Stroke

The prevalence of stroke in US adults in 2005 was 6.5 million; for 2009, associated costs were estimated at $70 billion.1 Numerous studies have shown that patients suffering from sleep apnea have an increased risk of stroke.

  • Sleep apnea is a risk factor for stroke independent of other cardiovascular and cerebrovascular risk factors. Increased risk of stroke is observed even in cases of mild sleep apnea (AHI less than 10 events/hr).2
  • The prevalence of sleep apnea in stroke patients has been shown in several studies to be greater than 60%.3,4,5
  • Multivariate analysis of 152 patients with acute ischemic stroke indicated that age, a history of diabetes, and night time onset of stroke were independent predictors of AHI.6
  • Survival rates of stroke patients who have untreated sleep apnea are markedly worse than patients without sleep apnea.7
  • Minoguchi et al. demonstrated that the prevalence of silent brain infarction (SBI) is increased in patients with sleep apnea compared with obese controls.8 The presence of SBI is an independent predictor of increased stroke risk in older individuals.9
  • The Minoguchi study also demonstrated elevated serum levels of soluble CD40 ligand and soluble P-selectin in patients with moderate to severe sleep apnea. These proteins have been shown to be markers of platelet activation and future cardiovascular and cerebrovascular events.10,11

Physiological Mechanisms Linking Sleep Apnea and Stroke

The recurring intermittent hypoxia associated with sleep apnea may contribute to systemic inflammation and platelet activation and subsequently lead to SBI.12 Sleep apnea has been shown to increase the levels of various inflammatory markers, including C-reactive protein, interleukin 6, and tumor necrosis factor alpha.13,14

Sleep apnea-induced hypertension is another factor that may contribute to an increased risk of stroke. Untreated sleep apnea is strongly associated with hypertension, and is listed as an identifiable cause of hypertension in the National Institute of Health’s seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure.

Effects of Treatment

Studies have shown that treatment of sleep apnea may reduce the risk of stroke.

  • Effective treatment of sleep apnea with continuous positive airway pressure (CPAP) has been shown to lead to a significant reduction in diurnal and nocturnal blood pressure, which is the main risk factor for stroke.15
  • CPAP treatment of sleep apnea has been shown to reduce the risk of new vascular events in stroke patients.16
  • Serum levels of soluble CD40 ligand, soluble P-selectin, and C-reactive protein, markers of elevated risk of future stroke, were decreased after 3 months of CPAP therapy for sleep apnea.17,18

1 American Heart Association. Heart Disease and Stroke Statistics—2009 Update
2 Shahar E et al. Am J Respir Crit Care Med 2001;163:19-25
3 Dyken ME et al. Stroke 1996;27:401-7
4 Bassetti C et al. Neurology 1996;47:1167-73
5 Parra O et al. Am J Respir Crit Care Med 2000;161:375-80
6 Bassetti CL et al. Stroke 2006;37:967-72
7 Sahlin C et al. Arch Intern Med 2008;168:297-301
8 Minoguchi K et al. Am J Respir Crit Care Med 2007;175:612-7
9 Bernick C et al. Neurology 2001;57:1222-29
10 Ridker PM et al. Circulation 2001;103:491-5
11 Novo S et al. Stroke 2005;36:673-5
12 Minoguchi K et al. Am J Respir Crit Care Med 2007;175:612-7
13 Yokoe T et al. Circulation 2003;107:1129-34
14 Minoguchi K et al. Chest 2004;126:1473-79
15 Becker HF et al. Circulation 2003;107:68-73
16 Martinez-Garcia MA et al. Chest 2005;128 :2123-9
17 Minoguchi K et al. Am J Respir Crit Care Med 2007;175:612-7
18 Yokoe T et al. Circulation 2003;107:1129-34