Sleep Apnea: Epidemiology And Pathophysiology Harneet K Walia, MD, FAASM Center for Sleep Disorders Cleveland Clinic April 15, 2015

Objectives • Describe the Prevalence of Obstructive Sleep Apnea (OSA) • Discuss the Epidemiology of OSA • Discuss the Pathophysiology and Pathophysiological Consequences of OSA

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Obstructive Sleep Apnea Pathophysiology • Repetitive airway obstruction or collapse occurring during sleep • Associated with arousals and/or oxyhemoglobin desaturation • To break an apnea the brain briefly “wakes up” (sleep fragmentation) • During the apnea there is hypoxia, hypercapnia, and a rise in BP

Obstructive Sleep Apnea Syndrome • When OSA is associated with daytime symptoms, such as excessive daytime sleepiness • AHI ≥ 5 with symptoms or AHI ≥ 15 • Apnea Hypopnea Index (AHI) - Number of apneas plus hypopneas per hr of sleep • AHI ≥ 5 = mild OSA • AHI ≥ 15 = moderate OSA • AHI ≥ 30 = severe OSA

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Obstructive Apneas

Hypopneas

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Pathophysiology of OSA

Pathophysiology • Upper airway Collapsibility • Effects of Lung Volumes-loss of caudal traction • Upper Airway Dilator Muscle ActivityGenioglossus • Arousal response in OSA • Upper airway anatomy-lateral wall thickness, tongue volume, small maxilla and small mandible • Fluid shifts Chebbo, Sleep Medicine Clinics, 2013 Redolfi S, AMJRCCM, 2009

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Sleep Apnea Pathophysiology

Schwab et.al. Am J Respir Crit Care Med, 1995

Pathophysiological Effects of OSA

Sleep

Decrease Airway Tone

Apnea Hypoxia

Re-oxygenation

Ventilation

Re-establish Airway Tone

Pleural pressure swings

Arousal Sympathetic activation

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Epidemiology of sleep Apnea

Population-based OSA and OSAS prevalence studies Study

# subjects

AHI ≥ 5 AHI ≥ 15 OSAS

Methods

WI, 1993

M=352 W=250 (age 30-60)

M=24% W=9%

M=9% W=4%

M=4% W=2%

PSG

PA, 1998, 2001

M=741 W=1000 (age 20-100)

M=17% W=5%

M=7% W=2%

M=3.3% W=1.2%

PSG

Spain, 2001

M=325 W=235 (age 30-70)

M=26% W=28%

M=14% W=7%

M=3.4% W=3%

PSG

Australia, 1995

M=294 (age 40-65)

M=25.9%

M=10% (AHI>=10)

M=3.1% W=n/a

HST

Hong Kong, 2001, 2004

M=153 W=106 (age 30-60)

M=8.8% W=3.7%

M=5.3% W=1.2%

M=4.1% W=2.1%

PSG

Korea, 2004

M=309, W=148 (age 40-69)

M=27% W=16%

M=10.1% W=4.7%

M=4.5% W=3.2%

PSG or HST

India, 2006

M=88 W=63 (age 30-60)

M=19.7% W=7.4%

n/a

M=4.9% W=2.1%

PSG

Adapted from Lee et al. Expert Rev Respir Med 2008;2:349-364

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Increased prevalence of Sleep Disordered Breathing • • • • •

Moderate to severe SDB (AHI ≥15) 10% among 30–49-year-old men 17% among 50–70-year-old men 3% among 30–49-year-old women 9% among 50–70 year-old women Relative increases of between 14% and 55% depending on the subgroup in the last 2 decades Peppart et al, Amer Jour of Epid, 2013, April 14

Risk Factors Modifiable

Non-Modifiable

• Obesity • Medications - opiates - benzodiazepines - alcohol • Smoking • Nasal congestion

• Gender • Genetic predisposition • Race • Aging • Menopause • Craniofacial anatomy Young et al. JAMA 2004;291:2013-2016

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Ethnicity • Similar prevalence in Asian populations when compared to Western societies - Despite lower BMI in Asians - Could be attributed to cephalometric differences • Limited data on prevalence of OSA in Hispanics-however higher odds than whites Ip et al. Chest 2001;119:62-69 Ip et al. Am J Respir Crit Care Med 2001;163:A636 Ip et al. Chest 2004;125:127-134 O’Connor et al. Sleep 2003;26:74-79 Chen et al. Sleep 2014 Nov 20

Ethnicity • Population based studies suggest that OSA prevalence is as high or higher in African Americans (AA) compared with Caucasians • For community dwelling AA >65 years, odds of severe OSA was 2.5 x greater relative to Caucasians • AA had 2 times higher odds of mild OSA than whites

Ancoli-Israel et al. Am J Respir Crit Care Med 1995;1946-1949 Chen et al. Sleep 2014 Nov 20

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Ethnicity • Cleveland Family Study: - OSA prevalence is higher in AA 65 years • Prevalence for moderate OSA (AHI ≥15) varies from 7- 44%

Duran, et al. Am J Respir Crit Care Med 2001;163:685-689 Bixler, et al. Am J Respir Crit Care Med 1998;157:144-148 Bixler, et al. Am J Respir Crit Care Med 2001;163:608-613

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Aging • For ages 65-95 years - HST – 427 people - OSA defined as an AHI >10 occurred in 70% of men and 56% of women • 3x higher than middle age prevalence estimates

• For ages 71-100 years - Spain cohort - AHI > 5: 81% men and 80% women • 3x higher than middle age

- AHI > 15: 57% men and 49% women • 4x higher than middle age Ancoli-Israel et al. Sleep 1991;14:486-495 Durán, et al. World Conference Space Odyssey, 2001

Aging • MrOs Sleep Study - AHI > 15, prevalence estimate of 21.4%-26.4% - Prevalence increased with increasing age • 22.8% < 72 years • 30.1% > 80 years

• Cleveland Family Study - Higher prevalence for AHI > 15 if >60 years compared with 25-60 years - Men: 42% vs. 22%; Women: 32% vs. 4%

• Sleep Heart Health Study - AHI > 15, 1.7 fold higher proportion in older (60-99 years) vs. younger (40-60 years) Mehra, et al. JAGS 2007;55:1356-1364 Redline, Semin Respir Crit Care Med 1995 Young et al. Arch Intrn Med, 2002

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Sleep Heart Health Study Prevalence by Age

Young AJRCCM 2002

Obesity

• Alterations in: - Upper Airway Structure • Altered geometry

- Function • Increased collapsibility

- Respiratory Drive - Load Compensation • ↓ FRC and ↑ oxygen demands

10% weight gain predicts ~30% increase in AHI 10% weight loss predicts ~30% reduction in AHI If AHI65 yrs Sex: M>W Heart Failure Stroke Medical Conditions Opiod Use Renal Failure Afib Acromegaly

Bixler, AMJRCC, 1998, 2001 Bradley, Circulation, 2003 Bassetti, Sleep, 1999 Wang, Chest, 2005

Conclusion • OSA is characterized by repeated episodes of complete or partial obstruction of the upper airway during sleep • Understanding of pathophysiology of sleep apnea is evolving-is under diagnosed condition • Pathophysiological changes of sleep apnea can have various adverse consequences

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