A Cross-sectional Study of the Occurrence and Effect of Obstructive Sleep Apnea in Subjects With Resistant Hypertension

The recruitment status of this study is unknown because the information has not been verified recently.
Verified July 2010 by The University of Hong Kong.
Recruitment status was  Recruiting
Information provided by:
The University of Hong Kong
ClinicalTrials.gov Identifier:
First received: February 12, 2009
Last updated: July 27, 2010
Last verified: July 2010

This study aims to investigate the prevalence of obstructive sleep apnea (OSA) in subjects with resistant hypertension and to evaluate the relationship between parameters of OSA severity and blood pressure control

Obstructive Sleep Apnea
Resistant Hypertension

Study Type: Observational
Study Design: Observational Model: Case-Only
Time Perspective: Cross-Sectional
Official Title: A Cross-sectional Study of the Occurrence and Effect of Obstructive Sleep Apnea in Subjects With Resistant Hypertension

Resource links provided by NLM:

Further study details as provided by The University of Hong Kong:

Biospecimen Retention:   Samples Without DNA

Blood test for glucose, lipid, vascular and metabolic markers

Estimated Enrollment: 96
Study Start Date: February 2009
Estimated Primary Completion Date: February 2011 (Final data collection date for primary outcome measure)
resistant hypertension subjects
subjects with resistant hypertension

Detailed Description:

Obstructive sleep apnea (OSA) is characterized by intermittent upper airway collapse during sleep, which results in hypoxia, arousals and surge in sympathetic activity. There is robust evidence to support a contributing role of OSA in hypertension (HT). The Sleep Heart Health Study (1), which recruited more than 6000 subjects having polysomnogram at home, found an independent association between OSA and HT. The adjusted odds ratio was 1.37 for subjects with and apnea-hypopnea index >= 30/hour compared to those without apnea. The Wisconsin Sleep Cohort Study , which provided prospective longitudinal follow-up for OSA subjects over 4 years, have shown dose dependency of the severity of OSA and the risk of development of HT. Current available data suggests that in hypertensive patients with severe OSA, there is a BP drop of about 10mmHg with CPAP treatment (2-5). The blood pressure (BP) lowering effect of CPAP treatment in the group with mild asymptomatic OSA is less consolidated.

The relationship between BP and risk of cardiovascular events is continuous, consistent, and independent of other risk factors. A strict blood pressure control is imperative in subjects with diabetes mellitus or renal impairment. Resistant hypertension is defined as blood pressure that remains above goal in spite of concurrent use of 3 antihypertensive agents of different classes. (6) Resistant hypertension is defined in order to identify patients who are at risk of having secondary causes of hypertension, and who may benefit from specific diagnostic and therapeutic applications. Despite the fact that OSA is listed as one of the causes of resistant HT (6), paucity of works has demonstrated the scale of problems of untreated OSA in subjects with resistant HT. (7-9) There is so far one study demonstrating the beneficial effect of CPAP treatment in subjects with resistant HT, though no randomization was implemented and the sample size was limited (n=11). (10) We aim at conducting a cross-sectional study to explore the situation which would guide further clinical trial.


Ages Eligible for Study:   18 Years to 65 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   No
Sampling Method:   Non-Probability Sample
Study Population

Consecutive sampling of subjects who attend Hypertension clinic , Department of Medicine, Queen Mary Hospital, and who fulfill the inclusion criteria.


Inclusion Criteria:

  • ≧ 3 anti-HT drugs
  • age 18-65
  • mentally fit for signing an informed written consent

Exclusion Criteria:

  • moderate renal impairment (glomerular filtration rate <30 mL/min/m2 )
  • endocrine/renal/cardiac causes of secondary HT
  • congestive heart failure and clinically fluid overloaded
  • On drugs that elevate BP e.g. alcohol, NSAID, steroid
  Contacts and Locations
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Please refer to this study by its ClinicalTrials.gov identifier: NCT00843583

Contact: Sau Man Mary Ip, MD 852-28554455 msmip@hkucc.hku.hk
Contact: Mei Sze Macy Lui, MRCP 852-28553312 macylui@graduate.hku.hk

Hong Kong
Department of Medicine, The University of Hong Kong, Queen Mary Hospital Recruiting
Hong Kong, Hong Kong, 852
Contact: Sau Man Mary Ip, MD    852-28554455    msmip@hkucc.hku.hk   
Sponsors and Collaborators
The University of Hong Kong
Principal Investigator: Sau Man Mary Ip, MD Department of Medicine, The University of Hong Kong
  More Information


Responsible Party: Professor Ip, Sau Man Mary, Department of Medicine, The University of Hong Kong, Queen Mary Hospital
ClinicalTrials.gov Identifier: NCT00843583     History of Changes
Other Study ID Numbers: NCT00808421
Study First Received: February 12, 2009
Last Updated: July 27, 2010
Health Authority: Hong Kong: Ethics Committee

Keywords provided by The University of Hong Kong:
obstructive sleep apnea
resistant hypertension

Additional relevant MeSH terms:
Sleep Apnea Syndromes
Sleep Apnea, Obstructive
Cardiovascular Diseases
Nervous System Diseases
Respiration Disorders
Respiratory Tract Diseases
Signs and Symptoms
Signs and Symptoms, Respiratory
Sleep Disorders
Sleep Disorders, Intrinsic
Vascular Diseases

ClinicalTrials.gov processed this record on October 20, 2014