Discrepancy between subjective and objective sleep in patients with depression

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1 PCN Psychiatric and Clinical Neurosciences Blackwell Science Pty Ltd 573June Subjective and objective sleep K. Tsuchiyama et al /j x Original Article259264BEES SGML Psychiatry and Clinical Neurosciences (2003), 57, Regular Article Discrepancy between subjective and objective sleep in patients with depression KOUNOSUKE TSUCHIYAMA, MD, HARUO NAGAYAMA, MD, PhD, KIYOMI KUDO, MD, KATSUHIRO KOJIMA, MD AND KUMIKO YAMADA, MD Department of Neuropsychiatry, Oita Medical University, Hasama-machi, Oita, Japan Abstract The literature investigating the relationship between objective and subjective sleep in depressed patients is limited and the results are inconsistent. Furthermore, many factors that influence the aforementioned relationship have not been investigated. The present study was carried out to clarify the characteristics of self-estimation of sleep in depressed patients. Sleep was estimated concurrently using a sleep log and polysomnography for 5 consecutive days to investigate the relationship between subjective sleep estimation and objective sleep estimation in 23 patients with major depression (Diagnostic and Statistical Manual of Mental Disorders, 3rd edn, revised; DSM- III-R). Factors related to a discrepancy between both types of estimation were identified. The subjective total sleep time showed a significant, but moderate, positive correlation (correlation coefficient: 0.63) with the objective total sleep time. The degree of discrepancy was significantly correlated with various objective sleep variables and severity of depression. In the underestimation group in which the subjective total sleep time was shorter than the objective total sleep time, the objective total sleep time and slow-wave sleep time were shorter, age was greater and the extroversion score (Maudsley Personality Inventory) was lower than in the overestimation group in which the subjective total sleep time was longer than the objective total sleep time. The data suggest that subjective sleep estimation in depressed patients is influenced by their objective sleep, severity of depression, age and personality. Key words major depression, Maudsley Personality Inventory, polysomnography, sleep, sleep log. INTRODUCTION Sleep disorder is a common symptom of depression and is considered to be an important parameter in the Diagnostic and Statistical Manual of Mental Disorders (DSM) diagnostic system and in the scales for depression such as Hamilton Rating Scale for Depression (HRSD). 1 However, in clinical practice, sleep is usually estimated subjectively by patients themselves. While sleep may also be estimated by other persons, including family and medical staff, objective estimation by polysomnography (PSG) is rare. The PSG recordings obtained for research purposes in depressed patients show prolonged sleep latency, shortened rapid eye Correspondence address: Dr Kounosuke Tsuchiyama, Department of Neuropsychiatry, Tsurumi Hospital, 4333 Tsurumi, Beppu, Oita , Japan. tsuchi@oita-med.ac.jp Received 3 April 2002; revised 27 November 2002; accepted 1 December Regular Article movement (REM) latency, decreased slow-wave sleep, and increased wakefulness in depressed patients. 2 5 There have been a few studies investigating the relationship between subjective sleep estimation by patients and objective sleep variables determined by PSG in depressed patients. However, the results of these studies are inconsistent. One study showed that depressed patients could not accurately estimate their sleep time 6, while another study showed that depressed patients could estimate it considerably accurately. 7 Furthermore, there is only limited literature investigating the factors that contribute to discrepancies between subjective and objective sleep estimations. To clarify characteristics of subjective sleep estimation in depressed patients, we investigated the relationship between subjective sleep estimation based on sleep logs and objective sleep estimation by PSG. We also assessed the influence of age, personality, and severity of depression on the degree of discrepancy between subjective and objective sleep estimation.

2 260 K. Tsuchiyama et al. METHODS Subjects The subjects were 23 depressed patients who were consecutively admitted to the Department of Neuropsychiatry, Oita Medical University. The inclusion criteria for this study included a current episode of major depression (DSM-III-R); age of between 18 and 65 years; patient diagnosis made separately by two psychiatrists; no psychotropic drugs for at least 2 weeks prior to initiation of the present study; and written informed consent to participate in the study. Patients were excluded from the study if they had a clear physical disorder, intoxication disorder, cerebral injury or disorder with a significant influence on metabolism (including cardiovascular, hepatic, renal and endocrine systems) or the function of the brain. Patients requiring drug therapy, pregnant women, patients with mental retardation, patients with severe speech disorders, patients with impaired hearing and patients at a high risk for attempting suicide were also excluded from the study. The study was approved by the Ethical Committee of Oita Medical University. Study design A placebo that was indistinguishable from clomipramine in appearance was administered on days 2 7 of hospital admission. Clomipramine was administered once daily at noon at a dose of 75 mg from days 8 to 10 and at a dose of 150 mg from day 11 through 36. The severity of depression was evaluated according to the 17-item HRSD between 09:00 hours and 11:30 hours on days 1, 3 and 8. On hospital admission the mean HRSD score was 21.7 (SD = 5.3). The mean HRSD score on days 3 and 8 was used for analysis for the relationship between sleep and HRSD. Patients also completed the Maudsley Personality Inventory (MPI). 8 To minimize the influence of symptoms, the MPI was administered on day 36 when symptoms had almost gone into remission. The mean HRSD on day 36 was 9.0 (SD = 7.5). The mean age was 38.1 years (SD = 11.2 years) and the number of men and women was 15 and eight, respectively. Objective sleep variables The PSG was performed after the evening meal from 19:00 hours until the time the patient rose the next morning for 5 consecutive days from days 3 to 8 while a placebo was administered. The patients were informed that they would receive no active drugs during PSG study. The patients were allowed to move freely on the room and ward and to determine freely the time of going to bed or that of getting up. Meals began at 08:00, 12:00, and 18:00 hours. The PSG recordings were obtained using a telemeter in another room so that sleep could be recorded during free daily life. Polysomnography consisted of two channels of electroencephalography recording (C3-A2, C4-A1), bilateral electro-oculograms (referenced to A1) and bipolar chin electromyograms. The paper speed was set at 15 mm/s and the stage of sleep was determined visually for every page (20 s) according to the criteria of Rechtshaffen and Kales. 9 The sleep variables analyzed were total sleep time; waking after sleep onset; percentage of waking after sleep onset to total sleep time; duration of each sleep stage (stages 1 and 2, slow-wave sleep, REM sleep); percentage of each sleep stage (stages 1 and 2, slow-wave sleep, REM sleep) to total sleep time; and REM latency (time from the onset of sleep to the appearance of the first REM sleep). Data on the sleep variables obtained in the first night were excluded and mean values in the second to fifth nights were used for analysis. Subjective sleep variables The patients were asked to keep a sleep log for 5 days from day 3 to day 8 while a placebo was administered. Each log contained 144 small squares each representing 10 min of a 24-h period. All patients had their own watch and/or clock. The depth of sleep was classified into three stages: lying in bed but wakeful ; dozing in bed (light sleep); and sound sleep in bed (deep sleep). The sum of light or deep sleep time per night was calculated as the subjective total light or deep sleep time, respectively, and the sum of the two was calculated as the subjective total sleep time. Mean values in the second to fifth nights were used for analysis. Statistical analysis Statistical analysis was performed using Spearman s rank correlation coefficient, the Mann Whitney U-test and Fisher s exact probability test. The level of significance was P < RESULTS Sleep variables based on sleep logs and polysomnography In the calculation of mean values of sleep variables according to sleep logs, the subjective total sleep time, deep sleep time and light sleep time were 419.6, and min, respectively. The mean values of the time lying bed but wakeful and waking after sleep

3 Subjective and objective sleep 261 Table 1. Sleep variables via PSG Mean ± SD Total sleep time (min) ± 76.6 REM latency (min) 83.2 ± 56.1 Waking after sleep onset (min) 68.8 ± 47.5 % stage ± 0.1 % stage ± 0.1 % slow-wave sleep 4.8 ± 0 % REM sleep 20.3 ± 0.1 % waking after sleep onset 18.9 ± 15.7 PSG, polysomnography; REM, rapid eye movement. onset according to sleep logs were min (SD = min) and 7.4 min (SD = 11.7 min), respectively. Table 1 shows the mean values of sleep variables obtained by PSG. The total sleep time, waking after sleep onset and percentage slow-wave sleep time were min, 68.8 min and 4.8%, respectively. The REM latency was 83.2 min and shortened REM latency (<60 min) was noted in five of 23 patients (21.7%). Figure. 1. Relationship between objective and subjective total sleep times. Correlation between subjective and objective sleep times A significant positive correlation (R = 0.63; P < 0.005) was noted between the subjective total sleep time and the objective total sleep time (Fig. 1). The subjective total deep sleep time was positively correlated with the objective total sleep time (R = 0.427; P < 0.05) and percentage slow-wave sleep time (R = 0.470; P < 0.05), and negatively correlated with percentage of time awake after sleep onset (R =-0.435; P < 0.05). No significant correlation was found between the subjective total light sleep time and stage 1 time. No significant correlation was found between the subjective wake time after sleep onset and the objective wake time after sleep onset. Difference between subjective and objective total sleep times To determine the degree of discrepancy between the subjective and objective total sleep times, the objective total sleep time was subtracted from the subjective total sleep time. The average during 4 days was calculated (Fig. 2). The discrepancy between both total sleep times showed a significant positive correlation with percentage slow-wave sleep (R = 0.50; P < 0.05) but was not significantly correlated with other variables Figure. 2. Difference distribution between subjective and objective total sleep time. obtained by PSG. The following results were obtained when the absolute value of discrepancy between both total sleep times was investigated for a correlation with each variable of PSG and total HRSD. The absolute value of discrepancy between both total sleep times showed a positive correlation with percentage stage 1 sleep (R = 0.60; P < 0.005), time awake after sleep onset

4 262 K. Tsuchiyama et al. Table 2. Comparison between the underestimation and overestimation groups Underestimation group n = 9 Overestimation group n = 14 P Total sleep time (min; mean ± SD) ± ± Slow-wave sleep time (min; mean ± SD) 7.9 ± ± % slow-wave sleep (mean ± SD) 1.8 ± ± Age (years; mean ± SD) 43.6 ± ± Score for extroversion (MPI; mean ± SD) 14.4 ± ± HRSD (mean ± SD) 18.3 ± ± Sex ratio (male: female) 8:1 7: MPI, Maudsley Personality Inventory; HRSD, Hamilton Rating Scale for Depression. (R = 0.57; P < 0.005) and HRSD (R = 0.53; P < 0.01) and a negative correlation with percentage slow-wave sleep (R =-0.43; P < 0.05). Nine patients (39.1%) were classified into the underestimation group, in which the subjective total sleep time was shorter than the objective total sleep time, while 14 patients (60.9%) were classified in the overestimation group in which the subjective total sleep time was longer than the objective total sleep time. Eighteen patients (78%) showed an at least 30-min overestimation or underestimation. The objective total sleep time and slow-wave sleep time were 16.1% (P < 0.05) and 73.3% (P < 0.005) shorter, respectively, and percentage slow-wave sleep was 73.5% (P < 0.01) lower in the underestimation group than in the overestimation group. The age of patients was 9 years greater in the underestimation group than in the overestimation group (P < 0.05). The MPI score for extroversion was 51.7% lower in the underestimate group than in the overestimate group (P < 0.05). The score for neuroticism, HRSD and sex ratio showed no significant difference between the two groups (Table 2). DISCUSSION Although a significant positive correlation was noted between the subjective and objective total sleep times, the correlation coefficient was 0.63 and was not convincingly high. Moreover, the discrepancy between the two reports was 30 min in 78% and 1h in 52% of patients. Thus, it appears that the depressed patients did not necessarily estimate their sleep time accurately. Studies on the relationship between subjective and objective sleep times have been carried out mainly in patients with insomnia, and the literature is sparse on such studies in depressed patients. Weiss et al. concluded that depressed patients tended to estimate their sleep time inaccurately, because only one of seven inpatients with depression could accurately estimate his sleep time. 6 In contrast, Armitage et al., who investigated outpatients, concluded that depressed patients as well as healthy persons could estimate their sleep time considerably accurately. 7 Their opposed conclusions may be explained by the results of the present study in that the degree of inaccurate subjective sleep estimation increases with increasing severity of depression. Patients with mild depression who can be treated on an outpatient basis may be able to estimate their sleep relatively accurately while patients with severe depression requiring hospital admission may estimate their sleep inaccurately. Our data suggest that objective sleep as well as the severity of depression influence self-estimation of total sleep time. The degree of inaccurate estimation increased with decreases in the depth of sleep and increases in the time of wakefulness. In other words, the degree of inaccurate subjective sleep estimation in depressed patients increased in accordance with the severity of objective sleep disturbances. To our knowledge, this is the first report of this problem in depressed patients. Based on the type of inaccuracy in subjective sleep estimation, we classified depressed patients into two opposite groups: underestimation and overestimation groups in which their sleep time was estimated to be shorter and longer than the actual sleep time, respectively. In general it is believed that depressed patients underestimate their sleep duration. However, our results do not support such a belief: some depressed patients underestimated their sleep duration while others overestimated sleep duration. Our results were consistent with the reports of Edinger and Fins, 11 Rotenberg et al. 14 and Vanable et al. 13 but inconsistent with the report of Armitage et al. 7 Edinger and Fins investigated the distribution of sleep time misperceptions in 56 depressed patients. 11 The percentage of patients who underestimated sleep

5 Subjective and objective sleep 263 duration and the percentage of patients who overestimated sleep duration were almost equal. Rotenberg et al. investigated the relationship between subjective sleep estimation and objective sleep variables in 30 depressed patients. 14 The underestimation of sleep duration was present in 42% of all nights. The overestimation was present in 33% of all nights. Vanable et al. reported sleep duration estimates in 11 insomniacs with depressive disorder. 13 They calculated subjective sleep ratio score (estimated sleep time/ PSG sleep time). The mean of the subjective sleep ratio score was 92.3 but SD was Then it was suggested that some depressed patients underestimated sleep duration, others overestimated sleep duration. Armitage et al. investigated the relationship between objective and subjective sleep measures in 52 depressed outpatients. 7 The majority of patients underestimated total sleep time. The difference of age and the severity of sleep disturbances of the patients could probably account for the inconsistency with the report of Armitage et al. 7 Precise investigation of the characteristics of underestimation and overestimation groups showed a number of differences between the groups. Specifically, total sleep time was shorter and the depth of sleep was less in objective sleep estimation and deep sleep time was shorter in subjective sleep estimation in the underestimation group, compared to the overestimation group. Furthermore, age was greater and the extroversion score was lower in the underestimation group compared to the overestimate group. To our knowledge, the literature includes only one report on the influence of personality on the subjective estimation of sleep time, indicating that specific factors of the Minnesota Multiphasic Personality Inventory (MMPI) had an influence on sleep time estimation in patients with sleep disorder. 13 No such effects, however, have been reported in depressed patients. The influence of age on the subjective estimation of sleep time was reported in patients with sleep disorder 11 and obstructive sleep apnea. 15 Both of these reports concluded that subjective estimation of sleep time is not influenced by age. However, there have been no such reports in depressed patients. The results of sleep time estimation in normal controls were inconsistent. Armitage et al. reported the relationship between objective sleep measures in 48 healthy controls. Of normal controls, 58% of men and 56% of women estimated total sleep time within 15 min. Rotenberg et al. reported the relationship between subjective sleep estimation and objective sleep variables in 10 healthy controls. The correct estimation of sleep duration was present in 25% of all nights. Underestimation was present in 55% of all nights; overestimation was present in 20% of all nights. Therefore further study will be needed to investigate the relationship between subjective sleep estimation and objective sleep variables in normal controls. In summary, our data suggest that depressed patients tend to estimate their sleep inaccurately and that this inaccurate estimation is influenced by degree of objective sleep disturbance and severity of depression. Depressed patients estimate their sleep time to be shorter or longer than the actual sleep time. These sleep time misperceptions are influenced by age and personality. 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