Study objectives: Reports on the reproducibility of
apnea-hypopnea indexes (AHIs) across sequential polysomnography (PSG)
sessions are conflicting, leading to a lack of clear recommendations on
the optimal use of this technique: is one night of monitoring
sufficient or is a second night required in order to safely reject the
Design: Retrospective comparison of two
Setting: Sleep unit of a
Patients: Two hundred
forty-three subjects with suspected sleep apneas.
Interventions: Two sequential PSG sessions in a sleep
Measurements and results: Using analysis of
covariance for repeated measures, with age and body mass index as
covariates and gender as a cofactor, a classic first-night effect was
found for sleep variables. In addition, a night effect was demonstrated
for sleep respiratory variables. Moreover, the high variability of AHIs
showed that many patients had their condition diagnosed 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 results of
testing on the first were negative was between 15% and 25%, according
to the AHI obtained on night 1.
Considering the disability associated with sleep apnea/hypopnea
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 second one when the result of the first one is negative in all
patients admitted for apnea detection.