A meta-analysis of the first-night effect in healthy individuals for the full age spectrum

Objectives: The first-night effect (FNE) affects the accuracy of polysomnography (PSG) findings. However, the levels of FNE in different ages are unclear. Methods: We searched PubMed, Cochrane Library, Embase and Web of Science. The studies that reported sleep parameters by PSG for at least 2 consecutive nights from healthy individuals were included. The weighted mean differences were used to assess the effect size of differences in each sleep parameters between the first and second nights, as well as between the second and the third. Results: A total of 53 studies from 1422 subjects with mean age of 9.2-85.5 years were included. Meta-analyses showed that prolonged sleep onset latency, wake time after sleep onset and rapid eye movement sleep (REM) latency, accompanied by decreased total sleep time, sleep efficiency, and REM and increased non-rapid eye movement sleep stage 1 (N1) during the first night compared to the second (all P-value <= 0.001). No significant differences were observed in N2 and slow wave sleep, apnea-hypopnea index or periodic limb movement index (all P-value > 0.5). A non-linear association between FNE and age was observed: young adults (age 20-29 years) had the lowest level of FNE compared to other age ranges. Moreover, no significant differences were observed in most sleep parameters between the second and third night except more N2 and less REM in the second night (both P-value < 0.05). Conclusions: The FNE exists in most cases but only in the first night of PSG recording and is less pronounced among young adults. (C) 2021 Elsevier B.V. All rights reserved.