Sleep quality changes in insomniacs and non-insomniacs after acute altitude exposure and its relationship with acute mountain sickness

Abstract

Objective: We aimed to observe the changes in subjective sleep quality among insomniacs and non-insomniacs after acute ascending to 3,700 m and its possible relationship with acute mountain sickness (AMS).

Methods: A total of 600 adult men were recruited. Subjects' subjective sleep quality was evaluated by the Athens Insomnia Scale. AMS was assessed using the Lake Louise scoring system. Arterial oxygen saturation was measured.

Results: Despite insomnia resolution in only a few subjects, the prevalence of insomnia among insomniacs remained stable at 90% after rapid ascent to 3,700 m. However, among non-insomniacs, the prevalence of insomnia sharply increased to 32.13% in the first day of altitude exposure and progressively reduced to 4.26% by the 60th day of altitude stay. Moreover, the prevalences of insomnia symptoms decreased more markedly from day 1 to day 60 at 3,700 m among non-insomniacs than among insomniacs. At 3,700 m, the prevalence of AMS among insomniacs was 79.01%, 60.49%, and 32.10% on the first, third, and seventh days, respectively, which was significantly higher than that among non-insomniacs. Multivariate regression revealed that elevated Athens Insomnia Scale scores are an independent risk factor for AMS (adjusted odds ratio 1.388, 95% confidence interval: 1.314-1.464, P<0.001), whereas high arterial oxygen saturation and long duration of altitude exposure are protective factors against AMS.

Conclusion: Our results suggest that the effect of high-altitude exposure on subjective sleep quality is more marked, but disappears more quickly, among non-insomniacs than among insomniacs, whereas AMS is especially common among insomniacs. Moreover, poor subjective sleep quality is a risk factor for AMS.

Keywords: Athens Insomnia Scale; arterial oxygen saturation; rapid ascent; sleep.

Figure 1

Changes in the Athens Insomnia Scale score (A) and prevalence of insomnia (B) among insomniacs and non-insomniacs after arrival at high altitude. Notes: Compared to the values obtained at 500 m in the same group: *P<0.05, **P<0.01, ***P<0.001.

Figure 2

Changes in the prevalence of insomnia symptoms (Athens Insomnia Scale items) among insomniacs and non-insomniacs after arrival at high altitude. Notes: (A) Difficulty in sleep induction; (B) arousal during the night; (C) awakening in the early morning; (D) shortened total sleep duration; (E) decreased total sleep quality; (F) decreased sense of well-being in the daytime; (G) decreased functioning in the daytime; (H) daytime sleepiness. Compared to the values obtained at 500 m in the same group: *P<0.05, **P<0.01, ***P<0.001.

Figure 3

Comparisons of Lake Louise score (A) and the prevalence of AMS (B) between the insomnia and non-insomnia groups at 3,700 m. Notes: P-values are indicated as: *P<0.05, **P<0.01, ***P<0.001. Abbreviation: AMS, acute mountain sickness.

Figure 4

Comparisons of the prevalence of acute mountain sickness symptoms. Notes: (A) Headache; (B) dizziness/lightheadedness; (C) insomnia; (D) fatigue/weakness; (E) gastrointestinal distress. Comparisons were performed with chi-squared tests: *P<0.05, **P<0.01, ***P<0.001.