A Clinical Study On The Association Of Sleep Apnea Syndrome And Hypertension

Objective:Obstructive sleep apnea syndrome（OSA）is associated with hypertension.The role of OSA in hypertension and the factors involving effect of OSA treatment on blood pressure are still unclear.The aim of the study was to investigate the relationship between ambulatory blood pressure and nocturnal intermittent hypoxia,examine the effect of continuous positive airway pressure（CPAP）treatment on night-time blood pressure in patients with nocturnal hypertension,and evaluate the night-time blood pressure lowering efficacy and tolerability of initial high（5.0 mg/day）versus low（2.5 mg/day）dose of S-（-）-amlodipine in mild and moderate hypertension.Methods:（1）2349 subjects from Outpatient Clinic underwent ambulatory blood pressure monitoring（ABPM）and nocturnal pulse oximetry on the same day.For analysis,study participants were divided into four groups according to their oxygen desaturation index（ODI）values（ODI<5,5-14,15-29,≥30 events/h）.（2）Sixty patients with nocturnal hypertension and OSA were randomized to either CPAP treatment or sham-CPAP（sub-therapeutic CPAP,about 4 cm H₂O pressure）for 3 months.ABPMs were performed at the initial and terminating visits for all subjects.The primary end point was the change in night-time mean systolic/diastolic blood pressure after 3 months of follow-up.（3）A total of 701 patients from 22 centers were randomly allocated 8-week treatment of S-（-）-amlodipine 2.5 mg/day or 5.0 mg/day,respectively.In the present analysis,patients（n=523）who had valid ambulatory blood pressure recordings both at baseline and at 8 weeks of follow-up were included.Results:（1）With increasing ODI,night-time,24-h,daytime and night-time systolic/diastolic blood pressures significantly increased（P for trend<0.01）,especially night-time（ODI<5 events/h,113.9/72.4 mm Hg;ODI 5-14 events/h,115.1/72.8 mm Hg;ODI5-14 events/h,118.9/76.2 mm Hg;ODI≥30 events/h,127.6/81.5 mm Hg,P for trend<0.0001）.24-h,daytime and night-time pulse rate also significantly increased with ODI（P for trend<0.01）.（2）After 3 months of treatment,night-time systolic/diastolic blood pressure（±standard error）in the CPAP group（n=26）decreased by 1.3±2.4/1.4±1.7 mm Hg.The corresponding changes in the sham-CPAP group（n=21）were1.1±2.2/-0.4±1.5 mm Hg,respectively.The between-group differences in the changes in night-time systolic and diastolic blood pressure were 0.3（95%confidence interval-6.4 to 7.0,P=0.93）and 1.7（-2.9 to 6.3,P=0.46）mm Hg,respectively,in favor of CPAP.（3）After 8 weeks of treatment,night-time systolic/diastolic blood pressure（±standard error）in the S-（-）-amlodipine 2.5 mg group（n=263）decreased by4.9±0.8/3.3±0.6 mm Hg.The corresponding changes in the S-（-）-amlodipine 5 mg group（n=260）were 8.3±0.9/4.7±0.6 mm Hg,respectively.The between-group differences in the changes in night-time systolic and diastolic blood pressure were3.4（95%confidence interval 1.1 to 5.7,P=0.004）mm Hg and 1.4（-0.3 to 3.0,P=0.07）mm Hg,respectively,in favor of the high initial dose of amlodipine.The incidence rate was not significantly（P≥0.50）different for all adverse events（17.7%vs.20.0%）.Conclusions:Ambulatory blood pressure and pulse rate were positively associated with ODI,indicating a possible role of sympathetic activation in the pathogenesis of hypertension in sleep apnea.In patients with nocturnal hypertension and OSA,3 months of CPAP treatment did not significantly influence blood pressure.Initial high-dose of S-（-）-amlodipine,however,significantly improved night-time blood pressure control with similar tolerability as the initial low dose in mild or moderate hypertension.