The study revealed that the prevalence of snoring among hypertensive Nigerians in this study was 50%. It also revealed that almost all the hypertensive snorers reported excessive daytime somnolence as predicted using the Epworth sleepiness scale. Male hypertensive subjects had a significantly higher frequency of snoring than their female counterparts. In men the frequency of snoring was 55% while it was 46.7% among female participants in the study. This is similar to what has been reported among other hypertensive population [14
]. The prevalence of snoring among these hypertensive subjects was however greater than that reported among non-hypertensive Nigerians [11
]. Also, about 52% of hypertensive subjects were found to be at high risk for having obstructive sleep apnoea in this study. Hypertension is a well documented risk for developing sleep related difficulties such as sleep apnoea, hypopnoea and snoring [2
Individuals with OSA have been shown to have heightened sympathetic activity due to activation of chemoreceptors leading to peripheral vasoconstriction [15
]. OSA also results in the production of important neurohumoral mediators of cardiac and vascular disease [16
]. Individuals with OSA have increased production of the potent vasoconstrictor endothelin and impaired endothelial function, which affect vasomotion. OSA has also been associated with systemic inflammation, reflected by increases in C-reactive protein and serum amyloid A levels, which may advance atherosclerosis and is associated with increased cardiovascular risk. Perhaps through its effects on sympathetic activity or because of sleep deprivation, OSA may increase insulin resistance, which promotes cardiovascular risk via multiple pathways [17
]. Also, OSA is associated with increased levels of leptin, a hormone secreted by fat cells that is also associated with cardiovascular events.
This study also revealed that hypertensive subjects with positive history of snoring were significantly older than those without history of snoring. Furthermore, body mass index and fasting blood sugar were significantly higher among hypertensive subjects with history of snoring than those without it. This highlights the fact that hypertensive subjects with OSA likely have increased cardiovascular risk. The prevalence of snoring increased with increasing age group with the highest incidence among those in the sixth decade and the very elderly group (>70 years).This agrees with other studies have shown that obstructive sleep apnoea and snoring are directly related to age. With advancing age, sleep-related difficulties become increasingly common and often manifest as subjective complaints of difficulty falling asleep, reduced duration of night-time awakenings, and the amount of night-time sleep obtained [18
]. Mechanisms proposed for the age-related increase inprevalence include increased deposition of fat in the parapharyngeal area, lengthening of the softpalate, and changes in body structures surrounding the pharynx [20
Several epidemiologic studies have described the higher incidence of snoring and sleep apnoea among men compared to their female counterparts. Several explanation account for this: first, women may be less likely to report classical symptoms such as loud snoring, apnoea, nocturnal sorting or gasping [22
]. Secondly, differential response of the bed partner to the symptoms of obstructive breathing during sleep may also contribute to the clinical underrecognition of the disorder in women.
This study shows that hypertensive who were overweight or obese were more likely to be having sleep related disorders including snoring than those with normal body mass index. Similarly, a higher percentage of overweight and obese subjects were found to be at a high risk of obstructive sleep apnoea using the Berlin questionnaire. Epidemiologic studies from around the world have consistently shown body weight as the strongest risk factor for obstructive sleep apnea. In the Wisconsin Sleep Cohort study, a one standard deviation difference in body mass index (BMI) was associated with a 4-fold increase in disease prevalence [24
]. Other population- and community-based studies conducted in the United States and other countries have confirmed that excess body weight is uniformly associated with a graded increase in prevalence of obstructive sleep apnea [25