We investigated the frequency of cardiac arrhythmias in patients suspected of 
having sleep apnea, and related them to the severity of apnea, snoring, and 
nocturnal hypoxemia. We prospectively studied 458 patients who had nocturnal 
polysomnography which included objective measurement of snoring (quantified by 
the number of snores per hour of sleep [snoring index (SI)] and maximum 
nocturnal sound intensity [(dBmax)], as well as examination of the 
electrocardiogram (modified lead 2). We found 58 percent prevalence of 
arrhythmias in patients with sleep apnea (apnea/hypopnea index = AHI > 10), vs 
42 percent in nonapneic controls (chi 2 = 16.7, p < 0.0001). Patients with 
arrhythmias had more severe apnea and nocturnal hypoxemia, but not snoring, than 
patients without arrhythmias. To examine separately the relationship between the 
prevalence of arrhythmias and snoring, nocturnal oxygenation, and apnea--we 
selected subgroups of patients "at the opposite ends of the spectrum" with 
respect to the severity of snoring, hypoxemia, and apnea. We found that 38 
percent of light snorers had arrhythmias vs 39 percent of heavy snorers, 82 
percent of patients with mean nocturnal oxygen saturation < 90 percent had 
arrhythmias vs 40 percent of patients with mean nocturnal oxygen saturation > 90 
percent (chi 2 = 7.4, p = 0.006), and 70 percent of patients with AHI > or = 40 
had arrhythmias vs 42 percent with AHI < or = (chi 2 = 9.2, p = 0.002). We 
conclude that patients with sleep apnea as a group have higher prevalence of 
cardiac arrhythmias than nonapneic patients and that snoring alone, without 
concomitant sleep apnea, is not associated with increased frequency of cardiac 
arrhythmias.