Characteristics And Predictors Of Insomniacs Sleep-State Misperception

Objective: The aims of this study were to determine the prevalence of sleep-state misperception and to identify any differences in the characteristics of insomniacs with and without misperception, and to assess the probable predictors of this disorder in insomniacs.Methods: A clinical-based cross-sectional survey was performed. In total, 33 insomniacs with sleep-state misperception and 92 insomniacs without sleep-state misperception which all diagnosed by polysomnography(PSG) were chosen from the sleep Medicine Center of West China Hospital were included in this study. After the full-night PSG study, all the subjects completed the self-reported questionnaires with demographic factors, health and medical history, sleep-related scales and psychiatric measurements including the Insomnia Severity Index(ISI), Pittsburgh Sleep Quality Index(PSQI), the Epworth Sleepiness Scale(ESS), Beck Depression Inventory(BDI), Hospital Anxiety and Depression Scale, Short-Form 36-Item Health Survey and the Morning Questionnaire(MQ). The sleep onset latency estimation error was calculated by subtracting the objective SOL from the subjective SOL values, while the total sleep time estimation error was calculated by subtracting the objective TST from the subjective TST(PSG) values. Descriptive analysis, unpaired t test, t’ test,Chi-Square and stepwise regression were performed by SPSS 17.0.Results:1. The prevalence of sleep-state misperception in insomniacs was 26.4%. The patients with misperception were significantly younger than those without misperception [(42.70 ± 8.13) years vs.(51.41 ± 6.81) years], the difference was significant(P<0.001). There were no significant differences between the two groups with respect to other variables such as gender, body mass index and underlying diseases(P>0.05).2. The misperception group exhibited relatively normal sleep architecture, their TST were significantly longer than in those without misperception[(442.12±30.20)min vs.(395.06±44.12)min], and their latency to sleep onset[(17.00±13.31)min vs.(33.59 ± 28.97)min] and latency to rapid eyemovement sleep[(109.80±53.62)min vs.(141.89±69.04)min] were significantly shorter, those differences were significant(P<0.05). The misperception group had a shorter wake-after-sleep onset time [(35.62±16.70) min vs.(94.65±51.13)min] and better sleep efficiency[(89.89% ± 3.07%) vs.(76.07% ± 9.18%)], those differences were significant(P<0.001). Furthermore, the misperception group had a nearly normal sleep architecture, while those without misperception had a shorter REM sleep time relative to TST [(17.29%±7.87%)vs.(22.88%±5.13%)] and a longer light sleep time(N1+N2 stage) relative to TST [(62.48%±5.92%) vs.(57.00%±5.09%)], those differences were significant(P<0.05). There were no significant differences between the two groups with respect to MSLT scores[(13.16±4.39)min vs.(13.70±4.41)min, P>0.05].3. The tendency toward underestimation of subjective total sleep time and overestimation of subjective sleep onset latency was apparent in both groups, the total sleep time estimation error was significantly greater in those with misperception than in those without misperception [(-160.30±83.78) min vs.(-70.82±65.60) min, P<0.001], the sleep onset latency estimation error was also significantly greater in those with misperception than in those without misperception [(44.21±25.62) min vs.(7.66±4.09) min, P<0.001].4. In terms of sleep-related measures, including ISI, PSQI, ESS scores, there were no significant differences between those with and without misperception. Although ESS scores were within the normal limits, the ISI scores revealed moderate to severe insomnia in both groups(22.18±3.08 vs. 21.73±2.92), and the total PSQI score revealed poor sleep quality in both groups(15.27±1.28 vs. 14.95±1.37). The psychiatric variables did not differ significantly between the two groups, with both groups demonstrating a depressive mood, anxiety, and poor quality of life.5. Multiple regression analysis was used to determine the factors predicting subjective TST and subjective sleep quality. In both groups, the objective SE, as calculated from the PSG, was a significant factor predicted with subjective TST. In the misperception group the total PSQI score was also significantly predicted with subjective TST, the effect size being the same as that for objective SE. In terms of subjective sleep quality, the subjective TST was a significant factor related to PSQI score in the misperception group, while the BDI score and age were significant effect factors in those without misperception.Conclusions: 1. Underestimation of subjective TST and overestimation of sleep onset latency is a common tendency among insomniacs with sleep-state misperception.2.The subjective quality of sleep and psychiatric parameters were similar in the two groups, although the objective sleep architecture was relatively normal for the misperception group.3.Multiple regression analysis revealed that both sleep efficiency and sleep quality were significant factors predicted with subjective TST in the misperception group, while only sleep efficiency was significant in those without misperception. Subjective TST was a significant effect factor with respect to sleep quality in the misperception group, while the Beck Depression Inventory score and age were significant factors in those without misperception.