnerability. Hence, daily atmospheric pressure range is considered a risk factor for AF events.
Moreover, daily atmospheric temperature range was identified as a risk factor (lag 5: OR 1.0208, 95% CI 1.0087–1.0331, P < 0.01) (Fig. 4F). In the subgroup analysis, patients with no ST-T segment changes also showed a correlation with daily temperature range (lag 5: OR 1.0181, 95% CI 1.0013–1.0351, P < 0.05), while patients with ST-T changes displayed a more pronounced correlation (lag 5: OR 1.0244, 95% CI 1.0069–1.0422, P < 0.01) (Fig. 5F), indicating increased vulnerability. Conversely, no significant differences were found between average relative humidity, average wind speed, and AF events (Fig. 4CD).
In contrast to previous literature, this study divided the population into subgroups based on ECG ST-T segment changes, an aspect not previously explored. In the subgroup analysis, for patients with no ST-T segment changes, only average atmospheric pressure displayed an influencing lag factor, while for patients with ST-T segment changes, the lag factor aligned with the overall correlation. This subgroup analysis suggests that patients with ST-T segment changes are more susceptible to daily atmospheric pressure range and daily atmospheric temperature range. For further data display, the relationship between meteorological factors and uncorrected pollutants' effects on AF was analyzed and can be found in the attachment (Supplementary Fig. 1, 2).