A circadian variation in the cardiovascular parameters has been detected. It is plausible that the influence of the environment varies during different periods of the day. We investigated the association between daily emergency ambulance calls (EC) for paroxysmal atrial fibrillation (AF) that occurred during the time intervals of 8:00-13:59, 14:00-21:59, and 22:00-7:59, and weather conditions and exposure to CO and PM10. We used Poisson regression to explore the association between the risk of EC for AF and environmental variables, adjusting for seasonal variation. Before noon, the risk was associated with an IQR (0.333 mg/m3) increase in CO at lag 2-6 days above the median (RR = 1.15, P = 0.002); a protective impact of CO on previous day was observed (RR = 0.91, P = 0.018). During 14:00-21:59, a negative effect of air temperature below 1.9 °C (lag 2-3 days) was detected (per 10 °C decrease: RR = 1.17, P = 0.044). At night, the elevated risk was associated with wind speed above the median (lag 2-4 days) (per 1-kt increase: RR = 1.07, P = 0.001) and with PM10 at lag 2-5 days below the median (per IQR (7.31 μg/m3) increase: RR = 1.21, P = 0.002). Individuals over 65 years of age were more sensitive to air pollution, especially at night (CO lag 2-3 days < median, per IQR (0.12 mg/m3) increase: RR = 1.14, P = 0.045; PM10 lag 2-5 days < median, per IQR increase: RR = 1.32, P = 0.001). The associations of air pollution and other environmental variables with acute events may be analyzed depending on the time of the event.
Keywords: Carbon monoxide; Emergency ambulance calls; Paroxysmal atrial fibrillation; Particulate matter; Risk; Weather.