1. The Relationship of Weight
and
Obstructive Sleep Apnea
Mia Zaharna, MD, MPH
Stanford Sleep Center, Fellow
2. Objectives
• Background
• Discuss Obesity as a risk factor for OSA
• Discuss relationship of Obesity and OSA to health
effects
• Discuss Obesity as a consequence of OSA
• Discuss Treatment of OSA and its effect on
weight and vice versa
• Discuss ways that you can effectively control your
weight
Mia Zaharna - The Relationship of Weight and Obstructive SSlleeeepp AAppnneeaa
3. Background
• Obesity is the most powerful risk factor for obstructive
sleep apnea (OSA)
• Obesity is essentially the only reversible risk factor
• Potentially modifiable risk factors for OSA also include
alcohol, smoking, nasal congestion, and estrogen
depletion in menopause.
• Data suggest that obstructive sleep apnea is associated
with all these factors, but at present the only
intervention strategy supported with adequate
evidence is weight loss. ( Young et al. 2002)
5. Background: OSA Prevalence
• OSA present in 25-58% of men and 10-37% of women
(Young et al 1993), (Young et al 2002)
• Prevalence increases in middle age
• Symptomatic OSA (OSA with EDS) present in 4% of
middle aged men and 2% of women (Young et al 2002)
• OSA is associated with neurocognitive dysfunction,
cardiovascular disease, insulin resistance, dyslipidemia,
motor vehicle and occupational accidents
• OSA associated with metabolic syndrome (abdominal
obesity, dyslipidemia, impaired glucose tolerance,
hypertension) but causal link not proven
6. Obesity and OSA
• About 70% of those with OSA are obese (Malhotra
et al 2002)
• Prevalence of OSA in obese men and women
is about 40% (Young et al 2002)
• Higher BMI associated with higher prevalence
– BMI>30: 26% with AHI>15, 60% with AHI>5
– BMI>40: 33% with AHI>15, 98% with AHI>5
(Valencia-flores 2000)
7. Obesity and OSA
• Total body weight, BMI, and fat distribution all
correlate with odds of having OSA
– Every 10 kg increase in weight increases risk by 2X
– Every increase in BMI by 6 increases risk by 4X
– Every increase in waist or hip circumference by 13
to 15 cm increases risk by 4X (Young et al 1993)
8. Obesity as a Risk Factor For OSA:
Structural Factors
• Airway obstruction occurs when the nasopharynx and
oropharynx are occluded by posterior movement of the
tongue and palate against the posterior pharyngeal wall
• Narrower airways are more easily collapsible and prone to
airway occlusion
• Obese people have extrinsic narrowing of the area
surrounding collapsible region of the pharynx and regional
soft tissue enlargement (Fleetham 1992)
• Increased fat deposits posteriolateral to oropharyngeal
airspace at level of soft palate, in the soft palate, and in
submental area (Horner et al 1989)
10. Obesity as a Risk Factor For OSA:
Structural Factors
• Distribution of fat is an important correlate
• Fat accumulation in the central, android (apple
shape), and upper body correlate with metabolic
syndrome, atherosclerosis, and OSA
• Waist circumference more important than BMI,
weight, or total fat content
• Increased waist circumference predicts OSA even
in non-obese (Grunstein 1993)
11. Obesity as a Risk Factor For OSA:
Structural Factors
Apple shape is riskier than Pear shape
12. Central Obesity and OSA
• Anatomic respiratory effects: reduced upper
airway size secondary to mass effect of the
large abdomen on the chest wall and tracheal
traction (Pillar, Shehadeh 2008)
• Endocrine effects: The concept of leptin and
ghrelin
13. Leptin
• Leptin is an appetite suppressant
• Leptin associated with satiety, weight control, and fat
distribution (central obesity)
• Obese and pts with OSA (independently) have high leptin due
to leptin resistance rather than as a result of leptin deficiency
• Positive correlation between leptin and AHI in OSA
• Sleep deprivation/disordered sleep causes decreased leptin
making you feel more hungry (Patel et al 2004)
• Treatment of OSA with CPAP decreases leptin (after 2
months) and ghrelin levels (after 2 days) (Harsch et al 2003)
• ?? Treating OSA could lead to decreased appetite
14. Ghrelin
• Ghrelin is an appetite stimulant
• Ghrelin levels increase after weight loss
• Ghrelin levels higher in OSA pts
• Treatment of OSA may reduce ghrelin levels
leading to decreased appetite
16. Obesity, OSA, Disease conditions, and
Disease mechanisms
• Obesity and OSA are associated with common disease conditions with
overlapping pathogenesis and disease mechanisms, but causation still
unclear
Diseases Mechanisms
– Heart failure - Leptin
– Pulmonary htn - Insulin resistance
– Chronic CAD - Hypercoagulability
– Cerebrovasc.disease - Inflammation
– Hypertension - Sympathetic activity
– MI - Genetics
– Stroke and TIA
18. Can Obesity be a consequence of OSA?
• OSA reduces physical activity and exercise
performance
• OSA reduces energy metabolism
• OSA reduces motivation (from underlying
comorbidities like depression: several studies
have found correlation between OSA and
depression) (Baran 2003)
• OSA reduces physical activity from sleepiness
(Basta 2008)
19.
20. OSA and exercise performance
• Grote and colleagues studied 1149 pts with OSA
• BP and HR at rest and during graded bicycle exercise to assess
cardiovascular reactivity in those with and w/o OSA
• Results: Maximal exercise capacity was less in those with OSA
• Conclusions: OSA associated with reduced physical work capacity
and modified hemodynamic response to exercise
• Aguillard and colleagues studied 32 patients with OSA
• Performed PSGs and maximal exercise test which served as an
objective indicator of fatigue. Also completed FSS as subjective
measure of fatigue
• Conclusions: Those with poor quality sleep or inadequate
amount of sleep showed higher levels of fatigue both
subjectively and objectively
21. OSA and energy metabolism
• Reduced leptin and increased ghrelin lead to increased
hunger and decreased energy metabolism
• Vanuxem and colleagues studied 11 pts with OSA
– Asked to perform maximal effort and measured on
cycloergometer
– Decrease in maximum blood lactate concentration
suggesting an impairment of glycolytic metabolism and
decrease in the rate of lactate elimination indicating a
defect in oxidative metabolism seen in those with OSA
– Conclusion: OSA linked to impaired muscle energy
metabolism
22. Treatment of Obesity and Impact on OSA
• I will focus on dietary weight loss
• Medical weight loss with appetite
suppressants like sibutramine linked to
hypertension and arrythmias so unsuitable in
OSA patients
• Surgical weight loss such as bariatric surgery
for BMI >40 or BMI>35 with comorbidities
– Multiple studies have shown significant
improvements in AHI with lap band and Roux-en-Y
23. Dietary weight loss can improve OSA
• Reduces upper airway collapse by modifying anatomy
and function
– 13% weight loss decreased nasopharyngeal airway
collapsibility in obese patients with OSA after diet. All had
decrease in AHI. (Suratt 1987)
– Improved pharyngeal and glottic fxn and significant
decrease in AHI after 26 kg weight loss in obese patients
with OSA (Rubinstein 1988)
– 14 pts with BMI>40 showed significant reduction inn neck
fat on MRI and significant decrease in AHI (24.3 to 2.9)
after 10% weight loss (Hernandez 2009)
– In 15 obese pts found 8% weight loss decreased nocturnal
oxygen desat index significantly (Kansanen 1998)
24. Dietary weight loss can improve OSA
• Impact of weight loss is greater in those with
severe OSA (AHI>30) and those higher in BMI
– In obese patients, even minimal weight loss can be
beneficial
– Thought to be related to preferential loss of visceral
fat first as oppose to subcutaneous fat which has
metabolic advantages
– Study of 34 pts with BMI<30 and mild to moderate
OSA did not show significant decrease in AHI with
weight loss in most of the group (Only 8 pts had
decrease of AHI to <5) (Lam 2007)
25. Mean change in AHI by weight change
category (Peppard et al 2000)
26. Temporary relief of OSA from weight loss?
• Sampol and colleagues studied 24 initially
obese pts
– Despite initial cure of OSA after dietary weight
loss (Ave. BMI from 31.5 to 25.9) , OSA recurred in
50% after mean f/u of 94 months, regardless of
whether they had regained weight
– This favors a clear multifactorial etiology to OSA
27. Treatment of OSA and its effect on weight
• Weight loss may be helped by CPAP in obese with
OSA in compliant vs. noncompliant (use >4 hrs)
(Loube 1997)
• 6 mo. of CPAP could reduce intra-abdominal
visceral fat and serum leptin even in absence of
weight loss (Chin, 1999)
• 2 mo. of CPAP assoc. with reduced serum leptin
in absence of weight change (Harsch 2003)
28. Treatment of OSA and its effect on weight
• Other studies showed no change in visceral fat, weight,
and serum leptin despite adherence to CPAP therapy
in obese pts with OSA (Vgontzas, 2008)
– Small studies that lacked controls
– Lacked info on dietary habits and sleep duration
• Some studies suggest possible weight gain with CPAP
(Redenius, 2008)
– BMI of 228 pts measured pre and post CPAP for one year
and compared to pts who did not receive CPAP
– CPAP assoc. with weight gain in some. None lost weight.
29. How to manage your weight
• Reducing caloric intake is the most common
form, but difficult long term
– Overall median success rate of only 15% during up to
14 yrs of observation (Ayyad 1999)
• Reducing calorie intake is most important:
portion of fat vs. protein vs. carbs doesn’t matter
in regards to weight loss, satiety, hunger, and
satisfaction (Sacks et al. 2009)
• Diet + exercise is most effective method of
weight loss recommended by most doctors
30. How to manage your weight
• Diet alone may be just as good as diet and
exercise
– Metanalysis of 25 yrs of weight loss research on diet
alone, exercise alone, vs. diet + exercise
– Concluded: 15-week diet or diet plus exercise
program, produces a weight loss of about 24 lbs, with
a 15 and 19 lb maintained loss after one year,
respectively. (Miller 1997)
• Many studies suggest diet + exercise provides
about a 20% greater weight loss initially than diet
alone
31. How to manage your weight
• Exercise alone probably doesn’t work that
well (Caudwell 2009)
– 58 obese men and women ( Ave BMI = 31.8) were
prescribed exercise to expend approximately 500
Kcal per session, five times a week at an intensity
of 70 % maximum heart rate for 12 weeks
– Significant ave. wt loss of 3.2 kg but large
variability (loss of 14.7 kg to gain of 2.7 kg)
– Differences were accounted for by calorie intake
32. Exercise is important
• Exercise can improve sleep
– Study in a group of initially inactive adults showed
that moderate intensity exercise for 12 months
significantly improved both objective (PSG results)
and subjective measures of sleep (King et al. 2008)
• Exercise in the long run allows your body to be
more efficient at burning calories
34. Conclusions
• Complex interrelationship between weight
and OSA
• OSA may lead to weight gain and weight gain
leads to OSA
• Losing weight can improve OSA
• Unclear if treating OSA leads to weight loss
although some studies show this is the case
• Diet and exercise as well as diet alone are
good weight loss techniques
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38. Insulin Resistance/DM II
• OSA pts have higher fasting bl.glucose, insulin, and
HgbA1c than weight matched controls w/o OSA (Vgontzas
2000)
• Severity correlates with severity of AHI
• Correlation is independent of central obesity
• Study showed treatment with CPAP over 4 months
improved glucose metabolism (Brooks et al 1994)
• Effects of OSA and obesity on insulin resistance are
additive
39. Hypercoagulability
• Obese pts have higher plasma prothrombotic
factors like fibrinogen, vWF, factor VII,
plasminogen activator 1 (De Pergola, 2002)
• OSA pts have the above and increased platelet
aggregation and blood viscosity (Sanner 2000, Chin 1996, Nobili
2000)
• Exercise, low fat high fiber diet, and CPAP in OSA
pts can reverse abnormal coagulation profiles (De
Pergola 2002, Sanner 2000, Chin 1996)
• Linked to states such as MI, stroke, TIA, CAD, CVD
40. Inflammation
• Obesity is an inflammatory state (Roytblat 2000), (Visser 1999)
– High CRP and IL-6
– Central obesity has higher markers
• OSA is an inflammatory state (Shamsuzzaman 2002)
– High CPR, IL-6, TNF
• OSA inflammatory state may exist independently
of obesity
• Linked to states such as MI, stroke, TIA, CAD,
Cerebrovascular disease, hypercoagulability
41. Sympathetic activity
• Pts with OSA have high sympathetic activity
when awake, with further increases in blood
pressure and sympathetic activity during sleep
• Clinically means increased risk of stroke, htn,
cardiovascular disease, TIA, cerebrovascular
disease
• CPAP decreased blood pressure during sleep
42. Genetics
• OSA has genetic linkages
– Chrom 2p, 19 p
• Obesity has genetic linkages
– Chrom 2p, 17p, 12p
• Data suggests both shared and unshared
genetic factors in OSA and obesity (Palmer 2003)
Editor's Notes
-Clarify: intervention strategy means intervention of risk factors…not treatment intervention like CPAP
-study showed: more time in stage 2 as oppose to stage 1, shorter sleep latency, less awakenings at night, feeling more rested in the AM, higher scores on the pittsburgh sleep quality index
-