Aquino Lemos, V., Antunes, H. K. M., Santos, R. V. T., Lira, F. S., Tufik, S., & Mello, M. T. conducted an experiment to research the effect that hypoxia has on the human body's sleep patterns, mood and cognitive functions. The research was published on may 22nd, 2012 with 10 admissable results from a total of 11 participants. 
Overall it was shown that exposure to hypoxia prevented participants from achieving efficient sleep cycles. Exposure to hypoxia also resulted in negative effects on participant's mood and cognitive ability. results also showed specifically strong reactions between hypoxia and a individual's depressive mood.
Sleep Architecture and Respiratory Patterns
|Statistics||Mean||1 SD||Mean||1 SD|
|Ave O² saturation||95.46||1.07||78.57||3.24|
|Total Time Sleeping||353.15||51.47||282.45||73.15|
|Total Respiratory Events||19.44||3.76||198.95||72.63|
Table one contains several variables that have been negatively affected by a prolonged (>14 hrs) exposure to hypoxia. It can be seen that the exposure to hypoxia prevents the participants from achieving a consistent rhythm to their sleep, as well as increases the amount of respiratory events by a large amount.
|Statistics||Mean||1 SD||Mean||1 SD|
Table 2 includes the scores of the participants mood states. Lower values in vigor indicated low vigor while for the remainder of variables higher values represented greater endorsement to the specific variable.
As seen from the above table, hypoxia's effect on a participants mood is generally negative with the exception of the confusion levels of the participants. Hypoxia does not seem to cause the participant to be more confused then in normoxia, however, it is noted that the P value given for the variable 'confusion' was 0.91 (p < 0.05) thus making the result not statistically significant. Additional research might have to be conducted to establish any possible relation between exposures to hypoxia and confusion levels.
|Exercise||Mean||1 SD||Mean||1 SD|
|Digit Span||Sum of the Orders||20.1||1.59||13.7||2.11|
|Corsi Blocks||Direct/Inverse Sum||17.9||1.91||9.70||1.76|
|Sequence of numbers and Letters||Total Correct||12.4||1.07||6.90||1.28|
|Stroop color test||Average of 3 timings||27.8||3.63||39.0||8.34|
|Average of 3 errors||0.63||1.01||1.9||0.92|
Table 3 contains a summary of the results obtained in the research to establish a link between an exposure to hypoxia and a participants cognitive function. Every test/game administered received lower results from pariticipants who were hypoxic. Of particular interest is in the stroop colour test where participants not only took longer to complete the test, but also commited more then twice the number of errors.
Sleep to Mood State and Cognitive Functions
|Measurement||Depressive Mood||Impt||Tension||Impt||Confusion||Impt||Mental Control||Impt||Working Memory||Impt||Mental Manipulation||Impt||Inhibitory Control||Impt|
|Number of Arousals||-||-||-||-||0.69||Med||-||-||-||-||-||-||-||-|
The above results shows correlation between the effects of hypoxia on sleep states and on a person's mood state and cognitive function. depression, tensions, Mental minipulation and Inhibitory Control have all shown to have a strong reaction to any changes in a participants sleep state (at least more then 0.70 correlation).
|Measurement||Depressive Mood||Importance||Inhibitory Control||Importance|
|Sleep Efficiency||- 0.74||High||-||-|
Table 5 further explain the effects of hypoxia on a participants mood state and cognitive function with depression once again showing a high correlation with sleep efficiency. It can be concluded from the above results that hypoxia, which causes abnormalities in a participants sleep state, will have a high correlation to the level of depression experienced by a person. While the article also includes the corresponding correlative values to normaxia, certain values were not included in the ariticle and might not have supported the authors claims.
The research article mostly includes results and statistical analysis of the value derived from the experiment. An inferential analysis was done for this web page to include possible conclusions that can be drawn from the data obtained and the degree in which hypoxia has on a variable.
11 participants were selected for the study, their primary characteristics were:
|Age (Years)||24.9 (5.02)|
|Education (Years)||15.6 (1.7)|
|Height (Metres)||1.72 (0.1)|
|Weight (Kilograms)||74.5 (13.8)|
|Body Mass Index (Kg/m²)||24.6 (3.3)|
|Daily Energy Expenditure (kcal)||1784.8 (227.0)|
During the actual experiment itself, one participant had to be removed after experiencing severe side effects (vomitting and headaches), as such only 10 results were admissable for the research. (N = 10)
A Post-test/Pre-test experimental research single blind design to ascertain the effects of exposure in high altitude on sleep patterns, mood and cognitive functions. Volunteers first undertook the tests and questionaires under normaxic conditions, were exposed to hypoxic conditions (simulated 4500m altitude) and then tested again for variances in results.
Over the course of 48 hours, participants were subjected to 24 hours in a controlled normaxic condition wihlst they under went severals tests and then 24 hours under hypoxic conditions where they underwent the same tests. The results were tabulated and compared for analysis. the conditions were controlled with the use of a normobaric chamber.
Variables and Measurements
Sleep Architecture and Respiratory Patterns
A calibrated Embla digital polygraph N7000 amplifier with Somnologica Studio software was used for the experiment.
Brunel mood scale
The scale was used to establish scores relating to how the subject feels and his mood. The variables identified are:
- Depressive mood
It consisted of 24 adjectives that described the mood of the paritcipant and they were required to select a value along a likert scale from 1 - 4 to how much they associated with the adjective.
Several different tests were used to measure the participants cognitive abilities. they are:
- Digit Span Numbers which evaluates the concentrated attention and mental control of volunteers. Participants would first listen to a series of numbers and then repeat them back first in its normal sequence and in the later phase, its inverse sequence.
- Sequence of Number and Letters which evaluates the volunteer's mental manipulation ability and working memory. A series of aplhabets and numbers would be given to the participant for them to rearrange in to ascending or alphabetical order.
- Corsi Blocks which evaluates the individuals focused attention span and mental control. irregularly shaped cubes were given in a sequence to participants to touch, they would then be required to repeat the sequence in order or in an inverse order.
- Random Number Generation evaluated the volunteers working memory and cognitive functions such as executive function and mental processing speed and required the participant to give 100 numbers generated randomlyby themselves at one number per second.
- Stroop Colour Word Test which tested a participants selective and concentrated attention capacity, cognitive flexibility, inhibitary control and mental processing speed. it consisted of several phases where participants were given cards with colours written on them in variating colours and participants were either suppose to read out the colour of name the colour use to write the word.
Only the Brunel Mood Scale was validated to the population from which the participants came from. It is unclear if any of the other tests were validated to the brazilian population.
While the article has shown to have a fair amount of validity in its measurements, there are several limitations to the results provided by the. Firstly, the results cannot be generalized to a wider population because the participation size was so small and because the selection criteria stringent. While the results can be generalized to individuals within the same categories, it still leaves many other people from the population who cannot use this information accurately. Secondly, the study does not help in predicting reactions for individuals who have had multiple or regular exposures to hypoxia. High altitude occupations such as pilots stand to benefit greatly with information on how their body will react to a consistent change in oxygen saturation; unfortunately, this study will not be able to assist them. Finally the study was also conducted in a set altitude of 4,500m above sea level and does not provide and evidence of extrapolation for effect from other altitude levels, this information is difficult to use practically because of the nature of aircraft movement and mountainous ranges.
Contributors to this page
Authors / Editors
WU XI YU LUKE (2013).