Mild to moderate sleep respiratory events - One negative night may not be enough

Study objectives: Reports on the reproducibility of apnea-hypopnea indexes (AHIs) across sequential polysomnography (PSG) sessions are conflicting, le ading to a lack of clear recommendations on the optimal use of this techniq ue: is one night of monitoring sufficient or is a second night required in order to safely reject the diagnosis? Design: Retrospective comparison of two consecutive nights. Setting: Sleep unit of a tertiary-care facility. Patients: Two hundred forty-three subjects with suspected sleep apneas, Interventions: Two sequential PSG sessions in a sleep unit. Measurements and results: Using analysis of covariance for repeated measure s, with age and body mass index as covariates and gender as a cofactor, a c lassic first-night effect was found for sleep variables. In addition, a nig ht effect was demonstrated for sleep respiratory variables. Moreover, the h igh variability of AHIs showed that many patients had their condition diagn osed on only one of the two nights, and more often on the second night than on the first. The gain in detection by adding a second night when the resu lts of testing on the first were negative was between 15% and 25%, accordin g to the AHI obtained on night 1. Conclusions: Considering the disability associated with sleep apnea/hypopne a syndrome, as well as its global cost for society, the present study shows that it is worth performing two consecutive PSG sessions or at least a sec ond one when the result of the first one is negative in all patients admitt ed for apnea detection.