Bipolar disorder is highly under-researched in Africa. Existing studies show that racial/ethnic disparities exist for sleep quality. Poor sleep quality in bipolar disorder causes significant morbidity and mortality even during periods of euthymia.
This study aimed to assess sleep quality and its correlates amongst euthymic patients with bipolar I disorder from Nigeria.
The study was carried out in a teaching hospital, and state hospital, in Ibadan, Nigeria.
This cross-sectional study was conducted amongst 76 euthymic bipolar patients aged between 18 and 60 years, meeting the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) diagnostic criteria for bipolar disorder. Euthymia was defined as having a score of ≤ 5 on the Young Mania Rating Scale and < 8 on the Hamilton Depression Rating Scale. Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI).
A total of 37 (48.7%) participants had poor quality sleep. Sleep quality was associated with marital status (
Poor sleep quality frequently persists during euthymic periods in patients with bipolar disorder. The correlates identified can be targeted for intervention during treatment.
Bipolar disorder is potentially a lifelong episodic and recurrent illness characterised by prominent and persistent mood swings and with a diverse course that can often result in significant distress and impairment in functioning. Sleep disturbances are central to the onset, relapse, recovery, prognosis and outcome of bipolar disorder.
Contrary to previously held assumptions, remission periods (euthymia) in bipolar disorder are not asymptomatic periods. Such euthymic periods are characterised by psychopathologies including sleep disturbances and poor sleep quality. Such psychopathologies and disturbances produce a more severe clinical outcome that considerably affects the quality of life of affected individuals.
Poor sleep quality in bipolar disorder causes substantial medical and psychological morbidities such as reduced global functional ability, relapses, recurrences, neurocognitive impairment and poor prognosis.
Very few studies have been conducted on sleep quality during the euthymic phase of bipolar disorders. Also, very little is known about the correlates and predictors of sleep quality during this period.
Understanding the factors associated with sleep quality during the euthymic phase of bipolar I disorder may play a significant role in improving clinical course and help to negotiate a more favourable outcome for patients with bipolar disorder.
This study aimed to assess sleep quality and its correlates amongst well-characterised euthymic patients with bipolar I disorder.
The Mulberry study is a cross-sectional study comparing sociodemographic and clinical characteristics such as neurocognitive function, psychopathology, sleep, physical activity and spirituality between patients with bipolar disorder, patients with schizophrenia and healthy controls.
While waiting to see their doctors, the research assistants personally invited successive patients attending the outpatient psychiatry clinics of the selected hospitals to participate in the study. The study was explained to them and consent was obtained. The study instruments were administered or a date was scheduled during the succeeding week when a detailed interview could be conducted.
To be eligible for inclusion in the current study, participants had to be euthymic and meet the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) diagnostic criteria for bipolar disorder using the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I). A participant with bipolar disorder was deemed to be euthymic if he or she had a score of ≤ 5 on the Young Mania Rating Scale (YMRS) and had a score of < 8 on the Hamilton Depression Rating Scale (HDRS).
The Pittsburgh Sleep Quality Index (PSQI) is a self-rated questionnaire designed for use in both research and clinical practice. It assesses the quality of sleep and sleep disturbances over a 1-month time interval.
Important sociodemographic and clinical information was obtained from all participants. The participants were also assessed with the following instruments:
The Young Mania Rating Scale (YMRS)
The 17-item Hamilton Depression Rating Scale (HDRS)
The Positive and Negative Syndrome Scale (PANSS)
We carried out data analysis with the Statistical Package for the Social Science (SPSS), version 22.0 for Windows. Categorical variables were summarised using frequencies and proportions. The chi-squared test was used to analyse the relationship between two qualitative variables. Continuous variables were described using means and standard deviation (s.d.) if they were normal in type or using medians and ranges if not normally distributed. An independent sample
The study was conducted following the guidelines laid down in the Declaration of Helsinki. The protocol and procedures were reviewed and approved by the Oyo State Research Ethical Review Committee (AD13/479/746).
A total of 110 participants with a diagnosis of bipolar I disorder were recruited into the study, however, only 76 met the criteria for euthymia. The 76 participants (47 females, 29 male) were subsequently included in the current analysis. The mean age was 39.09 ± 11.10 years. A total of 37 (48.7%) participants had poor quality sleep during the past 1 month. There was no significant difference in socio-demographic and clinical characteristics between the group with poor sleep quality and the group with good sleep quality except for marital status and lifetime suicidal plan. A significantly higher proportion of the participants who had poor sleep quality were single or never married compared to those with good sleep quality (43.2% vs. 26.3%
The sociodemographic and clinical characteristics of participants and comparison of clinical features of bipolar disease according to Pittsburgh Sleep Quality Index scores.
Characteristics | Mean ± s.d. | Range | Mdn | PSQI ≤ 5 ( |
Range | Mdn | PSQI > 5 ( |
Range | Mdn | |
---|---|---|---|---|---|---|---|---|---|---|
Age of patient (years) | 39.09 ± 11.10 | - | - | 39.67 ± 11.11 | - | - | 38.49 ± 11.20 | - | - | 0.646 |
Age at onset of first mood disorder episode (years) | 27.66 ± 9.65 | - | - | 28.03 ± 10.80 | - | - | 27.26 ± 8.34 | - | - | 0.731 |
Average length of episode (weeks) | 4.07 ± 11.17 | 0–96.00 | 2.00 | 3.13 ± 3.76 | 0–24.00 | 3.00 | 5.09 ± 15.70 | 0–96.00 | 2.00 | 0.523 |
Average time between episodes (years) | 2.80 ± 2.89 | 0–20.00 | 2.00 | 3.02 ± 3.57 | 0–20.00 | 2.00 | 2.59 ± 2.00 | 0–9.00 | 2.25 | 0.529 |
Numbers of years of education (years) | 14.70 ± 2.57 | 14.56 ± 3.06 | - | - | 14.84 ± 1.95 | 0.645 | ||||
Mood stabiliser dose (mg/day) (Carbamazepine equivalents) | 175.05 ± 277.64 | 0–1000.00 | 0.00 | 120.61 ± 231.85 | 0–800.00 | 0.00 | 232.43 ± 311.85 | 0–1000.00 | 0.00 | 0.149 |
Antipsychotic dose (mg/day) (haloperidol equivalents) | 7.50 ± 45.76 | 0–400.00 | 0.17 | 2.16 ± 3.11 | 0–11.68 | 0.33 | 13.13 ± 65.49 | 0–400.00 | 0.03 | 0.970 |
Number of episodes | 3.89 ± 3.17 | - | - | 4.00 ± 3.48 | - | - | 3.78 ± 2.83 | - | - | 0.764 |
PANSS (Positive subscale) | 8.80 ± 2.65 | - | - | 8.74 ± 2.04 | - | - | 8.86 ± 3.19 | - | - | 0.843 |
PANSS (Negative subscale) | 9.61 ± 3.28 | - | - | 9.74 ± 3.22 | - | - | 9.46 ± 3.27 | - | - | 0.708 |
PANSS (General subscale) | 19.36 ± 3.79 | - | - | 19.56 ± 4.34 | - | - | 19.14 ± 3.16 | - | - | 0.625 |
PANSS (Total score) | 37.76 ± 6.52 | - | - | 38.05 ± 7.16 | - | - | 37.46 ± 5.85 | - | - | 0.695 |
YMRS* total score | 1.99 ± 2.42 | - | - | 1.87 ± 2.47 | - | - | 2.10 ± 2.38 | - | - | 0.673 |
HDRS@ total score | 3.03 ± 2.13 | - | - | 2.87 ± 2.12 | - | - | 3.19 ± 2.15 | - | - | 0.520 |
SOFAS*** score | 61.76 ± 12.46 | - | - | 63.13 ± 13.45 | - | - | 60.28 ± 11.29 | - | - | 0.326 |
BMI** | 27.03 ± 7.77 | - | - | 27.31 ± 5.90 | - | - | 26.74 ± 9.42 | - | - | 0.753 |
Monthly income (₦) Naira | 46 389 ± 71 060 | 0–403 000 | 20 000 | 33 026 ± 36 189 | 0–150 000 | 22 500 | 61 323 ± 94 658 | 0–403 000 | 20 000 | 0.409 |
Net worth (₦) Naira | 347 486 ± 913 692 | 0–5 000 000 | 30 000 | 310 236 ± 837 175 | 0–5 000 000 | 50 000 | 386 805 ± 998 606 | 5000–5 000 000 | 20 000 | 0.987 |
SOFAS, Social and Occupational Functioning Assessment Scale; HDRS, Hamilton Rating Scale for Depression; PANSS, Positive and Negative Syndrome Scale; YMRS, Young Mania Rating Scale; BMI, Body Mass Index; Fishers, Fisher Exact Test; PSQI, Pittsburgh Sleep Quality Index; MWW, Mann-Whitney U test; s.d., standard deviation.
The sociodemographic and clinical characteristics of participants and comparison of clinical features of bipolar disease according to Pittsburgh Sleep Quality Index scores.
Characteristics | % | PSQI |
PSQI ≤ 5 |
||||
---|---|---|---|---|---|---|---|
% | % | ||||||
Male | 29 | 38.2 | 13 | 33.3 | 16 | 43.2 | 0.374 |
Female | 47 | 61.8 | 26 | 66.7 | 21 | 58.6 | - |
Employed | 64 | 84.2 | 32 | 82.1 | 32 | 86.5 | 0.596 |
Unemployed | 12 | 15.8 | 7 | 17.9 | 5 | 13.5 | - |
Single/Never married | 26 | 34.2 | 10 | 26.3 | 16 | 43.2 | |
Married/cohabiting | 42 | 55.3 | 21 | 55.3 | 21 | 56.8 | - |
Divorced/widowed/separated | 7 | 9.2 | 7 | 18.4 | 0 | 0.0 | - |
No | 53 | 69.7 | 27 | 69.2 | 26 | 70.3 | 0.921 |
Yes | 23 | 30.3 | 12 | 30.8 | 11 | 29.7 | - |
Typical antipsychotic | 27 | 35.5 | 16 | 64.0 | 9 | 36.0 | 0.425 |
Atypical antipsychotic | 19 | 25.0 | 11 | 52.4 | 10 | 47.6 | - |
No | 53 | 69.7 | 28 | 71.8 | 25 | 67.6 | 0.688 |
Yes | 23 | 30.3 | 11 | 28.2 | 12 | 32.4 | - |
No | 64 | 84.2 | 36 | 92.3 | 28 | 75.7 | |
Yes | 12 | 15.8 | 3 | 7.7 | 9 | 24.3 | - |
No | 71 | 93.4 | 37 | 94.9 | 34 | 91.9 | 0.671 (Fishers) |
Yes | 5 | 6.6 | 2 | 5.1 | 3 | 8.1 | - |
Absent | 75 | 98.7 | 38 | 97.4 | 1 | 2.6 | 1.000 (Fishers) |
Present | 1 | 1.3 | 37 | 100.0 | 0 | 0.0 | - |
Present | 10 | 13.2 | 34 | 87.2 | 32 | 86.5 | 0.929 |
Absent | 66 | 86.8 | 5 | 12.8 | 5 | 13.5 | - |
Note: Bold indicates
Although the differences were not statistically significant, participants with poor sleep quality had a higher average length of an episode, used higher doses of mood stabiliser and antipsychotics per day, had lower social and occupational functioning, lower monthly income and financial net worth than participants with good sleep quality (
Participants with good quality sleep did significantly better than those with poor quality sleep in the seven components of the PQSI except for habitual sleep efficiency (Component 4) and sleep disturbances (Component 5). Therefore, participants with good sleep quality had higher total sleep duration, lower time to fall asleep (sleep latency), better subjective quality of sleep, were less likely to use sleep medications and had less daytime dysfunction than participants with poor sleep quality (see
Characteristics of sleep quality in bipolar patients.
Characteristics | Mean ± s.d. | Range | Median | PSQI ≤ 5 ( |
Range | Median | PSQI > 5 ( |
Range | Median | |
---|---|---|---|---|---|---|---|---|---|---|
Total sleep time (Hours) | 8.19 ± 1.57 | - | - | 9.21 ± 1.09 | - | - | 7.65 ± 1.80 | - | - | |
Time to fall asleep (Sleep latency, minutes) | 20.24 ± 16.50 | - | - | 15.49 ± 10.97 | - | - | 25.24 ± 19.74 | - | - | |
Habitual sleep efficiency (%) | 97.54 ± 7.77 | - | - | 98.31 ± 3.34 | - | - | 96.74 ± 10.62 | - | - | 0.395 |
- | - | - | - | - | - | |||||
Subjective quality of sleep | 0.36 ± 0.60 | 0–3.00 | 0.00 | 0.10 ± 0.31 | 0–1.00 | 0.00 | 0.62 ± 0.72 | 0–3.00 | 1.00 | |
Sleep disturbances | 0.62 ± 0.49 | - | - | 0.60 ± 0.59 | - | - | 0.64 ± 0.49 | - | - | 0.682 |
Use of sleep medication | 1.66 ± 1.46 | - | - | 0.77 ± 1.33 | - | - | 2.59 ± 0.90 | - | - | |
Daytime dysfunction | 0.49 ± 0.79 | 0–3.00 | 0.00 | 0.15 ± 0.37 | 0–1.00 | 0.00 | 0.84 ± 0.96 | 0–3.00 | 1.00 | |
PSQI global score | 4.49 ± 2.85 | - | - | 2.28 ± 1.38 | - | - | 6.81 ± 2.04 | - | - |
Note: Bold indicates
PSQI, Pittsburgh Sleep Quality Index.
Characteristics of sleep quality in bipolar patients.
Characteristics | % | PSQI ≤ 5 |
PSQI > 5 |
||||
---|---|---|---|---|---|---|---|
% | % | ||||||
No | 32 | 42.1 | 29 | 74.4 | 3 | 8.1 | |
Yes | 44 | 57.9 | 10 | 25.6 | 34 | 91.9 | - |
Good | 73 | 96 | 39 | 100 | 0 | 0.0 | 0.111 (Fishers) |
Bad | 3 | 4 | 34 | 91.9 | 3 | 8.1 | - |
No | 51 | 67.1 | 33 | 84.6 | 18 | 48.6 | |
Yes | 25 | 32.9 | 6 | 15.4 | 19 | 51.4 | - |
Adequate | 72 | 94.7 | 39 | 100.0 | 0 | 0.00 | 0.051 (Fishers) |
Inadequate | 4 | 5.3 | 33 | 89.2 | 4 | 10.8 | - |
Note: Bold indicates
PSQI, Pittsburgh Sleep Quality Index.
Binary logistic regression analysis to determine the factors that were independently associated with poor sleep quality in euthymic bipolar disorder patients indicated that subjective quality of sleep, use of sleep medication, daytime dysfunction were independently associated with poor sleep quality (see
Binary logistic regression analysis to determine factors independently associated with poor sleep quality in euthymic bipolar disorder patients.
Characteristics | OR | 95% CI for OR |
||
---|---|---|---|---|
Lower | Upper | |||
Married/cohabiting | 1.60 | 0.18 | 0.59 | 4.32 |
Divorced/widowed/separated | 0.19 | 0.07 | 0.02 | 1.77 |
Single/Never married | 1 | - | - | - |
No | 1.80 | 0.745 | 0.05 | 61.66 |
Yes | 1 | - | - | - |
Time to fall asleep (Sleep latency, minutes) | 1.09 | 0.150 | 0.97 | 1.22 |
Total sleep time (Hours) | 0.99 | 0.094 | 0.97 | 1.00 |
Subjective quality of sleep | 60.08 | 1.10 | 3289.47 | |
Use of sleep medication | 13.36 | 2.03 | 88.05 | |
Daytime dysfunction | 16.23 | 1.09 | 241.63 |
Note: Bold indicates
Nearly half (48.7%) of the euthymic bipolar I patients had poor sleep quality suggesting that many euthymic patients with bipolar disorder display substantial disturbance in sleep quality during remission. This means that about half the population of bipolar disorder patients purportedly in remission are at the risk of neurocognitive impairment, low immunity, obesity, heart disease, diabetes, infertility, poor social and occupational functioning and other effects of poor sleep quality because of impaired sleep quality.
We found that a significantly higher proportion of the participants who had poor sleep quality were single or never married compared to those with good sleep quality. This is in keeping with existing studies showing that poorer sleep quality is more commonly associated with unpartnered relationship status (single, divorced, cohabiting, widowed) than partnered relationship status (i.e. married or cohabiting).
We found a significant association between sleep quality and a suicidal plan. This is in keeping with existing studies that found an association between suicidal behaviours and impaired quality of sleep amongst euthymic bipolar patients.
Furthermore in males, poor sleep quality is associated with suicide attempts, but not in females. This implies that there may be sex differences in the relationship between disturbed sleep quality and suicidal behaviour. Testosterone levels and age have been implicated in this phenomenon.
The mean sleep latency in participants with poor sleep quality in our study (25 min) was significantly higher than that for participants with good sleep quality (15 min). Additionally, it was higher than the normal 10–20 min usually found in adults. The findings regarding sleep latency are in parity with existing reports that indicate that euthymic bipolar patients have longer sleep-onset latency than during manic or depressive episodes.
We found evidence of a significant association between poor sleep quality and subjective quality of sleep, use of sleep medication and daytime dysfunction amongst euthymic patients with bipolar disorder. Notably, these associations remained significant after controlling for several covariates in binary logistic regression.
The finding that daytime dysfunction was independently associated with euthymic bipolar patients replicates the report on sleep by Geoffroy et al. conducted amongst euthymic bipolar disorder patients and healthy controls. The authors found poorer sleep efficiency, frequent sleep disturbances and daytime dysfunction to be associated with euthymic bipolar disorder.
Poor sleep quality in euthymic bipolar disorder patients was independently associated with medication use. This is in keeping with existing studies showing that euthymic patients with bipolar disorder are more likely to use sleep medications compared to healthy controls.
There were certain limitations to this study. First is the use of PSQI which is both subjective and retrospective and may be laden with the problem of recall bias. Second, the PSQI generates a global score from its seven component scores. These components are influenced by many factors. Third, the sample size was small; this may have reduced the power of the study to detect significant differences.
Amongst euthymic bipolar patients, poor sleep quality frequently persists during euthymic periods and can be a focus of targeted intervention. An assessment of sleep quality should be routinely carried out in the assessment of euthymic bipolar patients.
The Mulberry study was funded by the Tertiary Education Trust Fund (TETFUND).
O.E. contributed to the conceptualisation, methodology, supervision, writing, reviewing and editing of the article. A.F-T. contributed to the methodology, writing, original draft preparation and reviewing of the final manuscript.
This work was supported by a grant from the Tertiary Education Trust Fund (TETFUND). The funder did not play any role in the design, collection, screening, interpretation, writing, and submission for publication of this study. The funder holds no responsibility for the contents of this study.
Data that support the findings of this study are available from the corresponding author, O.E., upon reasonable request.
The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of any affiliated agency of the authors.