Background: The mechanisms associated with the cardiovascular consequences of 
obstructive sleep apnea include abrupt changes in autonomic tone, which can 
trigger cardiac arrhythmias. The authors hypothesized that nocturnal cardiac 
arrhythmia occurs more frequently in patients with obstructive sleep apnea. 
Objective: To analyze the relationship between obstructive sleep apnea and 
abnormal heart rhythm during sleep in a population sample. Methods: 
Cross-sectional study with 1,101 volunteers, who form a representative sample of 
the city of São Paulo. The overnight polysomnography was performed using an 
EMBLA® S7000 digital system during the regular sleep schedule of the individual. 
The electrocardiogram channel was extracted, duplicated, and then analyzed using 
a Holter (Cardio Smart®) system. Results: A total of 767 participants (461 men) 
with a mean age of 42.00 ± 0.53 years, were included in the analysis. At least 
one type of nocturnal cardiac rhythm disturbance (atrial/ventricular arrhythmia 
or beat) was observed in 62.7% of the sample. The occurrence of nocturnal 
cardiac arrhythmias was more frequent with increased disease severity. Rhythm 
disturbance was observed in 53.3% of the sample without breathing sleep 
disorders, whereas 92.3% of patients with severe obstructive sleep apnea showed 
cardiac arrhythmia. Isolated atrial and ventricular ectopy was more frequent in 
patients with moderate/severe obstructive sleep apnea when compared to controls 
(p < 0.001). After controlling for potential confounding factors, age, sex and 
apnea-hypopnea index were associated with nocturnal cardiac arrhythmia. 
Conclusion: Nocturnal cardiac arrhythmia occurs more frequently in patients with 
obstructive sleep apnea and the prevalence increases with disease severity. Age, 
sex, and the Apnea-hypopnea index were predictors of arrhythmia in this sample.