Excessive sleepiness and selected aspects of functioning and the quality of life of patients suffering from obstructive sleep apnoea

INTRODUCTION

Obstructive sleep apnoea (OSA), which is the most common form of sleep-disordered breathing (SDB), is a widespread health problem in the population of highly developed countries and can be diagnosed in 22% of men and 17% of women [1]. In Poland it is estimated that 16.7% of men and 5.4% of women suffer from OSA [2].
Factors that increase OSA risk include: male gender, age (over 40 years in the case of men and 50 years in the case of women), high blood pressure, obesity, neck size (neck circumference ≥ 43 cm in the case of men and ≥ 41 cm in the case of women), hypothyroidism, acromegaly as well as smoking and drinking alcohol (especially before bedtime), taking some medicines (including sedatives), and also some anatomical upper airway and facial skeleton anomalies [3, 4].
The condition is characterised by recurrent episodes of cessation of breathing (apnoea) and shallow breathing (hypopnoea) during sleep when the muscles of soft palate, uvula, tongue, and the back wall of the throat become too relaxed and, consequently, the airway becomes partially or completely blocked despite regular chest and abdominal breathing movements. As a result, the efficiency of pulmonary ventilation is decreased (incidents of hypoxia and hy-percapnia), the pressure inside chest tends to fluctuate, and the sympathetic nervous system is activated [4-6].
Obstructive sleep apnoea is diagnosed when at least five incidents of apnoea are observed and the breaks be-tween consecutive breaths exceed 10 seconds, reduction in upper airflow reaches at least 50% of the initial flow, and the reduction in arterial blood oxygen saturation exceeds 4% [4, 5].
Obstructive sleep apnoea symptoms can be divided into night symptoms that affect the quality of sleep and daytime symptoms. The most characteristic night-time symptoms include loud snoring, shortness of breath, choking sensation, frequent awakening during the night, periodic limb movements, and excessive sweating. The daytime symp-toms include, for example, excessive daytime sleepiness, morning fatigue and headaches, decline in cognitive processes and concentration, lower libido, irritability, and mood swings [5, 7, 8].
Moreover, obstructive sleep apnoea is responsible for sparking off the mechanisms that can have a serious ne-gative impact on health; for instance, cardiovascular problems (hypertension, cardiac arrhythmias), pulmonary pro-blems (pulmonary hypertension), or metabolic disorders (e.g. insulin resistance, diabetes) [2, 9].
Obstructive sleep apnoea also has a negative influence on daily biopsychosocial functioning. The incidence of sleep pattern disorders accounts for the fact that patients wake up feeling tired, easily doze off during the day or while performing daily routines, have problems with concentration, and suffer from lowered mood. As a result, they tend to isolate themselves and have difficulties maintaining positive interpersonal relations. However, it cannot be denied that an increased risk of home and work accidents as well as road accidents should be mentioned as the most serious con-sequence of an excessive daily sleepiness [3, 9]. Most of these phenomena become more intense with increasing sleepi-ness during the day [10].

AIM OF THE STUDY

The objective of the study was to assess the intensity of sleepiness during the day and its influence on selected aspects of daily functioning of patients suffering from obstructive sleep apnoea.

MATERIAL AND METHODS

The study was carried out in a group of patients hospitalised on a pulmonology ward in one of the hospitals in the Małopolska region. The examined group consisted of 49 patients (19 women and 30 men) diagnosed with obstructive sleep apnoea. They gave their informed written consent to participate in this project. The respondents were aged betwe-en 27 and 80 years (the average age was 55.27 ±12.80 years).
The study was conducted with the application of a diagnostic survey method making use of the following rese-arch tools: a self-designed questionnaire, the Epworth Sleepiness Scale (ESS), and a brief WHOQOL-BREF scale (World Health Organisation Quality of Life-BREF).
The self-designed questionnaire consisted of a sociodemographic part and 12 questions referring to selected aspects of respondents’ physical, social, and emotional functioning.
The Epworth Sleepiness Scale is a research tool that allows the assessment of the intensity of daytime sleepi-ness while being engaged in particular daily activities. In general, ESS scores can be interpreted as follows: 0-9 – normal daytime sleepiness, 10-14 – moderate excessive daytime sleepiness, 15-24 – severe excessive daytime sleepiness [11].
The WHOQOL-BREF scale is an instrument aimed at assessing general quality of life as well as all its domains (physical health, psychological, social relationships, and environment). The scale makes it possible to assess an indivi-dual’s overall perception of quality of life and an individual’s overall perception of their health [12-14].
The statistical analysis was conducted with the application of STATISTICA 10.0 PL. Calculations were carried out by means of the following tests: 2 test, Kruskal-Wallis test, U Mann-Whitney test, and Spearman’s rank correlation coefficient. In all analyses the significance level was set at  = 0.05.
The study was conducted following the ethical principles of the Declaration of Helsinki and the Convention on Human Rights and Biomedicine of the Council of Europe.

RESULTS

The study was conducted in a group of 49 people (19 women and 30 men) aged between 27 and 80 years. The gro-up of respondents aged between 51 and 60 years was the most numerous, whereas the least numerous was the group of respondents aged under 40 years. The average age of patients was 55.27 ±12.80 years. The lowest percentage of re-spondents had only elementary education (4.08%; n = 2), whereas secondary education was declared by 32.65% of patients (n = 16), and the same number of people declared higher education. The remaining group was made up of pa-tients with vocational education. Professionally active people made up 32.65% of the patients (n = 16). Most of the respondents considered their financial status to be average; good or very good financial status was declared by 28.57% of patients (n = 14), and 10.21% of them (n = 5) regarded their financial status as bad or very bad.
Epworth Sleepiness Scale is an instrument that allows for subjective assessment of the intensity of excessive daytime sleepiness in a group of OSA patients. The average ESS score obtained by the respondents was 10.11 ±5.60 (Table 1).
The patients with moderate excessive daytime sleepiness made up the most numerous group (42.86%; n = 21), whereas severe excessive daytime sleepiness was observed in 16.33% of patients (n = 8). The assessment of the intensi-ty of daytime sleepiness according to ESS scale is presented in Figure 1.
Respondents were asked about their problems/complaints that stem from abnormal respiration during sleep and impede their daily functioning (Table 2).
Daytime fatigue was the most frequent problem reported by the respondents (87.76%; n = 43), whereas the lo-west percentage of the respondents noticed a negative influence of fatigue/sleep deprivation on their sexual life (32.66%; n = 16).
Overall perception of quality of life assessed by OSA patients reached an average level of 4.96 ±0.78. The envi-ronmental domain received the highest scores, and the psychological one – the lowest (12.68 ±2.53), which means that in this domain the respondents assessed their quality of life as average. As far as respondents’ self-assessment of their health is concerned, the average score in the examined group was 3.11 ±0.97 (Figure 2).
An analysis of a correlation between particular sociodemographic factors and the intensity of excessive sleepi-ness assessed according to the ESS scale showed a negative correlation between respondents age and their ESS score (R = –0.283, p = 0.048). Younger patients felt more severe sleepiness as compared to older patients. The other sociode-mographic factors analysed in the study (gender, education, professional activity, and financial status) had no signifi-cant influence on the perception of daytime sleepiness in the examined group.
An analysis of the authors’ own studies showed a correlation between ESS scores and the complaints reported by the respondents, including sleepiness/fatigue after a full night of sleep, daytime fatigue, difficulties with performing household duties because of fatigue and/or sleep deprivation, and memory and/or concentration problems. The pa-tients who reported these problems scored significantly higher on the ESS scale than the patients who did not experien-ce these problems (p = 0.024, 0.004, 0.011, and 0.022, respectively).
The subject of another analysis was the influence of problems resulting from sleep disorders on respondents’ quality of life. The quality of life was significantly higher in the group of respondents who did not experience fati-gue/sleepiness after a full night of sleep than in the group of respondents who reported this problem (p = 0.044). A signi-ficantly lower quality of life was typical of the people who declared that their fatigue/sleepiness had a negative impact on their sexual life, in comparison to the respondents who did not notice a correlation between their OSA problems and their sexual life (p = 0.008). The other complaints reported by the respondents had no significant impact on the respon-dents quality of life (p > 0.05).
No correlation was found between the level of perceived excessive daytime sleepiness and respondents’ quality of life (R = –0.224, p = 0.122).

DISCUSSION

Obstructive sleep apnoea consists of recurrent cessation of breathing and episodes of shallow breathing during sleep [15]. OSA may have various aetiology and intensity; however, even its mild form is connected with the incidence of numerous consequences of hypoventilation such as excessive daytime sleepiness and other conditions, which are fol-lowed by deterioration of biopsychosocial functioning [5, 7, 8].
The most frequent complaints in the examined group of respondents included the following: daytime fatigue (87.76%), fatigue after a full night of sleep (71.43%), irritability, anxiety, likelihood of losing one’s temper and more frequent conflict situations (65.31%), memory and concentration problems (63.27%), and lowered mood (57.14%).
The incidence of excessive daytime sleepiness was a significant discomfort for OSA patients. Excessive dayti-me sleepiness accounts for frequent problems of dozing off during activities such as watching TV, reading, and even during a conversation [2]. In the studies conducted by Dębska et al. about half of the respondents reported excessive daytime sleepiness, and about one third of them reported severe excessive daytime sleepiness [16]. Similar findings were obtained by the authors of this study with mild excessive daytime sleepiness in 42.86% of cases and severe ex-cessive daytime sleepiness in 16.33% of respondents.
As was presented in the studies of other authors, the intensity of perceived excessive daytime sleepiness was affected by factors such as age, gender, and socioeconomic status [17]. This study, in turn, after analysing sociodemo-graphic features such as age, gender, education, professional activity, and economic status, discovered a statistically significant correlation only between respondents age and the intensity of perceived daytime sleepiness. The intensity of excessive daytime sleepiness tends to decrease with respondents’ age (R = –0.283, p = 0.048). The lack of correlation between the other features might have resulted from a low number of respondents. Therefore, it seems to be well based to conduct research in a more numerous group of patients.
Sleep is one of the basic physiological needs, and thus its deficiency, abnormal architecture, or disorders may give rise to a number of negative physical, psychological, and social consequences [18]. An analysis of scientific publi-cations shows that one of the most acute effects caused by obstructive sleep apnoea is difficulty in performing house-hold and professional duties. In turn, it significantly contributes to a decrease in patients’ self-assessment of quality of life [16, 17, 19]. Studies show that 65.31% of respondents find it difficult to perform their household duties because of their tiredness, whereas 55.10% have similar difficulties with their work-related duties. Moreover, the patients who re-ported difficulties with performing their household chores scored significantly higher on the ESS scale than the patients who did not report such problems (p = 0.011).
In the authors’ own study, overall quality of life was assessed as high. The domain of environment obtained the highest scores, whereas the domain of psychology – the lowest. The respondents who reported fatigue and sleepi-ness after a full night of sleep assessed the quality of life the lowest. The studies of other authors indicate that the fac-tors such as age, gender, education, duration of the disease, and place of residence affect quality of life [17, 20-22]. On the other hand, this study did not prove a correlation between WHOQOL-BREF scores and patients’ age, gender, and professional activity, which might be explained by lack of representativeness of the examined group.
Sleep structure disorders and night-time hypoxia, which are typical of OSA patients, lead to excessive daytime sleepiness and, consequently, to a decrease in the efficiency of cognitive processes, difficulties in daily functioning (both in psychological and social spheres) and, as a result, lower quality of life and even an increased risk of life-threatening injuries and accidents. These observations have been confirmed by the studies of numerous authors as well as by the results obtained by the authors of this study [23, 24].
In this context, it seems particularly important to take all possible measures in order to improve OSA patients’ quality of sleep of and, by the same token, their biopsychosocial condition. These measures include health education, which is a crucial complement of appropriate treatment. This education should be aimed at the specific needs and pro-blems of OSA patients. In order to achieve it, further wide-reaching research must be carried out in this group of pa-tients [8, 15].

CONCLUSIONS

In the examined group, the percentage of patients with moderate/mild excessive daytime sleepiness was the highest, while percentage of patients with pathological daytime sleepiness was lowest.
As far as sociodemographic characteristics are concerned, a statistically significant correlation was found only between respondents’ age and the intensity of daytime sleepiness. Younger patients felt drowsier compared to older respondents.
The patients who experienced sleepiness and fatigue after a full night of sleep, difficulties in fulfilling their hou-sehold chores due to tiredness and/or sleep deprivation, as well as memory and/or concentration problems obtained higher ESS scores in comparison with the respondents who did not report such problems.
No correlation was observed between the intensity of perceived daytime sleepiness and respondents’ quality of life.

Disclosure

The authors declare no conflict of interest.