Epidemiological and Clinical Profile of Hypertensive Patients with Obstructive Sleep Apnea at CHU-B ()
1. Introduction
Obstructive sleep apnea syndrome (OSAS) is a common disease that affects middle aged adults and elderly adults. It is characterized by episodes of complete collapse of the airway or partial collapse with an associated decrease in oxygen saturation or arousal from sleep [1] . Other symptoms are daytime drowsiness, cognitive impairment, loud snoring. Obstructive sleep apnea (OSA) has significant implications in decreasing quality of life; driving safety and development of cardiovascular disease. In fact cohort studies have shown that in apneic untreated patients the risk of stroke is three time higher. That risk is multiplied by three for development of hypertension [2] . Traditionally polysomnography (PSG) in a sleep laboratory has been used as a reference standard for the diagnosis of OSA. PSG measures several sleep variables, one of which is the apnea-hypopnea index (AHI) or respiratory disturbance index (RDI). Generally an AHI of more than five events per hour of sleep is considered abnormal and the patient is considered to have a sleep disorder. An abnormal AHI accompanied by excessive daytime sleepiness is the hallmark for OSA diagnosis. Thus because of the lack of sleep laboratory in Africa and particularly in Congo, OSA is still underdiagnosed and a little described. However in this context the diagnosis is based on the presence of a light number of established criteria such as the Epworth questionnaire and the Berlin questionnaire [3] [4] . In Congo, this is a first study among hypertensive patients despite the absence of sleep laboratories.
2. Patients and Method
A descriptive and analytical prospective study was carried out in the cardiology and internal medicine department (outpatient consultations) of the University Hospital Center of Brazzaville (CHU-B), from March 2019 to August 2019 (6 months).
Were included to this study patients which were managed for hypertension. Informed consent was taken from each participant.
The sample size was estimated using Schwartz equation:
N = t2 × p × (1 − p)/m2
N: sample size, t: level of confidence (the value of a confidence level of 95% is 1.96), p: expected prevalence, m: precision (5%).
The expected prevalence was based on Konin et al. study [5] on presumption of obstructive sleep apnea among a population of black African hypertensive patients at Abidjan heart Institute. The calculated sample size was 380 people.
Demographic variables such as gender, age, marital status, educational level; medical history; clinical examination and antihypertensive drugs were documented in a survey sheet. The survey sheet was translated in different local languages to facilitate the filling of the informations.
The Berlin questionnaire was used to identify patients with obstructive sleep apnea. It has been documented to be clinically sensitive and correlates significantly with the presence of OSA among various populations. The questionnaire consists of 3 categories related to the risk of having sleep apnea. Patients can be classified into High Risk or Low Risk based on their responses to the individual items and their overall scores in the symptom categories (Appendix).
3. Conduct of the Study and Statistical Analysis
Patients meeting the inclusion criteria, after giving their written informed consent, filled the survey sheet and answered to the Berlin questionnaire. A clinical examination with measurement of the anthropomorphic parameters (weight, height, BMI, abdominal perimeter) and patients blood pressure was carried out. The data were processed by Epi info fR (CDC Atlanta USA). For the comparison of the percentages, the KHI square test was used. The Student t test was used for the averages. A calculation of the odds ratio (OR) and their confidence interval (CI) was made to look for the factors associated with the SAOS. For comparisons, the significance thresholds were p < 0.05.
4. Results
Epidemiological data
A total of 315 patients were included in the study. Women accounted for 66 per cent of cases, and the sex ratio was 1.6 in favor of women. The medium age of the patients was of 59 ± 13.3 years (extremes: 25 - 88 years) more than the half of the studied population was less than 60 years old.
Table 1 shows the repartition according to socio-demographics characteristics and gender.
In our sample, the majority of individuals were employed. Regarding the standard of living, we had 63.8% for the average standard of living; 19% for elevated living standards; 17.1 per cent for the low standard of living. 76 (31.8%) patients had been hypertensive for more than ten years.
Medical history and lifestyle habits of the studies population are resumed in Table 2.
We found a familiar history of high blood pressure in 215 (68.3%) patients, snoring in 200 patients (63.5%), diabetes in 116 (36.8%) patients. Associated cardiovascular risk factors were sedentary (57.7%), alcohol consumption (36%), diabetes (31%), known dyslipidemia (18.4%) and active smoking (2.1%). The anomalies of the Berlin questionnaire were: snoring (n = 197; 62.5%), waking fatigue (n = 127; 40.3%), fatigue during the day (n = 97; 30.8%), asleep at the wheel (n = 22; 27.5%).
In the univariate analysis, the factors associated with SAOS were: occupation OR (2.56) IC 95% (1.15 - 5.69), obesity by weight OR7.50 (1.60 - 35.1) and abdominal obesity OR 2.36 IC 95 % (1.36 - 4.08) (Table 3).
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Table 1. Socio-demographic characteristics by gender.
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Table 2. Distribution according to patient medical history and lifestyle habits.
5. Discussion
5.1. Prevalency
A correlation between obstructive sleep apnea syndrome and high blood pressure has been found in the literature. In our study, 239 patients were highly suspicious of SAOS, a prevalence of 75.8%. These results are consistent with those of S. Duong Qyu et al. 84%, Patri G et al. 35% - 83%, Logan AG et al. 75%. In Côte d’Ivoire, Morocco and the West, however, frequencies are lower, respectively 45%, 13.2% and 30%. This difference in frequency could be explained by sample size and type of patient recruitment.
5.2. Epidemiological Aspects
The average age of our series was 59 years old, more than half were under 60 years old, which is similar to Meslier et al. [6] , who found that the percentage of subjects with a high probability of OSA increased with age and increased three time between 33 and 64 years old. In the same idea order the study accomplished by of G. Cadelis and al [7] highlighted a statistically significant difference between subjects at high risk and at weak risk of developing OSA concerning the age. There was an increase in the risk of Obstructive Sleep Apnea Syndrome for patients older than 51 years. In Onen CH et al. [4] as well as in Konin C et al. [5] studies, age was not a significant factor in the occurrence of SAOS. Because age is a risk factor independently of presence of OSAS, these differences demonstrate that OSAS and HT are pathologies of adults. Our study found an OSAS greater frequency in women (64.9%). The predominance of the gender varies according to the series: women in Abidjan [5] , men in Vietnam [8] and in France [9] . The absence of a link between sex and OSAS during HT seems to confirm that it is a pathology that affects both women and men. In our study as in others [7] [10] the majority of individuals were employed. However, C. Konin et al. [5] found no significant link between the profession and the occurrence of the OSAS. Alcoholism was significant in the occurrence of OSAS in our study. In the literature it is clearly established that taking alcohol aggravates the symptoms of severe OSAS. M.F Scalan et al. report an increase in night events, including the number and duration of apnea and hypopnea when alcohol is taken in the evening before bedtime [11] . Although many studies [3] [12] show that smoking is a determinant of OSAS, we have not found a link between OSA and smoking. This is due to the low consumption of tobacco by patients in our sample, but also to the limited size of our sample.
5.3. Clinical Aspect
The presence of abdominal obesity was significant. These results are similar with the literature. Young T et al. [13] in 2002 showed that the risk of moderate to severe OSAS was independently associated with the abdominal perimeter. The main symptom of OSAS found in our study was snoring; in more than half of the cases. Other studies have reported this prevalence [6] [8] [14] [15] . The majority of apneic patients in our sample (60%) had antihypertensive multi-therapy. These results are identical to those of C. Konin et al. [5] Cote d’Ivoire, which reported 82.3%. This explains the resistance of HTA in OSAS [16] [17] and the fact that HTA in OSAS is difficult to control pharmacologically [18] . In our study the strong suspicion of OSAS was significantly associated with snoring p < 0.001), daytime drowsiness (wake fatigue p < 0.001; fatigue in the day p < 0.001).
These results support the criteria of the Berlin questionnaire. This confirms the interest of exploring sleep with polysomnography or ventilatory polygraphy in any patient complaining of snoring, excessive daytime fatigue, excessive daytime drowsiness
In the mixed analysis, the factors associated with (OSAS) were: occupation OR (2.56) 95% CI (1.15 - 5.69), obesity weight OR 7.50 (1.60 - 35.1) and abdominal OR 2.36 CI 95% (1.36 - 4.08)
5.4. Study Limit
The absence of polysomnography was a limitation of our study. So we used the Berlin questionnaire. To minimize the bias linked to the use of a questionnaire, it was translated into local languages and only one interviewer conducted the study.
6. Conclusion
The prevalence of obstructive sleep apnea syndrome is high during high blood pressure in our context. Hence the need to explore sleep through polysomnography, and the prevention that goes through the fight associated risk factors.
Appendix