Objective: To study the mechanism of microarousal, its clinical meaning and value in the diagnosis and treatment of sleep apnea-hypopnea syndrome (SAHS).
Methods: 270 snorers (218 men, 58 women) mean aged 48 years underwent standard polysomnography (PSG), from which AHI, sleep latency (SL), number of oxygen desaturation >/= 4% per hour (ODI(4)) and microarousal index (MAI) were calculated. The overnight PSG recordings were also repeated during nCPAP in 28 patients, who have filled in the Epworth Sleep Score (ESS) before and after the treatment to evaluate the improvement of daytime sleepiness.
Results: Of the 270 snorers, there were 247 SAHS patients. Their AHI, ODI(4), MAI and SL were (43 +/- 27)/h, (44 +/- 23)/h, (29 +/- 16)/h and (12 +/- 17) min, respectively. AHI and MAI, ODI(4) and MAI were both positively correlated (r = 0.38, both P < 0.001). MAI and SL were negatively correlated (r = -0.15, P = 0.02), while AHI and SL, ODI(4) and SL were not correlated (r = -0.09, -0.02, P > 0.1). Of the 28 patients after CPAP, ODI(4) decreased from (48 +/- 25)/h to (4 +/- 9)/h, MAI decreased from (27 +/- 18)/h to (15 +/- 9)/h. The ESS and SL indicated that subjective and objective sleepiness improved.
Conclusions: Microarousals with at least 3 seconds EEG changes can be scored by computerized EEG analysis. MAI can reflect the severity of daytime sleepiness. MAI is complementary to AHI in the diagnosis and treatment of SAHS. After nCPAP, the patients' MAIs decreased and daytime sleepiness improved.