Keywords:
stroke - sleep - surveys and questionnaires
Palavras-chave:
acidente vascular cerebral - sono - inquéritos e questionários
Sleep quality influences health and poor quality of sleep can worsen clinical conditions and impair treatment and rehabilitation in stroke patients[1],[2],[3]. The impact of poor sleep quality in prevalent diseases such as stroke is enormous[4],[5],[6].
Sleep-related respiratory disturbances after stroke are very common (40-80%)[7]. They frequently worsen neurologic recovery and impair quality of life[8],[9]. Sleep-related respiratory disturbances are independent risk factors for new strokes, as well as other cardiovascular events. The main sleep-related respiratory disturbance is obstructive sleep apnea, which is characterized by repeated interruption of ventilation during sleep due to pharyngeal airway closure with consequent sleep fragmentation and intermittent hypoxia. Obstructive sleep apnea is correlated with hypertension, diabetes, obesity, stroke, heart attack and a higher incidence of death[4],[10],[11]. The prevalence of obstructive sleep apnea is three-to-four times higher in patients after a stroke[12].
The high cost and prevalence of stroke associated with a greater frequency of sleep disorders justify efforts to determine the best option to identify this overlap. The diagnosis and treatment of sleep disorders is a field that has expanded considerably over recent years.
Unfortunately, the traditional investigation of sleep disturbance is expensive and complicated. This makes it impossible to perform sleep studies for the major portion of stroke patients, in almost all parts of world. However, the physical and cognitive impairment of stroke patients with sleep disorders always needs to be considered in the clinical approach[2],[13]. Thus, cheaper and easier-to-use tools have been created to identify sleep quality and sleep disturbances in patients after stroke - namely, the Pittsburgh Sleep Quality Index (PSQI) and the sleep apnea screening questionnaire - STOP-BANG[14],[15].
The PSQI is the most complete questionnaire for determining sleep quality, with seven components: subjective sleep quality, latency, duration, efficiency, sleep disorders, use of sleep medication and daytime dysfunction. Part of the PSQI covers sleep-related respiratory disturbances; however, it is frequently not used in clinical practice due its length. For an exclusively sleep-related respiratory disturbance investigation, the STOP-BANG can be used. This questionnaire is easier to use in clinical practice[15],[16].
The aim of this study was to describe the scores of the STOP-BANG questionnaire in patients after stroke and correlate the findings with sleep quality measured by the PSQI.
METHODS
Sample and ethics
Seventy-five patients who had had a stroke (ischemic and hemorrhagic) within the last year, over 18 years of age, who attended the Neurovascular Clinic of the Universidade Federal de São Paulo (UNIFESP) consecutively, between March and June 2016, were invited to participate. This study was reviewed and approved by the Institutional Research Ethics Committee of UNIFESP (CAAE: 55362516.6.0000.5505).
The study exclusion criteria were: 1) patients younger than 18 years old; 2) uncontrolled psychiatric illness; 3) confusion or severe cognitive impairment; 4) aphasia; 5) use of sedative or hypnotic medications and 6) more than one year after stroke event. Seven patients were excluded: five patients due to aphasia and two patients due to dementia. Informed consent was obtained from all 68 patients studied.
Study design
This was a cross-sectional, observational study, in a single center - the Department of Neurology, Neurovascular Clinic of UNIFESP. Every assessment was made by filling out forms and questionnaires with the patient.
Demographic characteristics (age and gender), anthropometric features (weight, height, body mass index (BMI), and a measurement of neck circumference, and clinical characteristics (smoking status, diagnosis of systemic arterial hypertension, diabetes mellitus and restless legs syndrome) were obtained. Systemic arterial hypertension was defined as a systolic blood pressure of 140 mm/Hg or higher or a diastolic blood pressure of 90 mm/Hg or higher, or regular use of antihypertensive medication. Diabetes mellitus was defined as a fasting blood glucose concentration of 126 mg/dl or higher or current use of antidiabetic medication. Restless legs syndrome was defined based on International Restless Legs Syndrome Study Group consensus criteria[17].
The clinical characteristics of stroke; neurological impairment score on the National Institutes of Health Stroke Scale (NIHSS); etiologic classification according Trial of Org 10172 in Acute Stroke Treatment (TOAST), validated in Brazil; and evaluation of the degree of disability according to the modified Rankin Scale (mRS) were noted[18],[19],[20].
All patients answered the PSQI and STOP-BANG questionnaires, validated in Brazil[14],[15],[21],[22],[23],[24].
Statistical analysis
Data analysis was performed using the SPSS 15.0 (Statistical Package for Social Science Software), considering a significance level of less than 5% for all statistical tests.
Data were expressed as mean and standard deviation: age, BMI, NIHSS, mRS, STOP-BANG, and PSQI. We determined the prevalence of arterial hypertension, diabetes mellitus, current smoking, restless legs syndrome, complaint of pain and poor quality of sleep in this population. The prevalence of ischemic and hemorrhagic strokes, as well as the classification of ischemic strokes was made according the TOAST criteria.
The Mann-Whitney test was used to compare good sleepers (PSQI < 5) and poor sleepers (PSQI > 5). Logistic regression analysis was applied considering the STOP-BANG score as an independent variable and sleep quality measured by the PSQI as the dependent variable, controlled for age and sex.
RESULTS
The mean age was 59.8 ± 12.9 years, 51.5% were male, the BMI was 26.5 ± 5.1 kg/m[2], with the interview done within 163 ± 141 days after stroke. We observed a low average NIHSS score (2.8 ± 2.1) and degree of disability as measured by the mRS (1.5 ± 1.1). The prevalence of hypertension, diabetes mellitus and smoking were 83.8%, 35.3% and 22.1%, respectively. Of the 68 patients, 50 (73.5%) complained of pain, only nine (13.2%) filled the diagnostic criteria for restless legs syndrome, and 48 (70.6%) had poor sleep quality ([Table 1]).
Table 1
Demographic data and characteristics.
|
Parameter
|
Sample (n = 68)
|
|
Age (years)
|
59.8 ± 12.9
|
|
Male
|
35 (51.5%)
|
|
Body-mass index (kg/m[2])
|
26.5 ± 5.1
|
|
Hypertension*
|
57 (83.8%)
|
|
Diabetes**
|
24 (35.3%)
|
|
Current smoker
|
15 (22.1%)
|
|
Restless legs syndrome
|
9 (13.2%)
|
|
Pain complaint
|
50 (73.5%)
|
|
NIHSS
|
2.8 ± 2.1
|
|
Mrs
|
1.5 (1.1)
|
|
STOP-BANG
|
4.3 ± 1.8
|
|
STOP-BANG ≥ 3
|
57 (83.8%)
|
|
PSQI
|
76 ± 3.9
|
|
Bad sleepers (PSQI ≥ 6)
|
48 (70.6%)
|
Data are mean (SD) or n (%).
*Defined as a systolic blood pressure of 140 mm Hg or higher or a diastolic blood pressure of 90 mm Hg or higher, or current use of antihypertensive medication;
**Defined as a fasting blood glucose concentration of 126 mg/dl or higher or current use of antidiabetic medication; NIHSS:National Institutes of Health Stroke Scale; mRS: Modified Rankin Scale; PSQI: Pittsburgh Sleep Quality Index.
Sixty-four (94.1%) patients had ischemic stroke and four (5.9%) had hemorrhagic stroke. The TOAST etiology classified the strokes as occlusion of small vessels (32.8%), inconclusive (26.6%), large artery atherosclerosis (18.8%), cardio- embolic (15.6%), and other causes (6.3%).
The STOP-BANG and PSQI scores were 4.3 ± 1.8 and 7.6 ± 3.9, respectively. Good sleepers (PSQI ≤ 5) were compared with poor sleepers (PSQI > 5). No significant differences were seen between good or poor sleepers for sex, presence of hypertension, diabetes mellitus, smoking, restless legs syndrome or the etiologic classification of stroke by TOAST. The STOP-BANG scores were higher in poor sleepers than good sleepers (4.5 ± 1.6 versus 3.5 ± 1.9; p = 0.032).
Logistic regression analysis was used to identify predictors of subjective sleep quality (PSQI score) making the STOP-BANG a predictor of a poor-quality sleep, at p < 0.05 and relative risk of 1.6, controlled for age and sex ([Table 2]).
Table 2
Logistic regression analysis considering the STOP-BANG scores as an independent variable and sleep quality measured by the Pittsburgh Sleep Quality Index as the dependent variable, controlled for age and sex.
|
Variables
|
Beta coefficient
|
RR
|
95%CI
|
p
|
|
STOP-BANG (each score)
|
0.478
|
1.61
|
1.03-2.51
|
0.035
|
|
Age (each year)
|
-0.023
|
0.98
|
0.93-1.02
|
0.340
|
|
Male sex
|
0.821
|
2.27
|
0.50-10.20
|
0.284
|
DISCUSSION
We found that the STOP-BANG score worked as a predictor of a poor quality of sleep with a relative risk of 1.6, reflecting the impact of nighttime breathing problems on the sleep quality of post-stroke patients.
Quality of sleep is an important issue in stroke patients. Complaints of insomnia and increased sleep latency have been identified as predictors of a poor quality of sleep in patients after stroke[2]. Interestingly, self-reported questionnaires were better as predictors of sleep quality than sleep studies in patients with obstructive sleep apnea[25].
The identification and treatment of predictors of poor sleep quality after stroke is very important, due to the potential impact on the patient's quality of life. According to the PSQI, 70.6% of our patients were considered poor sleepers (7.6 ± 3.9 points).
On the other hand, the sensitivity of the STOP-BANG questionnaire (three or more affirmative answers) for obstructive sleep apnea detection was 83.6%. This confirms that our patients had a higher risk of nocturnal breathing complaints after stroke. In fact, the higher scores of the STOP-BANG in poor sleepers (4.5 ± 1.6) compared with good sleepers (3.5 ± 1.9) indicate the large influence of nocturnal breathing problems on the quality of sleep after stroke in our cohort.
In contrast to the PSQI, the STOP-BANG is a practical tool: it is short, has an easy-to-remember mnemonic and a simple calculable scoring system. Furthermore, patients have relatively little difficulty in answering it, giving a high overall response rate[26]. The identification of impaired sleep quality and frequency of sleep disturbances in patients with stroke can lead to corrective measures, such as the establishment of proper routines and habits, as well as more appropriate time for therapeutic interventions[27],[28].
We are unaware of previous studies addressing the impact of nighttime respiratory problems measured by the STOP-BANG questionnaire in the sleep quality of patients after stroke. However, a few limitations must be highlighted. The characteristics of sleep analyzed were determined exclusively by self-reported data, without confirmation through complementary tests. In addition, we included both ischemic and hemorrhagic stroke patients, although they have different pathophysiological mechanisms[29].
This study indicates that sleep quality was greatly influenced by sleep-related breathing problems, which were well identified by the STOP-BANG questionnaire, especially in younger stroke patients.
