Daytime sleepiness more severe in normotensive patients with moderate-to-severe OSA
Patients with moderate-to-severe obstructive sleep apnoea (OSA) who do not have hypertension have higher levels of daytime sleepiness than those with hypertension, as evidenced in a recent study.
“[S]ubjective daytime sleepiness among normotensive subjects was significantly more severe than that in hypertensive subjects with moderate-to-severe OSA,” said the researchers.
Study participants were 280 adults (mean age 51.7 years, 27.1 percent female) enrolled in a sleep study in a single centre in Hong Kong. About 62 percent of patients were identified as having moderate-to-severe OSA, as determined by an Apnea-Hypopnea Index (AHI) score of ≥15/hour. A total of 136 patients (48.6 percent) had hypertension. Daytime sleepiness was measured using the Epworth Sleepiness Scale (ESS).
Mean ESS score was significantly higher among normotensive than hypertensive patients (11.3 vs 9.4; p=0.003), as well as among those without than with cerebrovascular disease (10.5 vs 6.3; p=0.048). [J Clin Hypertens (Greenwich) 2019;doi:10.1111/jch.13485]
The association was less clear when comparing AHI scores of the patients, with a nonsignificant higher mean ESS score among those with AHI <15/hour (mild OSA) compared with ≥15/hour (10.8 vs 9.6; p=0.075).
Patients with moderate-to-severe OSA who were normotensive had higher adjusted mean ESS score compared with patients with mild OSA who were normotensive (13.11 vs 9.35), those with mild OSA who were hypertensive (9.70), and those with moderate-to-severe OSA who were hypertensive (9.43).
When AHI cut-off values were increased to <30/hour and ≥30/hour, normotensive patients with AHI ≥30/hour still had higher mean ESS score compared with normotensive patients with AHI <30/hour (13.4 vs 10.6), hypertensive patients with AHI <30/hour (9.9), and hypertensive patients with AHI ≥30/hour (8.6).
Questions remain regarding the mechanism behind the association between hypertension, daytime sleepiness, and OSA, said the researchers, recommending future studies look into this area.
“[One study] reported that patients with excessive daytime sleepiness, when compared with those without, had significantly lower baroreflex sensitivity and significantly higher low‐to‐high frequency power ratio of heart rate variability during the different stages of nocturnal sleep [while another suggested that] daytime sleepiness could be an effect modifier of the association between sleep‐disordered breathing with hypertension,” said the researchers. [J Sleep Res 2008;17:263-270; Sleep 2008;31:1127-1132]
One study also suggested using ESS to help identify patients with OSA who have an elevated risk of hypertension. [Sleep Breath 2012;16:31-40]
Another potential avenue for research is the role of continuous positive airway pressure (CPAP) in lowering blood pressure among patients with OSA. Previous studies on the effect of CPAP have produced conflicting results, said the researchers, with some studies showing no difference in blood pressure following CPAP in patients with OSA and hypertension [Eur Respir J 2006;27:1229-1235] and others showing a benefit only following >4 hours of use. [Thorax 2014;69:1128-1135]