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Sleep apnea-hypopnea syndrome (SAHS) is a common sleep disorder prevalent in approximately 2% to 4% of adult people, and 20% to 40% of elderly people (1). Its frequency increases with age and body mass index (BMI), and it is about 2 to 4 times more prevalent in men than in women. Previous literature showed that patients with SAHS suffer from excessive daytime sleepiness (EDS) (2), cognitive impairment (3,4), and decreased psychological well-being (5,6). Some relational studies proposed a possible causal relation between the nocturnal polysomnographic (PSG) features of SAHS and daytime function (5). Previous reports have linked SAHS with depression, anxiety, and other psychological problems (6). Some investigators believe that the impairments can be reversed following appropriate treatment (7). Others, however, have found that some psychological impairment persists even after treatment (8), most probably owing to irreversible anoxic central nervous system damage. Conversely, the association between SAHS and psychological abnormalities could not be confirmed in other studies (9,10). Although patients with SAHS suffer from fragmented sleep and decreased arterial oxygen saturation, the relation between SAHS and mental changes or psychological abnormalities in some of these patients is still uncertain, as are the determinant factors of these impairments. In addition, the degree to which the psychological symptomatology of sleep apnea can be correlated with the demographic, clinical, and PSG features of the disorder is of both clinical and scientific interest. Given the uncertainty in the literature, we investigated psychological symptoms in 30 SAHS patients and 30 healthy control subjects. We then reevaluated the association between SAHS and psychological symptoms in 30 SAHS patients. This enabled us to examine the roles of nocturnal PSG variables and EDS in the possible linkage. Subjects and MethodsSubjects Questionnaires The second questionnaire was the Symptom Checklist-90 (SCL-90) (12), a well-established, self-report, clinical rating scale that assesses outpatient symptomatic psychological disturbance. It comprises the following 9 primary symptom scales: somatization, obsession–compulsion, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, and psychoticism. We used the General Severity Index (GSI) of SCL-90, calculated by dividing the total score by 90, to indicate current psychological status. The third scale used was Epworth Sleepiness Scale (ESS) (13), which comprises 8 questions that evaluate subjective daytime sleepiness. With ESS $ 8, a patient may be considered to experience excessive daytime subjective sleepiness.
Nocturnal PSG Measurements Sleep records were analyzed for sleep stages and occurrence of apneas according to standard criteria (14). An apnea was defined as a complete cessation of airflow for at least 10 seconds. Hypopnea was defined as a decrease in airflow of at least 50%, with a concomitant fall of at least 4% in arterial oxygen saturation, followed by an arousal response (as indicated by EEG alpha waves, increased submental EMG levels, or increased body movements). The Apnea and Hypopnea Index (AHI) was calculated by dividing the total number of apnea and hypopnea episodes by the hours of sleep. Statistical Analysis ResultsDemographics
Nocturnal PSG Variables and Subjective Daytime Sleepiness Psychological Symptoms
We ranked the positive SCL-90 items (that is, the score of each item above 1.0) and listed the most common 10 items according to the frequency of each item in both groups. Then, we employed the chi-square test to analyze the most common positive items in the SAHS patients and in control subjects. The comparison showed that 53.3% to 86.7% of patients with SAHS suffered from psychosomatic symptoms. The most common positive symptoms in SAHS patients were decreased energy, feeling blocked while working, unstable sleep, faint in some parts of the body, pain in waist or back, headache, repeated checking, recalling things repeatedly, and difficulty in conversation. Further, except for the item “recalling things repeatedly,” these items occurred significantly more frequently in SAHS patients than in control subjects (P < 0.05) (Table 4).
Correlation Between Psychological Symptoms and Nocturnal Variables or Daytime Sleepiness DiscussionOur study examined the psychological status of SAHS patients and the association between nocturnal variables or subjective daytime sleepiness and several psychological profiles. The main findings that emerged from this study follow: 1. Compared with healthy control subjects, SAHS patients suffered from problems of sleep maintenance and architecture. We found an increased percentage of stage 1 sleep and wakefulness after sleep onset and diminishing slow wave sleep in SAHS patients. Further, all the SAHS patients suffered from intermittent respiratory disturbances and decreased arterial oxygen saturations. 2. SAHS patients had a higher GSI of the SCL-90 than did control subjects, as well as higher scores on 5 symptom scales; specifically, somatization, obsession– compulsion, depression, anxiety, and hostility. The most prominent psychological symptom among SAHS patients was somatization. 3. In our sample, 53.3% to 86.7% of patients with SAHS suffered from psychosomatic symptoms. In SAHS patients, most of the 10 most common positive items of the SCL-90 were significantly higher than in control subjects (P < 0.05). 4. The severity of psychological symptoms in SAHS patients was negatively related to total sleep time, percentage of stage 1 NREM sleep, and latency of NREM sleep. It was positively correlated to percentage of wake time after sleep onset and percentage of stage 2 NREM sleep or ESS. The SCL-90 questionnaire used in our study reflects a broad range of concomitant clinical psychological symptoms. Using the SCL-90, our findings are comparable with the earlier Minnesota Multiphase Personality Inventory (MMPI) data reported by Kales (16). Most subjects demonstrated increased mental stress, depression, anxiety, hypochondria, and somatization. However, some researchers have reported that depression is the most prevalent symptom of SAHS. Guilleminault and others reported that 24% of their sample had elevated depression scales on the MMPI (17). Similarly, Beutler and others found that SAHS patients could be discriminated from healthy control subjects on the basis of elevated MMPI depression scale scores (18). The degree to which the depressive symptomatology of SAHS can be correlated with the demographic, clinical, and PSG features of the disorder is both clinically and scientifically interesting. Few studies have revealed a correlation between somatization and SAHS. However, our study showed somatization to be a more severe symptom than others, according to the SCL-90 scales (the mean score of the SCL-90 somatization scale was as high as 1.08). This may be explained by the fact that Chinese often prefer to report body disability rather than emotional upset, especially when it accompanies physical disorders: when they suffered some mild physical diseases as well as mood disorders, these patients preferred not to report associated emotional upset but concentrated instead on the physical symptoms. Moreover, when it is confused by sleep disorders, depression is known to be a very difficult state to examination or diagnose. A more profound study is needed to evaluate sleep, mood disorder, and somatization. Further, we evaluated the depressive syndrome in a larger sample with SAHS, using the Beck Depression Inventory (BDI). Possibly, the Structured Clinical Interview for DSM-III-R (SCID) would be the better scale to determine the frequency of formal diagnoses of various psychological symptoms in SAHS. Few studies have addressed the relation between SAHS and anxiety symptoms. In fact, only Borak and others showed a correlation between anxiety and AHI (r = 0.68) in 20 patients with severe SAHS (19). Using the MMPI, Platon and others reported a slight association between anxiety and SAHS in 23 patients, compared with 17 healthy control subjects (20). However, our study indicated that anxiety may rather be related to fragmented sleep than to AHI or daytime sleepiness. The controversial results may be explained by different sample sizes and the roles of sex, age, and severity of SAHS.
Psychological symptoms of SAHS patients are likely to be correlates of sleep fragmentation or excessive daytime sleepiness (r > 0.2). They did not correlate importantly with the AHI or with minimum oxygen saturation of SAHS (r < 0.2). These findings may be consistent with those of Millman and others (5,21). We therefore conclude that it is sleep fragmentation rather than apnea or hypoxia that may be the risk factor for psychological symptoms in SAHS. Bardwell and others, however, reported a positive correlation between psychological symptoms and nocturnal hypoxia in patients with SAHS (22), while Kingshott and others reported a lack of strong relations between conventional nocturnal measures and daytime psychological well-being or cognitive performance in SAHS patients (23). Several comments can be offered to explain the controversial results regarding the association between SAHS and such psychological symptoms as somatization, depression, and anxiety. For example, the results of studies examining this linkage depend on sample size, sex distribution within study population, and the main method used to evaluate psychological status. Further, some patients have learned to adapt to their disease and upgrade performance when required. Such factors are likely to vary among individuals. The intersubject variances that naturally exist will mask any possible relations between nocturnal PSG variables and daytime psychological status. Conversely, we could not ascertain direction of causality with the Pearson correlation analysis: is bad sleep caused by anxious or somatic symptoms or do psychological symptoms affect sleep? Perhaps other methods, such as logistic regression analysis in a larger sample, can provide a more definite answer. ConclusionsIn our study, the existence or the severity of SAHS was associated with somatization, depression, anxiety, obsession– compulsion, and hostility. 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Kingshott RN, Engleman HM, Deary IJ, Douglas NJ. Does arousal frequency predict daytime function? Eur Respir J 1998;12:1264–70. Author(s)Manuscript received May 2002, revised, and accepted October 2002. 1. Doctoral Student of Psychiatry, Mental Health Institute, the Second Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China. 2. Professor of Psychiatry and Director, Department of Behavioral Medicine Science, Mental Health Institute, the Second Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China. 3. Professor of Psychiatry, Mental Health Institute, the Second Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China. 4. Associate Professor of Psychiatry, Mental Health Institute, the Second Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China. 5. Associate Professor of Psychiatry, Mental Health Institute, the Second Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China. 6. Technician, Mental Health Institute, the Second Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China. Address for correspondence: Dr Weihua Yue, Mental Health Institute, The Second Xiangya Hospital, Central South University, 86, Middle Renmin Road, 410011, Changsha, Hunan, People’s Republic of China. e-Mail: dryue@163.com
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