Prospective cohort study on the effect of surgical treatment of obstructive sleep apnea syndrome on blood pressure (and other cardiovascular risk factors).

Obstructive sleep apnea syndrome (OSAS) is the most common sleep disorder and
increasingly recognised as a major health problem. The prevalence of OSAS in
the middle aged population is 2% of women and 4% of men. (1) In the Netherlands
40,000 men and 20,000 women suffer from OSAS. (2) It*s estimated that 80% of
OSAS patients remains undiagnosed (3).
OSAS is defined by the American Academy of Sleep Medicine Task Force (1999) as
more than five obstructive apneas or hypopneas per hour of sleep and excessive
daytime sleepiness, not explained by other factors, or two or more of the
following symptoms: gasp for breath during sleep, repeated nocturnal awakening,
non recuperative sleep, diurnal fatigue and altered concentration. (4) The
severity of OSAS is expressed in the apnea hypopnea index (AHI). An AHI of 5-15
is mild OSAS, an AHI of 15-30 is moderate and AHI >30 is severe OSAS, as
assessed by polysomnography. (5)
The chief pathophysiological event is abnormal narrowing of the upper airway
during sleep and loss of tone in the pharyngeal muscles. OSAS is being treated
because of its complaints, but also since it is becoming increasingly clear
that OSAS is associated with considerable comorbidity, including hypertension
and increased risk for other cardiovascular diseases. Nocturnal and daytime
blood pressure are raised in patients with OSAS. This effect is independent of
obesity and other risk factors for raised blood pressure (6-10).
Treatment of OSAS consists of lifestyle alterations, as weight reduction in
case of overweight, and abstinence of alcohol, sedatives and sleep medication.
Non-invasive treatment consists of the use of a mandibular repositioning
appliance (MRA) in mild to moderate OSAS. The *golden standard* treatment of
moderate to severe OSAS is nasal continuous positive airway pressure (nCPAP).
NCPAP acts as *pneumatic splint*, keeping the upper airway open during sleep.
A randomised parallel trial in which therapeutic and sub-therapeutic nCPAP in
men with OSAS were compared showed that therapeutic nCPAP reduced mean arterial
ambulatory blood pressure by 2.5 mm Hg. In patients with most severe sleep
apnea, nCPAP reduces blood pressure providing significant vascular risk
benefits. (11) Unfortunately, 40% of OSAS patients can*t tolerate nCPAP therapy
for a variety of reasons.
Surgical treatment for OSAS aims to relieve the obstruction. The principal
interventions are:
1) Nose and sinus surgery to increase nasal passage, in case of decreased nasal
passage;
2) If the obstruction is on palate-uvula-tonsil level, therapeutic options
consist of radiofrequent ther-motherapy, laser-assisted uvuloplasty,
uvulopalatopharyngoplasty (UPPP), with or without tonsillectomy;
3) while in retrolingual obstruction surgical options are radiofrequency of the
tongue base or hyoid sus-pension. In case of severe OSAS and multilevel
obstruction, multilevel surgery in one tempo is increasingly performed. (2)
So far no studies have been performed assessing the effect of successful
surgical treatment of OSAS on blood pressure and other cardiovascular
parameters in patients with moderate to severe OSAS.

1. Young T, et al. The occurrence of sleep-disordered breathing among
middle-aged adults. N Engl J Med. 1993 Apr 29;328(17):1230-5
2. de Vries N, Boudewyns A. Slaapgebonden ademhalingsstoornissen.
In:
Leerboek Keel-, neus en oorheelkunde. Huizing EH, van de Heyning P,
Graamans K, Snow GB, de Vries, N (eds). Bohn Stafleu van Loghem ,2007,
in
press
3. Banno K, et al. Increasing obesity trends in patients with sleep-disordered
breathing referred to a sleep disorders center. J Clin Sleep Med
2005;1:364-6
4. Sleep-related breathing disorders in adults: recommendations for syndrome
definition and measurement techniques in clinical research. The Report
of an
American Academy of Sleep Medicine Task Force. Sleep. 1999 Aug
1;22(5):667-89
5. Young T, et al. Epidemiology of obstructive sleep apnea: a population health
perspective. Am J Respir Crit Care Med. 2002 May 1;165(9):1217-39
6. Marin JM,et al. Long-term cardiovascular outcomes in men with obstructive
sleep apnea-hypopnea with or without treatment with continuous
positive
airway pressure: an observational study. Lancet 2005;365:1046-53
7. Shamsuzzaman ASM, et al. Obstructive sleep apnea, implications for cardiac
and vascular disease, JAMA 2003;290:1906-14
8. Nieto FJ, et al. Association of sleep-disordered breathing, sleep apnea, and
hypertension in a large community-based study. Sleep Heart Health
Study.
JAMA. 2000 Apr 12;283(14):1829-36
9. Peppard PE, et al. Prospective study of the association between
sleep-disordered breathing and hypertension. N Engl J Med. 2000 May
11;342(19):1378-84
10. Davies CWH, et al. Case control study of 24-hour ambulatory blood
pressure
in patients with obstructive sleep sleep apnoea and normal matched
control
subjects. Thorax 2000;55:736-40
11. Pepperell JC, et al. Ambulatory blood pressure after therapeutic and
subtherapeutic nasal continuous positive airway pressure for
obstructive
sleep apnea:a randomised parallel trial.Lancet 2002;359:204-10

In The Netherlands 2% of women and 4% of men suffer from Obstructive Sleep
Apnea Syndrome (OSAS). NCPAP, the gold standard therapy for moderate to severe
OSAS has been shown to reduce blood pressure in OSAS. NCPAP therapy is however
hampered by compliance issues; 40% of patients will not use it in the long run,
others use it for only a few hours/night and/or not 7days/week. Results of
surgery for OSAS are improving. The effects of surgery on cardiovascular
parameters have not yet been studied. If surgery leads to a sufficient lowering
of the AHI, the effect is present 7 nights per week. We want to study blood
pressure, lipids spectrum and fasting glucose level preoperative and 3 and 6
months postoperative in patients with moderate to severe OSAS who undergo
surgery. In this way we will be able to evaluate the effect of successful OSAS
surgery on cardiovascular risk.

Prospective cohort study.

OSAS surgery; the principal interventions are:
1) Nose and sinus surgery to increase nasal passage, in case of decreased nasal
passage;
2) If the obstruction is on palate-uvula-tonsil level, therapeutic options
consist of radiofrequent ther-motherapy, laser-assisted uvuloplasty,
uvulopalatopharyngoplasty (UPPP), with or without tonsillectomy;
3) while in retrolingual obstruction surgical options are radiofrequency of the
tongue base or hyoid sus-pension. In case of severe OSAS and multilevel
obstruction, multilevel surgery in one tempo is increasingly performed.

Patients will visit the ENT department of the St Lucas Andreas hospital at
least 3 times within the 6 month follow up. Blood will be drawn, an ECG will be
performed and 24 hour blood pressure will be recorded 3 times within the 6
month follow up (0, 3 and 6 months).
Physical and psychological discomfort associated with above mentioned
investigations include: painful elbow because of the venapuncture and exercise
limitation because of the 24 hour blood pressure monitoring.
As far as we know, these investigations aren't of any risk to the patient.