Journal of Sleep Disorders: Treatment and CareISSN: 2325-9639

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Research Article, J Sleep Disor Treat Care Vol: 5 Issue: 3

Subjective Quality of Sleep at High Altitude and Factors Associated with Poor Sleep Quality at High Altitude

Zubair UB1*, Mumtaz H2 and Khan NA3
1Department of Psychiatry, Regimental Medical Officer, Pakistan
2Resident ENT specialist and Head and neck Surgeon, CPSP, RWP, Pakisan
3Senior clinical research fellow ABM UL health board Moriston SA6 6NL, UK
Corresponding author : Zubair UB
750 CTE, Department of Psychiatry, Regimental Medical Officer, 750 CTE Balochistan, Pakistan
Tel: 0321-5209950
E-mail: [email protected]
Received: April 11, 2016 Accepted: June 13, 2016 Published: June 20, 2016
Citation: Zubair UB, Mumtaz H, Khan NA (2016) Subjective Quality of Sleep at High Altitude and Factors Associated with Poor Sleep Quality at High Altitude. J Sleep Disor: Treat Care 5:3. doi:10.4172/2325-9639.1000178



Aim: To determine the subjective quality of sleep among temporarily employed individuals at high altitude and analyze the factors associated with poor sleep quality.

Study design: Descriptive cross sectional study

Subjects and Methods: The sample population comprised of men living at a height of 4500 meter or more above sea level at Karakorum ranges in periphery of district Skardu for more than one month and less than three months and having normal BMI and good sleep quality at sea level. Quality of sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI). Relationship of Age, altitude, smoking, use of naswar, Frequent awakenings during the night, temperature-related discomfort, multiple calls for toilet, environment related issues (too many people in one room, snoring of companion, untidy room), uncontrollable worry, and breathing difficulties was assessed with the sleep disturbances.

Results: A total of 103 men with good sleep quality at sea level when screened through the PSQI were included in the final analysis. Out of them, 39.8% persisted with good sleep quality, while 60.2% had poor sleep quality at HA. After applying the logistic regression we found that smoking, frequent awakenings, uncontrollable worry and breathing difficulties had significant association with poor sleep quality at HA. Conclusion: This study showed a high prevalence of poor sleep quality among individuals at high altitude. Special attention should be paid to smokers and those who suffer from breathing difficulties or remain worried or anxious most of the times.

Keywords: Quality of sleep; High altitude; PSQI; Risk factors; Subjective assessment


Quality of sleep; High altitude; PSQI; Risk factors; Subjective assessment


Sleep and circadian rhythm of human body are important in maintaining homeostasis. Changing environment affects all the biological functions of the body including sleep [1]. Ascent to High altitude (HA) expose the individual to decreased atmospheric pressure and less oxygen tension which causes many changes in normal physiology of the body. The saturation of oxy hemoglobin begins to fall at 7000 feet above the sea level [2]. Various mechanisms and adaptations in the body allow it to compensate for this lack of oxygen. Stay at HA and prolong exposure to low tension oxygen can give rise to multiple health issues including diabetes, heart problems, hypertension, sexual dysfunction, anxiety, sleep apneas, reduced sleep efficiency and time, slow-wave sleep, and rapid eye movement [1,3,4]. Periodic breathing due to hypocapnic hypoxia involving alternating episodes of deep and shallow breathing is considered as main cause of sleep disturbances and frequent awakenings at HA, thus compromising overall quality of sleep and making it unrefreshing for the individual [5-8].
A study done at Aconcagua mountain base camp concluded that Sleep-related breathing disturbances become more troublesome at HA [9] Similar study showed that at HA sleep architecture is altered and there is marked decreases in rapid eye movement (REM) sleep [10-13].
Another study done in Switzerland revealed that rapid ascent is associated with poor sleep quality but there is improvement with acclimatization and increase in oxygen saturation [14] A subjective sleep study done by Polish physicians at Himalayas showed similar results by using a validated tool that quality of sleep is compromised at HA [15].
Sleep can also be affected by mental health issues encountered at HA. Various studies have concluded increased prevalence of anxiety and depression at high altitude contributing to the adverse symptoms of that harsh and unusual environment [8,16-19].
Cognition and mood of the individual is markedly affected if sleep pattern remains disturbed for more than 24 hours [19] so good quality of sleep is necessary for sound physical and mental health and carrying out of the normal daily activities [20].
A large number of individuals are employed temporarily at HA. Armed forces of various countries are engaged in alpine warfare which is unique in its kind. Tourism and Mountaineering also engage a lot of people to stay and work there. Sleep being one of the most important biological functions affecting and determining the overall health need to be assessed in detail in harsh environment of HA. No study has so far been undertaken in our country on people engaged temporarily at HA, to identify the quality of sleep and the associated risk factors. This study aims to investigate this interesting and unique phenomenon.

Subjects and Methods

This descriptive cross sectional study was conducted between 1st January 2015 to 31st March 2015 at Karakorum ranges in periphery of district Skardu. All subjects were male and above the age of 25 with normal BMI (20-24). Each had been living at high altitude (4500 meter above sea level or more) for more than one month and less than three months and had completed PSQI at sea level before the ascent. The subjects included soldiers deployed at HA, tourists, mountaineers and porters. They were transported by air till Skardu. From Skardu, by road till the height of 4200 meters. Beyond that ascent was on foot. Arrangements of travel and logistics were made either by Army or by Pakistan Tourism Development Corporation. Stay beyond 4200 meters was restricted to three months per year. Proper concrete accommodation was made till 4200 meters. Beyond that igloos meant for high altitude were installed for the stay. Individuals were properly acclimatized during the ascent. All individuals who did not give consent or those with age less than 25 or those with PSQI score 5 or more at sea level were excluded from the study. Subjects living there for less than one month or more than three months or permanent residents of that area or those who were unable to understand/complete the required questionnaire were also excluded. Subjects with BMI>24 or with any psychiatric or physical illness (DM, IHD, HTN, RA or other diseases of chronic nature) were also excluded from the study. After the application of inclusion and exclusion criteria, 103 subjects were included in the analyses.


Different methods and questionnaires are used for assessment of quality of sleep. We used Pittsburgh Sleep Quality Index (PSQI) which is most commonly used. The PSQI is an effective instrument for subjective measure of quality and patterns of sleep. Validated Urdu version of PSQI was applied [21] A global sum of “5”or greater indicates poor sleep quality.


After ethical approval from concerned ethical review committee and written consent from all the potential participants the subjects were provided with a detailed description of the study. Subjects with confounding variables like presence of chronic physical or mental illness or substance use were identified by detailed history taking and excluded from the study. The PSQI questionnaires were administered to the subjects and were asked to answer the questions according to their condition in last one month. Socio demographic variables were also collected. Variables in the study included age, altitude, smoking, use of naswar, frequent awakenings during the night, temperaturerelated discomfort, multiple calls for toilet, environment related issues (too many people in one room, snoring of companion, untidy room), uncontrollable worry, and breathing difficulties. Subjects aged more than 25 years with normal BMI (20-24) were included and environmental issues were described as too many people in one room, snoring of companion and untidy room. 4500 to 6000 meters and more than 6000 meters were the altitudes in which these subjects were employed. Frequent awakenings were classed as more than 03 awakenings per night. A history of tobacco smoking and naswar usage was obtained. People answering “yes” to question “do you smoke or have you smoked tobacco products regularly, in other words daily or nearly daily?” were classified as smokers or naswar users depending upon the product used. Stress from worrying continuously about the terrain, living conditions, weather and domestic problems despite efforts to relax was asked about in detail. Having more than two calls for toilet at night was regarded as sleep disturbance due to multiple calls for toilet.

Statistical Analysis

Characteristics of participants and the distribution of the PSQI score were described by using the descriptive statistics. Participants were resulted by categorical compared by good vs poor sleep quality. Chi-square was used to determine between-group variances in categorical correlates. Binary logistic regression analysis was done to evaluate factors related to quality of sleep. All statistical analysis was performed using Statistics Package for Social Sciences version 20.0. Chi-square test was used and differences between groups were considered significant if p-values were less than 0.05.


A total of 154 men were approached to participate in the study. 5 refused participation, 35 had poor sleep quality at sea level and 8 were ineligible due to exclusion criteria (1 gave history of psychoactive substance use, 2 had BMI more than 24, 1 had RA, 1 had HTN and 3 had DM). After being consented, an additional 3 did not provide complete data at baseline, leaving 103 participants who had completion of the PSQI. Out of them, 39.8% persisted with good sleep quality while 60.2% had poor sleep quality at HA. The mean PSQI global score in the study population completing the survey was M=7.98 (SD 3.86). As shown in Table 1 smoking, frequent awakenings, multiple calls for toilet, uncontrollable worry and breathing difficulties had significant association with poor sleep quality when chi-square is applied. Table 2 shows that that smoking, frequent awakenings, uncontrollable worry and breathing difficulties are strongly associated with poor sleep quality when regression analysis was done. Table 3 shows that there was statistically significant difference between frequent awakenings and sleep quality, habitual sleep efficiency, day time dysfunctions and global PSQI score. Table 4 shows that significant correlation as found between uncontrollable worry and sleep latency, sleep disturbance, habitual sleep efficiency and global PSQI score.
Table 1: Factors associated with sleep disturbance.
Table 2: The correlated factors relating to quality of sleep: the binary logistic regression.
Table 3: Distribution of sleep quality by question “Are there more than three awakenings per night of frequent awakenings?” depending upon the global score of all items of PSQI.
Table 4: Distribution of sleep quality by uncontrollable worry depending upon the global score of all items of PSQI.


To our knowledge this is the first ever study of its kind in our setup on individuals residing at HA exposed to a unique environment, which is challenging, new and stressful. The study is an attempt to record quality of sleep in an unusual environment where individuals are living to earn their livelihood or for protection of their mother land, in an attempt to identify risk factors common amongst those who have poor quality of sleep. In a developing country like ours getting employment regardless of nature and place of job is a matter of satisfaction, still hazards of high altitude brings about a lot of physical and psychological problems for the individuals working there [1,16,18,19]. Using PSQI we found that 60.2%of our subjects showed poor sleep quality which is in accordance with the available literature [12,14,15]. Some of the factors that may affect sleep quality at HA have been reported as chronic hypoxia, [22] breathing difficulties [23] or psychological issues [16]. Psychiatric morbidity at high altitude is supported by local as well as foreign data [18,24]. Sleep disturbances and psychiatric problems have a strong correlation [19,25]. A positive feedback cycle sometimes develop between the two which becomes very annoying for the patient and a challenge for health care physicians [25,26]. Though scope of our study is not to look for any psychiatric morbidity at HA as it is an established fact by now [16,27] but sleep being such a complex neurological function with physiological, psychological and social dimensions needs discussion from this point of view as well. It is easier for the health professionals to look for and address medical causes of sleep disturbances at HA but difficult for them to screen for mental health issues and even patient himself is usually unable to comprehend the psychosomatic issues which may give rise to multiple problems including bad sleep quality.
Various studies in past concluded that elder age and smoking are consistent correlates with poor sleep at HA [28-30]. The results in our study were similar for smoking, i.e., it has a clear link with poor sleep quality. No correlation with age was found as age bracket was not very wide in our study population because people with extreme of ages usually do not seek employment or visit such harsh terrains. The strong association of poor sleep quality with Frequent awakenings and breathing difficulties is also in line with studies done elsewhere [14,22]. Periodic breathing due to hypocapnic hypoxia is stated as main cause of frequent awakenings and in adequate sleep at HA.
There was significant correlation between uncontrollable worry and disturbed sleep in our analysis in. The worry about one’s future prospects in the harsh environment of high altitude is an expected finding. These worrying thoughts could be on account of the unique stresses of being away from family and lack of communication facilities [12,18,19]. This continuous worry can leads to depressive symptomatology [31] which can further lead to sleep disturbance [19].
No association of high PSQI score was established with different altitudes above 4500 meters, temperature related discomfort and environmental related factors. These results were different from studies done in past in foreign countries. [9,14] Reason might be proper acclimatization in our setup or availability of good administrative facilities in recent era. A larger study would be required to have a deeper understanding of these aspects.
There are many limitations in our study. The sample size, and use of self-administered questionnaires pose methodological issues. The findings cannot be generalized as our study population was not selected from a randomized sample of all the people employed at various peaks of this region including Himalayas and Hindukush. Similarly, the findings are not generalisable to individuals working at HA in other parts of the world. Another limitation is the chance that the subject may under or over report symptoms on selfadministered questionnaires like PSQI. We suggest further studies on a broader based and a more representative sample size using locally developed and standardized psychometric tools on the subject.


This study showed a high prevalence of poor sleep quality among individuals at high altitude. Special attention should be paid to smokers and those who suffer from breathing difficulties or remain worried most of the times. The findings of our study also call for a greater degree of understanding of their physical and psychological state during stay at HA.
UBZ planned the study, found references and wrote the final manuscript. HM collected the data and helped in writing the final manuscript. NAK helped in statistical analysis and writing the final manuscript.


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