Journal of Mental Health
ISSN: 0963-8237 (Print) 1360-0567 (Online) Journal homepage: http://www.tandfonline.com/loi/ijmh20
Sleep problems among clinically depressed adults in China Sai Zuo, Marita P. McCabe, David Mellor & Yifeng Xu To cite this article: Sai Zuo, Marita P. McCabe, David Mellor & Yifeng Xu (2015) Sleep problems among clinically depressed adults in China, Journal of Mental Health, 24:1, 43-47 To link to this article: http://dx.doi.org/10.3109/09638237.2014.976856
Published online: 30 Dec 2014.
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Date: 13 September 2015, At: 04:15
http://informahealthcare.com/jmh ISSN: 0963-8237 (print), 1360-0567 (electronic) J Ment Health, 2015; 24(1): 43–47 ! 2015 Shadowfax Publishing and Informa UK Limited. DOI: 10.3109/09638237.2014.976856
ORIGINAL ARTICLE
Sleep problems among clinically depressed adults in China Sai Zuo1, Marita P. McCabe2, David Mellor2, and Yifeng Xu1 Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China and 2School of Psychology, Deakin University, Melbourne, Victoria, Australia
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1
Abstract
Keywords
Background: The aim of the study was to explore which variables predict poor sleep among clinically depressed Chinese adults. Methods: In total, 100 participants were recruited from Shanghai Mental Health Centre. The dependent variables were number of hours spent sleeping as well as the quality of sleep and number of times the participants woke during the night. The independent variables were gender, age, length of depression and severity of depression. The use of antipsychotic medication was controlled for in all analyses. Results: The results demonstrated that depression severity was the most important predictor of sleep quality and night waking. Gender and age were also found to be predictors of sleep problems. Conclusions: The findings demonstrated that depressed Chinese patients experienced similar relationships between sleep disturbance and depression to Westerners. Future studies should include other measures of sleep quality as well as variables consistently found to be associated with both depression and sleep difficulty, such as the use of addictive substances and psychosocial factors.
Depression, Chinese, sleep disturbance
Introduction Many depressed individuals report that sleeping problems are the single most debilitating feature of their disorder (Benca et al., 1997). Clinical studies have consistently found that problems with sleep are positively correlated with depressive symptomology, with depressed individuals reporting symptoms, such as difficulty falling asleep at night time, feelings of fatigue during the day, and awakening on multiple occasions throughout the night and in the early morning (Breslau et al., 1996). These symptoms have been profiled using electroencephalographic measurements during numerous clinical studies, which have indicated that the sleep onset latency, number of awakenings, wake after sleep onset and rapid eye movement sleep are increased in sufferers of depression, where total sleep time, sleep efficiency index, slow wave sleep and REMS latency (RL) are reduced (Dew et al., 1996; Thase et al., 1995). Despite the well-established link between sleep disturbance and depressive disorder, their temporal relationship is not easily determined. In unipolar depression, feelings of sadness, guilt, agitation and/or suicide can disrupt sleep onset, interrupt sleep continuity and precipitate early morning or recurrent awakenings. In turn, lack of sleep can maintain Correspondence: Prof. Marita P. McCabe, School of Psychology, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia. Tel: +61 3 9244 6856. Fax: +61 3 9244 6858. E-mail: marita.mccabe@ deakin.edu.au
History Received 24 October 2012 Revised 5 September 2014 Accepted 2 October 2014 Published online 30 December 2014
depressed mood state and impact the individual’s emotional regulatory abilities, thus further interrupting sleep (Sbarra & Allen, 2009). Research has found that sleep problems can also be a factor that precedes the clinical syndrome (Perlis et al., 1997). For example, even after controlling for a history of depressive symptoms, Breslau et al. (1996) found that prior insomnia was a significant predictor of depressive episodes. Additionally, Perlis et al. (2006) reported that insomnia increased the risk of development of depressive illness. These authors found across nine epidemiological studies, that individuals suffering from persistent sleep problems have a 3.5 times greater likelihood of experiencing a subsequent depressive episode than individuals without such difficulties. This association between sleep disturbance and depression is impacted by a number of other variables. Some of the variance in sleep difficulties found between clinically depressed individuals and controls has been significantly influenced by the participants’ age, with older people being more likely to experience sleep problems regardless of level of depression (Ford & Kamerow, 1989). Dew et al. (1996) stressed that sleep abnormalities are also influenced by the severity of the depressive episode. Their studies indicated that previous depressive episodes, duration of the present episode, type of the current depressive illness, gender and psychosocial stressors are all factors that can significantly impact on the relationship between depression and sleep quality. Most of the above-mentioned studies have focussed on the association between depression and sleep, with
Downloaded by [Stockholm University Library] at 04:15 13 September 2015
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S. Zuo et al.
Western populations. However, in a sample of 5001 Chinese adults from Hong Kong, Wong & Fielding (2011) found the prevalence rate of insomnia to be 39.4%, with women reporting significantly poorer sleep quality compared to men. Depression was also found to be significantly associated with sleep disturbances. However, little more is known about the relationship between sleep and depression in this nonWestern population. The Wong & Fielding (2011) study examined the association between depression and insomnia alone, and not other aspects of sleep quality. Given this strong association between depression and sleep disturbance among males and females from Western societies, it is argued that further research is needed to explore the factors that impact on this relationship, in a non-Western context. The aim of the present study was to explore which variables significantly predict poor sleep in a sample of Chinese adults. By studying these relationships in a Chinese population, it is possible to determine the generalizability of findings from Western populations. Depression levels, length of time the person has experienced depression and number of depressive episodes were postulated as predictors of various kinds of sleep disturbance. Furthermore, the present study was designed to determine the influence of age and gender differences on sleep quality in depressed Chinese adults.
Methods Participants The sample consisted of 100 participants from an outpatient clinic at Shanghai Mental Health Center, Shanghai, China, ranging in age from 19 to 62 years (comprised of 50 males: M age ¼ 41.94 years, SD ¼ 12.02 and 50 females: M age ¼ 40.64 years, SD ¼ 11.81). Recruitment continued until 50 males and 50 females agreed to participate in the study in order to satisfy power requirements (0.80) for the analyses. The inclusion criteria for participation in the present study was that participants were in the age range of 18–65 and have received a current diagnosis of major depressive disorder using The Chinese Classification of Mental Disorders (CCMD-3) (Chen, 2002). This diagnostic and classification tool has undergone substantial development and validation in China, with 114 psychiatrists from 41 mental health centers and psychiatric hospitals being involved in ensuring its validity and equivalence to the DSM IV (Chen, 2002). Thirty-two out of the 100 participants were receiving oral antipsychotic medication (Clozapine) in treating their depression at the time the study was conducted. All participants were currently receiving SSRI antidepressant medication. Measures Beck Depression Inventory (BDI-1) (Beck et al., 1961). Consisting of 21 items, the BDI-1 is a self-report measure that covers a range of affective, behavioral, cognitive and somatic symptoms thought to be indicative of unipolar depression. Each individual item has a set of four possible answer choices, ranging in intensity and rated on a scale of 0 to 3. Total possible scores range from 0 to 63, with higher scores reflective of increased levels of severity of depressive symptomology. The BDI possesses sound psychometric
J Ment Health, 2015; 24(1): 43–47
properties with high internal consistency reliability (a ¼ 0.89) and associated high levels of concurrent and construct validity (Rudd & Rajab, 1995). In a Chinese population, the BDI has been shown to be reliable and valid, and the internal consistency reliability was found to be 0.85 (Zeng & Zeng, 1987). Participants were asked to indicate the length of time they had suffered from depression in years (i.e. time since first episode of depression), the number of depressive episodes they had experienced, and the number of years they had received treatment. As there were no validated sleep scales in the Chinese language that evaluated the areas that we were targeting, the participants were asked to respond to singleitem questions regarding the following dimensions of sleep quality: the average number of hours of sleep they had per day, the number of times they woke up during sleep and the quality of their sleep in the past seven days (scored or a sevenpoint Likert scale from extremely poor to extremely good). Procedure Ethical approval was received from the Shanghai Mental Health Center. Participants were recruited from the Centre, which is affiliated with the School of Medicine at Shanghai Jiaotong University for 11 months from October 2009 to September 2010. Participants were informed about the study by staff at the Center, staff provided all people diagnosed with depression with a Plain Language Statement and Consent form. Treatment for patients’ depression was not affected by whether or not they participated in the study. The questionnaire (comprising the BDI and questions on sleep) was completed individually by participants and took about 10 min to complete. Analyses All data in the present study were analyzed using SPSS, version 17 (Chicago, IL). Data were screened for missing data, outliers and multicollinearity. Means, standard deviations and ranges for all depression and sleep pattern variables are displayed in Tables 1 and 2, respectively.
Results A series of t-tests were performed on the data to determine if there were any significant differences between males and females across each of the study variables. Results found that there were no significant differences across the variables except for the average number of times they woke up during Table 1. Mean, standard deviation and range of depression variables. Variable
Male M (SD)
Length of depression 5.96 (years) Number of depressive 2.20 episodes Years of treatment 3.24 Depression severity 28.72
Female M (SD)
Total M (SD)
Range
(8.21)
5.08 (5.12)
5.52 (6.94)
0–40
(1.58)
2.52 (1.39)
2.36 (1.49)
1–8
(5.32) 3.31 (5.23) 3.28 (5.25) 0–30 (9.55) 28.72 (7.70) 28.72 (8.63) 14–52
N ¼ 100. Depression severity ¼ Total Beck Depression Inventory (BDI) score.
Sleep problems in China
DOI: 10.3109/09638237.2014.976856
the night, t(99) ¼ 2.03, p50.05 and quality of sleep t(99) ¼ 2.34, p50.05, with females being more likely to wake up during the night and report a lower level of sleep quality compared to males.
Downloaded by [Stockholm University Library] at 04:15 13 September 2015
Regression analyses A series of hierarchical regressions were performed to determine which factors were most indicative of sleep quality whilst controlling for the use of antipsychotic medication. In each regression performed, the use of antipsychotic medication by participants did not contribute a significant amount of variance in the target variable. Therefore, whether or not participants were taking antipsychotic medication at the time of testing did not significantly influence the other predictor variables employed in each of the models. In the first regression (Table 3), gender, age, length of time suffering depression, depression severity (as measured by the BDI) and use of antipsychotic medication were employed as predictors of the average number of hours slept in the past 7 days. Results from the regression revealed that these five Table 2. Mean, standard deviation and range of sleep pattern variables.
Variable
Male M (SD)
Female M (SD)
Total M (SD)
Average no. hours slept 6.42 (2.41) 6.84 (2.66) 6.63 (2.53) in past 7 days Times awakened during 2.38 (1.70) 3.10 (1.84) 2.74 (1.80) sleep Sleep quality 3.36 (2.18) 2.44 (1.73) 2.90 (2.01)
Range 2–16 0–10 1–7
N ¼ 100.
45
variables together accounted for 14.7% of the variance explained in average number of hours slept after controlling for the use of antipsychotic medication, F(5, 99) ¼ 3.24, p50.05. Age was the only variable that significantly contributed to this regression, explaining 5.29% of the variance, ¼ 0.05, t ¼ 2.18, p50.05. In this sample, males who were older and reported a greater length of time experiencing depression and depressive symptoms were more likely to report fewer hours slept in the past 7 days. The second regression used the same variables of gender, age, length of depression and depression severity to predict quality of sleep, while controlling for the use of antipsychotic medication (Table 4). After controlling for the use of antipsychotic medication in participants, the total variance explained by this regression model was 45.50%, F(5, 99) ¼ 15.68, p50.001. Gender contributed significantly to the model, ¼ 0.25, t ¼ 3.21, p50.01, accounting for 6.15% of the variance explained in average quality of sleep. Females reporting poorer quality sleep compared to males. Depression severity was the strongest predictor in the regression, explaining 37.30% of the variation in quality of sleep, over and above that explained by the other variables in the model, ¼ 0.61, t ¼ 7.63, p50.001. The results demonstrated that the greater the severity of depression, the poorer the quality of sleep. The final regression employed gender, age, length of depression and depression severity to predict the average number of times the participants woke throughout the night, while controlling for the use of antipsychotic medication (Table 5). After controlling for antipsychotic medication use in participants, the total amount of variance accounted for by the model was 13.90%, F(4, 99) ¼ 3.03, p50.01. Gender was
Table 3. Summary of hierarchical regression analysis predicting the average number of hours slept in the past 7 days controlling for medication. Independent variables Step 1 Use of antipsychotic medication predicting hours slept Step 2 Use of antipsychotic medication Gender Age Length of depression (in years) Depression severity (as measured by the BDI)
B
SE
0.05
0.55
0.01
0.57 0.24 0.05 0.06 0.04
0.57 0.49 0.02 0.04 0.03
0.11 0.05 0.23 0.15 0.14
t 0.10
R2 ¼ 0.00
1.00 0.49 2.18* 1.33 1.43
DR2 ¼ 0.15**
N ¼ 100. *p50.05; **p50.01.
Table 4. Summary of hierarchical regression analysis predicting the sleep quality of depressed Chinese individuals, controlling for medication. Independent variables Step 1 Use of antipsychotic medication predicting sleep quality Step 2 Use of antipsychotic medication Gender Age Length of depression (in years) Depression severity (as measured by the BDI) N ¼ 100. **p50.01; ***p50.001.
B
SE
0.33
0.43
0.08
0.77
0.39 1.00 0.01 0.02 0.14
0.36 0.31 0.01 0.03 0.02
0.09 0.25 0.04 0.08 0.61
1.09 3.21** 0.42 0.85 7.63***
t R2 ¼ 0.07 DR2 ¼ 0.45***
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S. Zuo et al.
J Ment Health, 2015; 24(1): 43–47
Table 5. Summary of hierarchical regression analysis predicting the average number of times participants woke up during the night in depressed Chinese individuals, controlling for medication. B
SE
0.40
0.39
0.10
0.06 0.71 0.01 0.01 0.06
0.41 0.35 0.02 0.03 0.02
0.02 0.20 0.03 0.03 0.31
Independent variables Step 1 Use of antipsychotic medication predicting average number of times awoken during the night Step 2 Use of antipsychotic medication Gender Age Length of depression (in years) Depression severity (as measured by the BDI)
t 1.03
R2 ¼ 0.01
0.15 2.05* 0.30 0.30 3.03**
DR2 ¼ 0.13**
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N ¼ 100. *p50.05, **p50.01.
a significant predictor in the model, explaining 3.96% of variation in the number of times participants woke during the night, with females reporting waking up significantly more often than males, ¼ 0.20, t ¼ 2.05, p50.05. Depression severity was the most significant predictor, explaining 9.30% of the variance in average number of times participants woke up during the night, ¼ 0.31, t ¼ 3.03, p50.01. The results demonstrated that those participants with more severe depression were more likely to wake more frequently.
Discussion The present study aimed to examine the factors that have previously been identified as predictive of sleep disturbances in depressed adults within the context of a Chinese population. It was argued that such data would be valuable in order to ascertain whether the findings reported from western studies could be generalized to populations from other cultural groups. Previous findings within Western populations have found gender and age to be the most relevant demographic variables related to the prevalence of sleep difficulties among depressed people (Breslau et al., 1996; Ford & Kamerow, 1989). Generally, our data were consistent with these findings, with either gender or age being a significant predictor of each of the sleep problems investigated. Specifically, age was the only significant predictor of average number of hours slept among Chinese adults. Furthermore, gender significantly predicted sleep quality and number of times participants woke during the night, with females demonstrated a greater likelihood of suffering from these sleep disturbances. This is comparable to findings from Western populations, which have also found depressed females suffer from sleep disturbance more frequently, and at greater levels compared to males (Breslau et al., 1996; Ford & Cooper-Patrick, 2001; Ford & Kamerow, 1989). Our data are also consistent with the few studies investigating sleep problems in Chinese individuals, which have identified women as experiencing these difficulties more than men (Wong & Fielding, 2011). These findings further demonstrate that demographic variables are important to consider in the relationship between sleep disturbance and depression in a non-Western population. Other than the aforementioned demographic variables, depression severity, as measured by the BDI, was the single
most significant predictor of sleep difficulties in Chinese adults, explaining most of the variation in the regression models predicting sleep quality and number of times participants woke up during the night. These results are not surprising given the strong positive correlation that has consistently been found between these variables in other studies. As length of time suffering depression and use of antipsychotic medication were not significant predictors of any sleep difficulties investigated, the findings suggest that severity of depression is the most important factor to attend to when attempting to alleviate sleeping problems in depressed Chinese adults. Despite these significant findings, other variables that were not investigated in the present study may also impact on the sleep quality experienced by this non-Western population. The predictors of other measures of sleep disturbance, for example, sleep onset latency, napping and/or daytime sleepiness should also be examined. Further scales that have been validated with Chinese populations need to be used in this research. Examples of such scales are the Epworth sleepiness Scale, that measures the level of sleepiness (Chen et al., 2002) and the Pittsburgh Sleep Quality Index that measures insomnia (Tsai et al., 2005). Previous studies within nonWestern contexts have found that unemployment, anxiety, alcohol use, long-term health problems and poor mental health are also positive predictors of sleeping difficulties in Chinese adults (Wong & Fielding, 2011). Specifically, alcohol use has been shown to decrease both the quality and quantity of sleep in this population, increase the risk of insomnia, and is also used as a maladaptive coping strategy for those with a psychological disturbance or high levels of stress (Brower, 2003; Conroy et al., 2006; Wong & Fielding, 2011). However, such studies did not employ a sample of clinically depressed individuals. Future research would benefit from including additional predictors of sleep quality, such as various kinds of substance use, other than prescribed medication, to explain sleep quality among people who are clinically depressed.
Conclusions Overall, the present study demonstrated that depressed Chinese males and females experience similar findings to adults from Western countries in the relationship between sleep disturbance and depression. Although our findings demonstrate that demographic variables and depression
DOI: 10.3109/09638237.2014.976856
severity are strong predictors of sleep problems within a nonWestern population, future studies should include other variables consistently found to be associated with both depression and sleep difficulty, such as the use of addictive substances and psychosocial factors.
Acknowledgements The authors would like to acknowledge the assistance of the patients from Shanghai Mental Health Center in completing the questionnaires for the study.
Declaration of interest The authors report no conflicts of interest.
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References Beck AT, Ward CH, Mendelson M, et al. (1961). An inventory for measuring depression. Arch Gen Psychiatry, 4, 561–71. Benca RM, Okawa M, Uchiyama M, et al. (1997). Sleep and mood disorders. Sleep Med Rev, 1, 45–56. Breslau N, Roth T, Rosenthal L, Anreski P. (1996). Sleep disturbance and psychiatric disorders: A longitudinal epidemiological study of young adults. Biol Psychiatry, 39, 411–18. Brower KJ. (2003). Insomnia, alcoholism and relapse. Sleep Med Rev, 7, 523–39. Chen N-H, Johns MW, Li H-Y, et al. (2002). Validation of a Chinese version of the Epworth sleepiness scale. Qual Life Res, 11, 817–21. Chen YF. (2002). Chinese classification of mental disorders (CCMD-3): Towards integration in international classification. Psychopathology, 35, 171–5.
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Conroy DA, Todd AJ, Brower KJ, et al. (2006). Perception of sleep in recovering alcohol-dependant patients with insomnia: Relationship with future drinking. Alcohol, 30, 1992–9. Dew MA, Reynolds CF, Buysse DJ, et al. (1996). Electroencephalographic sleep profiles during depression: Effects of episode duration and other clinical and psychosocial factors in older adults. Arch Gen Psychiatry, 53, 148–56. Ford DE, Cooper-Patrick L. (2001). Sleep disturbances and mood disorders: An epidemiological perspective. Depress Anxiety, 14, 3–6. Ford DE, Kamerow D. (1989). Epidemiological study of sleep disturbances in psychiatric disorders. J Am Med Assoc, 262, 1479–84. Perlis ML, Giles DE, Buysse DJ, et al. (1997). Self-reported sleep disturbance as a prodromal symptom in recurrent depression. J Affect Disorders, 42, 209–12. Perlis ML, Smith LJ, Lyness JM, et al. (2006). Insomnia as a risk factor for onset of depression in the elderly. Behav Sleep Med, 4, 104–13. Rudd D, Rajab H. (1995). Specificity of the Beck Depression Inventory and the confounding role of comorbid disorders in a clinical sample. Cogn Ther Res, 9, 51–68. Sbarra DA, Allen JJB. (2009). Decomposing depression: On the prospective and reciprocal dynamics of mood and sleep disturbances. J Abnorm Psychol, 118, 171–82. Thase ME, Kupfer DJ, Buysse DJ, et al. (1995). Electroencephalographic sleep profiles in single-episode and recurrent unipolar forms of major depression: I. Comparison during acute depressive states. Biol Psychiatry, 38, 506–75. Tsai P-S, Wang S-Y, Wang M-Y, et al. (2005). Psychometric evaluation of the Chinese version of the Pittsburgh Sleep Quality Index (CPSQI) in primary insomnia and control subjects. Qual Life Res, 14, 1943–52. Wong WS, Fielding R. (2011). Prevalence of insomnia among Chinese adults in Hong Kong: A population-based study. J Sleep Res, 20, 117–26. Zeng H, Zeng Y. (1987). The application of the Beck Depression Inventory (BDI) in patients with depression. Chin J Nerv Mental Dis, 4, 236–67.
ISSN: 0963-8237 (Print) 1360-0567 (Online) Journal homepage: http://www.tandfonline.com/loi/ijmh20
Sleep problems among clinically depressed adults in China Sai Zuo, Marita P. McCabe, David Mellor & Yifeng Xu To cite this article: Sai Zuo, Marita P. McCabe, David Mellor & Yifeng Xu (2015) Sleep problems among clinically depressed adults in China, Journal of Mental Health, 24:1, 43-47 To link to this article: http://dx.doi.org/10.3109/09638237.2014.976856
Published online: 30 Dec 2014.
Submit your article to this journal
Article views: 32
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ijmh20 Download by: [Stockholm University Library]
Date: 13 September 2015, At: 04:15
http://informahealthcare.com/jmh ISSN: 0963-8237 (print), 1360-0567 (electronic) J Ment Health, 2015; 24(1): 43–47 ! 2015 Shadowfax Publishing and Informa UK Limited. DOI: 10.3109/09638237.2014.976856
ORIGINAL ARTICLE
Sleep problems among clinically depressed adults in China Sai Zuo1, Marita P. McCabe2, David Mellor2, and Yifeng Xu1 Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China and 2School of Psychology, Deakin University, Melbourne, Victoria, Australia
Downloaded by [Stockholm University Library] at 04:15 13 September 2015
1
Abstract
Keywords
Background: The aim of the study was to explore which variables predict poor sleep among clinically depressed Chinese adults. Methods: In total, 100 participants were recruited from Shanghai Mental Health Centre. The dependent variables were number of hours spent sleeping as well as the quality of sleep and number of times the participants woke during the night. The independent variables were gender, age, length of depression and severity of depression. The use of antipsychotic medication was controlled for in all analyses. Results: The results demonstrated that depression severity was the most important predictor of sleep quality and night waking. Gender and age were also found to be predictors of sleep problems. Conclusions: The findings demonstrated that depressed Chinese patients experienced similar relationships between sleep disturbance and depression to Westerners. Future studies should include other measures of sleep quality as well as variables consistently found to be associated with both depression and sleep difficulty, such as the use of addictive substances and psychosocial factors.
Depression, Chinese, sleep disturbance
Introduction Many depressed individuals report that sleeping problems are the single most debilitating feature of their disorder (Benca et al., 1997). Clinical studies have consistently found that problems with sleep are positively correlated with depressive symptomology, with depressed individuals reporting symptoms, such as difficulty falling asleep at night time, feelings of fatigue during the day, and awakening on multiple occasions throughout the night and in the early morning (Breslau et al., 1996). These symptoms have been profiled using electroencephalographic measurements during numerous clinical studies, which have indicated that the sleep onset latency, number of awakenings, wake after sleep onset and rapid eye movement sleep are increased in sufferers of depression, where total sleep time, sleep efficiency index, slow wave sleep and REMS latency (RL) are reduced (Dew et al., 1996; Thase et al., 1995). Despite the well-established link between sleep disturbance and depressive disorder, their temporal relationship is not easily determined. In unipolar depression, feelings of sadness, guilt, agitation and/or suicide can disrupt sleep onset, interrupt sleep continuity and precipitate early morning or recurrent awakenings. In turn, lack of sleep can maintain Correspondence: Prof. Marita P. McCabe, School of Psychology, Deakin University, 221 Burwood Highway, Burwood, Victoria 3125, Australia. Tel: +61 3 9244 6856. Fax: +61 3 9244 6858. E-mail: marita.mccabe@ deakin.edu.au
History Received 24 October 2012 Revised 5 September 2014 Accepted 2 October 2014 Published online 30 December 2014
depressed mood state and impact the individual’s emotional regulatory abilities, thus further interrupting sleep (Sbarra & Allen, 2009). Research has found that sleep problems can also be a factor that precedes the clinical syndrome (Perlis et al., 1997). For example, even after controlling for a history of depressive symptoms, Breslau et al. (1996) found that prior insomnia was a significant predictor of depressive episodes. Additionally, Perlis et al. (2006) reported that insomnia increased the risk of development of depressive illness. These authors found across nine epidemiological studies, that individuals suffering from persistent sleep problems have a 3.5 times greater likelihood of experiencing a subsequent depressive episode than individuals without such difficulties. This association between sleep disturbance and depression is impacted by a number of other variables. Some of the variance in sleep difficulties found between clinically depressed individuals and controls has been significantly influenced by the participants’ age, with older people being more likely to experience sleep problems regardless of level of depression (Ford & Kamerow, 1989). Dew et al. (1996) stressed that sleep abnormalities are also influenced by the severity of the depressive episode. Their studies indicated that previous depressive episodes, duration of the present episode, type of the current depressive illness, gender and psychosocial stressors are all factors that can significantly impact on the relationship between depression and sleep quality. Most of the above-mentioned studies have focussed on the association between depression and sleep, with
Downloaded by [Stockholm University Library] at 04:15 13 September 2015
44
S. Zuo et al.
Western populations. However, in a sample of 5001 Chinese adults from Hong Kong, Wong & Fielding (2011) found the prevalence rate of insomnia to be 39.4%, with women reporting significantly poorer sleep quality compared to men. Depression was also found to be significantly associated with sleep disturbances. However, little more is known about the relationship between sleep and depression in this nonWestern population. The Wong & Fielding (2011) study examined the association between depression and insomnia alone, and not other aspects of sleep quality. Given this strong association between depression and sleep disturbance among males and females from Western societies, it is argued that further research is needed to explore the factors that impact on this relationship, in a non-Western context. The aim of the present study was to explore which variables significantly predict poor sleep in a sample of Chinese adults. By studying these relationships in a Chinese population, it is possible to determine the generalizability of findings from Western populations. Depression levels, length of time the person has experienced depression and number of depressive episodes were postulated as predictors of various kinds of sleep disturbance. Furthermore, the present study was designed to determine the influence of age and gender differences on sleep quality in depressed Chinese adults.
Methods Participants The sample consisted of 100 participants from an outpatient clinic at Shanghai Mental Health Center, Shanghai, China, ranging in age from 19 to 62 years (comprised of 50 males: M age ¼ 41.94 years, SD ¼ 12.02 and 50 females: M age ¼ 40.64 years, SD ¼ 11.81). Recruitment continued until 50 males and 50 females agreed to participate in the study in order to satisfy power requirements (0.80) for the analyses. The inclusion criteria for participation in the present study was that participants were in the age range of 18–65 and have received a current diagnosis of major depressive disorder using The Chinese Classification of Mental Disorders (CCMD-3) (Chen, 2002). This diagnostic and classification tool has undergone substantial development and validation in China, with 114 psychiatrists from 41 mental health centers and psychiatric hospitals being involved in ensuring its validity and equivalence to the DSM IV (Chen, 2002). Thirty-two out of the 100 participants were receiving oral antipsychotic medication (Clozapine) in treating their depression at the time the study was conducted. All participants were currently receiving SSRI antidepressant medication. Measures Beck Depression Inventory (BDI-1) (Beck et al., 1961). Consisting of 21 items, the BDI-1 is a self-report measure that covers a range of affective, behavioral, cognitive and somatic symptoms thought to be indicative of unipolar depression. Each individual item has a set of four possible answer choices, ranging in intensity and rated on a scale of 0 to 3. Total possible scores range from 0 to 63, with higher scores reflective of increased levels of severity of depressive symptomology. The BDI possesses sound psychometric
J Ment Health, 2015; 24(1): 43–47
properties with high internal consistency reliability (a ¼ 0.89) and associated high levels of concurrent and construct validity (Rudd & Rajab, 1995). In a Chinese population, the BDI has been shown to be reliable and valid, and the internal consistency reliability was found to be 0.85 (Zeng & Zeng, 1987). Participants were asked to indicate the length of time they had suffered from depression in years (i.e. time since first episode of depression), the number of depressive episodes they had experienced, and the number of years they had received treatment. As there were no validated sleep scales in the Chinese language that evaluated the areas that we were targeting, the participants were asked to respond to singleitem questions regarding the following dimensions of sleep quality: the average number of hours of sleep they had per day, the number of times they woke up during sleep and the quality of their sleep in the past seven days (scored or a sevenpoint Likert scale from extremely poor to extremely good). Procedure Ethical approval was received from the Shanghai Mental Health Center. Participants were recruited from the Centre, which is affiliated with the School of Medicine at Shanghai Jiaotong University for 11 months from October 2009 to September 2010. Participants were informed about the study by staff at the Center, staff provided all people diagnosed with depression with a Plain Language Statement and Consent form. Treatment for patients’ depression was not affected by whether or not they participated in the study. The questionnaire (comprising the BDI and questions on sleep) was completed individually by participants and took about 10 min to complete. Analyses All data in the present study were analyzed using SPSS, version 17 (Chicago, IL). Data were screened for missing data, outliers and multicollinearity. Means, standard deviations and ranges for all depression and sleep pattern variables are displayed in Tables 1 and 2, respectively.
Results A series of t-tests were performed on the data to determine if there were any significant differences between males and females across each of the study variables. Results found that there were no significant differences across the variables except for the average number of times they woke up during Table 1. Mean, standard deviation and range of depression variables. Variable
Male M (SD)
Length of depression 5.96 (years) Number of depressive 2.20 episodes Years of treatment 3.24 Depression severity 28.72
Female M (SD)
Total M (SD)
Range
(8.21)
5.08 (5.12)
5.52 (6.94)
0–40
(1.58)
2.52 (1.39)
2.36 (1.49)
1–8
(5.32) 3.31 (5.23) 3.28 (5.25) 0–30 (9.55) 28.72 (7.70) 28.72 (8.63) 14–52
N ¼ 100. Depression severity ¼ Total Beck Depression Inventory (BDI) score.
Sleep problems in China
DOI: 10.3109/09638237.2014.976856
the night, t(99) ¼ 2.03, p50.05 and quality of sleep t(99) ¼ 2.34, p50.05, with females being more likely to wake up during the night and report a lower level of sleep quality compared to males.
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Regression analyses A series of hierarchical regressions were performed to determine which factors were most indicative of sleep quality whilst controlling for the use of antipsychotic medication. In each regression performed, the use of antipsychotic medication by participants did not contribute a significant amount of variance in the target variable. Therefore, whether or not participants were taking antipsychotic medication at the time of testing did not significantly influence the other predictor variables employed in each of the models. In the first regression (Table 3), gender, age, length of time suffering depression, depression severity (as measured by the BDI) and use of antipsychotic medication were employed as predictors of the average number of hours slept in the past 7 days. Results from the regression revealed that these five Table 2. Mean, standard deviation and range of sleep pattern variables.
Variable
Male M (SD)
Female M (SD)
Total M (SD)
Average no. hours slept 6.42 (2.41) 6.84 (2.66) 6.63 (2.53) in past 7 days Times awakened during 2.38 (1.70) 3.10 (1.84) 2.74 (1.80) sleep Sleep quality 3.36 (2.18) 2.44 (1.73) 2.90 (2.01)
Range 2–16 0–10 1–7
N ¼ 100.
45
variables together accounted for 14.7% of the variance explained in average number of hours slept after controlling for the use of antipsychotic medication, F(5, 99) ¼ 3.24, p50.05. Age was the only variable that significantly contributed to this regression, explaining 5.29% of the variance, ¼ 0.05, t ¼ 2.18, p50.05. In this sample, males who were older and reported a greater length of time experiencing depression and depressive symptoms were more likely to report fewer hours slept in the past 7 days. The second regression used the same variables of gender, age, length of depression and depression severity to predict quality of sleep, while controlling for the use of antipsychotic medication (Table 4). After controlling for the use of antipsychotic medication in participants, the total variance explained by this regression model was 45.50%, F(5, 99) ¼ 15.68, p50.001. Gender contributed significantly to the model, ¼ 0.25, t ¼ 3.21, p50.01, accounting for 6.15% of the variance explained in average quality of sleep. Females reporting poorer quality sleep compared to males. Depression severity was the strongest predictor in the regression, explaining 37.30% of the variation in quality of sleep, over and above that explained by the other variables in the model, ¼ 0.61, t ¼ 7.63, p50.001. The results demonstrated that the greater the severity of depression, the poorer the quality of sleep. The final regression employed gender, age, length of depression and depression severity to predict the average number of times the participants woke throughout the night, while controlling for the use of antipsychotic medication (Table 5). After controlling for antipsychotic medication use in participants, the total amount of variance accounted for by the model was 13.90%, F(4, 99) ¼ 3.03, p50.01. Gender was
Table 3. Summary of hierarchical regression analysis predicting the average number of hours slept in the past 7 days controlling for medication. Independent variables Step 1 Use of antipsychotic medication predicting hours slept Step 2 Use of antipsychotic medication Gender Age Length of depression (in years) Depression severity (as measured by the BDI)
B
SE
0.05
0.55
0.01
0.57 0.24 0.05 0.06 0.04
0.57 0.49 0.02 0.04 0.03
0.11 0.05 0.23 0.15 0.14
t 0.10
R2 ¼ 0.00
1.00 0.49 2.18* 1.33 1.43
DR2 ¼ 0.15**
N ¼ 100. *p50.05; **p50.01.
Table 4. Summary of hierarchical regression analysis predicting the sleep quality of depressed Chinese individuals, controlling for medication. Independent variables Step 1 Use of antipsychotic medication predicting sleep quality Step 2 Use of antipsychotic medication Gender Age Length of depression (in years) Depression severity (as measured by the BDI) N ¼ 100. **p50.01; ***p50.001.
B
SE
0.33
0.43
0.08
0.77
0.39 1.00 0.01 0.02 0.14
0.36 0.31 0.01 0.03 0.02
0.09 0.25 0.04 0.08 0.61
1.09 3.21** 0.42 0.85 7.63***
t R2 ¼ 0.07 DR2 ¼ 0.45***
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S. Zuo et al.
J Ment Health, 2015; 24(1): 43–47
Table 5. Summary of hierarchical regression analysis predicting the average number of times participants woke up during the night in depressed Chinese individuals, controlling for medication. B
SE
0.40
0.39
0.10
0.06 0.71 0.01 0.01 0.06
0.41 0.35 0.02 0.03 0.02
0.02 0.20 0.03 0.03 0.31
Independent variables Step 1 Use of antipsychotic medication predicting average number of times awoken during the night Step 2 Use of antipsychotic medication Gender Age Length of depression (in years) Depression severity (as measured by the BDI)
t 1.03
R2 ¼ 0.01
0.15 2.05* 0.30 0.30 3.03**
DR2 ¼ 0.13**
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N ¼ 100. *p50.05, **p50.01.
a significant predictor in the model, explaining 3.96% of variation in the number of times participants woke during the night, with females reporting waking up significantly more often than males, ¼ 0.20, t ¼ 2.05, p50.05. Depression severity was the most significant predictor, explaining 9.30% of the variance in average number of times participants woke up during the night, ¼ 0.31, t ¼ 3.03, p50.01. The results demonstrated that those participants with more severe depression were more likely to wake more frequently.
Discussion The present study aimed to examine the factors that have previously been identified as predictive of sleep disturbances in depressed adults within the context of a Chinese population. It was argued that such data would be valuable in order to ascertain whether the findings reported from western studies could be generalized to populations from other cultural groups. Previous findings within Western populations have found gender and age to be the most relevant demographic variables related to the prevalence of sleep difficulties among depressed people (Breslau et al., 1996; Ford & Kamerow, 1989). Generally, our data were consistent with these findings, with either gender or age being a significant predictor of each of the sleep problems investigated. Specifically, age was the only significant predictor of average number of hours slept among Chinese adults. Furthermore, gender significantly predicted sleep quality and number of times participants woke during the night, with females demonstrated a greater likelihood of suffering from these sleep disturbances. This is comparable to findings from Western populations, which have also found depressed females suffer from sleep disturbance more frequently, and at greater levels compared to males (Breslau et al., 1996; Ford & Cooper-Patrick, 2001; Ford & Kamerow, 1989). Our data are also consistent with the few studies investigating sleep problems in Chinese individuals, which have identified women as experiencing these difficulties more than men (Wong & Fielding, 2011). These findings further demonstrate that demographic variables are important to consider in the relationship between sleep disturbance and depression in a non-Western population. Other than the aforementioned demographic variables, depression severity, as measured by the BDI, was the single
most significant predictor of sleep difficulties in Chinese adults, explaining most of the variation in the regression models predicting sleep quality and number of times participants woke up during the night. These results are not surprising given the strong positive correlation that has consistently been found between these variables in other studies. As length of time suffering depression and use of antipsychotic medication were not significant predictors of any sleep difficulties investigated, the findings suggest that severity of depression is the most important factor to attend to when attempting to alleviate sleeping problems in depressed Chinese adults. Despite these significant findings, other variables that were not investigated in the present study may also impact on the sleep quality experienced by this non-Western population. The predictors of other measures of sleep disturbance, for example, sleep onset latency, napping and/or daytime sleepiness should also be examined. Further scales that have been validated with Chinese populations need to be used in this research. Examples of such scales are the Epworth sleepiness Scale, that measures the level of sleepiness (Chen et al., 2002) and the Pittsburgh Sleep Quality Index that measures insomnia (Tsai et al., 2005). Previous studies within nonWestern contexts have found that unemployment, anxiety, alcohol use, long-term health problems and poor mental health are also positive predictors of sleeping difficulties in Chinese adults (Wong & Fielding, 2011). Specifically, alcohol use has been shown to decrease both the quality and quantity of sleep in this population, increase the risk of insomnia, and is also used as a maladaptive coping strategy for those with a psychological disturbance or high levels of stress (Brower, 2003; Conroy et al., 2006; Wong & Fielding, 2011). However, such studies did not employ a sample of clinically depressed individuals. Future research would benefit from including additional predictors of sleep quality, such as various kinds of substance use, other than prescribed medication, to explain sleep quality among people who are clinically depressed.
Conclusions Overall, the present study demonstrated that depressed Chinese males and females experience similar findings to adults from Western countries in the relationship between sleep disturbance and depression. Although our findings demonstrate that demographic variables and depression
DOI: 10.3109/09638237.2014.976856
severity are strong predictors of sleep problems within a nonWestern population, future studies should include other variables consistently found to be associated with both depression and sleep difficulty, such as the use of addictive substances and psychosocial factors.
Acknowledgements The authors would like to acknowledge the assistance of the patients from Shanghai Mental Health Center in completing the questionnaires for the study.
Declaration of interest The authors report no conflicts of interest.
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