Screening of Patients with Snoring and Obstructive Sleep Apnoea using Heart Rate Variability Indices

Snoring and obstructive sleep apnea (OSA) are common disorders. Snoring associated with excessive daytimesleepiness is the most prevalent symptoms of OSA. Heart rate variability (HRV) is altered in patients with OSA and the degreeof alteration may be linked to the severity of OSA. Alterations in HRV in 24 hour tachograms have recently been used in screeningOSA patients. Autonomic components causing HRV can be reliably studied using spectral analysis techniques involving fast Fouriertransformation (FFT). Methods: Twenty-three subjects, ÆÌ3 with severe OSA and ÆÌ0 controls matched for age and body mass index,were selected from patients who had undergone polysomnography (PSG) for snoring at Sultan Qaboos University Hospital, Oman. A24- hour electrocardiogram (ECG) Holter recording was done at home, starting at ÆÌ0am. Spectral analysis of ECG from sleep Holterand PSG recordings was analysed using fast Fourier transformation (FFT). Results: The ECG RR intervals of snorers with OSA weresignificantly shorter than in snorers without OSA (p 0.0ÆÌ). The low frequency (LF) spectral densities of HRV from polysomnographyand Holter were significantly higher in OSA patients than in snorers, (p 0.000ÆÌ). The power spectral density of the high frequencybands was similar in the two groups. The overnight ECG Holter accurately identified all ÆÌ3 snorers with severe OSA. Conclusion: Thespectral power of the LF band obtained using FFT of sleep HRV from Holter tachograms may be a useful and cost effective test inidentifying snorers with severe OSA.