TABLE IV. C. 2.
Obesity as a contributing factor for OSA
| Study | Year | LOE | Study design | Study groups/age/N | Clinical end-point | Conclusion |
|---|---|---|---|---|---|---|
| Hoffstein212 | 1984 | 3b | Case–Control | Obese subjects; OSA versus non-OSA N = 19 Age=28–68 |
1. Cross-sectional area of pharynx 2. TLC (total lung capacity) to RV (residual volume) |
In obese patients with OSA, pharyngeal cross-sectional area is small and varies considerably with change in lung volume (and this change in size with change in lung volume was significantly different in the two groups) |
| Katz198 | 1990 | 3b | Cross-sectional | Canada Sleep clinic N = 123 |
PSG AHI ≥ 5 | External, internal neck circumference and degree of obesity are important predictors of OSA |
| Mezzanotte201 | 1992 | 3b | Case–control | Denver Veterans Affairs Hospital OSA and normal controls N = 25 Age = 40–46 years |
1. Supraglottic resistance 2. Genioglossal EMG 3. Minute ventilation 4. End tidal CO2 |
Neuromuscular compensation present during wakefulness from genioglossus may be lost during sleep in apneic patients |
| Shelton205 | 1993 | 3b | Case–control | Univ of Virginia Sleep clinic and control from community N = 30 Age = 23–65 |
MRI for adipose tissue volume | Adipose tissue is deposited in pharyngeal area in OSA patients, and the volume of this tissue is related to presence and degree of OSA |
| Young90 | 1993 | 2c | Cross-sectional | Wisconsin Sleep Cohort study N = 602 |
PSG AHI ≥ 5 | 1. Prevalence of OSA is 9% in women and 24% in men 2. Male sex and obesity strong risk factors 3. Increase in BMI by 1 SD is associated with three-fold increase in risk of OSA |
| Schwab200 | 1995 | 3b | Cross-sectional | Sleep Clinic at University of Pennsylvania N = 68 |
1. MRI 2. PSG RDI > 15 |
1. Lateral pharyngeal wall is larger in apneic patients 2. Wall thickness explains the largest part of variance in airway caliber |
| Peppard189 | 2000 | 2b | Prospective cohort | Population based N = 690 |
1. Percent change in AHI on PSG 2. Odds of developing moderate to severe SDB, with respect to change in weight |
1. 10% weight gain predicted an approximate 32% increase in AHI, with six-fold increase in odds of developing moderate to severe SDB 2. 10% weight loss predicted a 26% decrease in AHI |
| Stanchina203 | 2002 | 3b | Cross-sectional | Healthy individuals in Boston N = 15 Age = 24–32 |
During NREM sleep: 1. Genioglossus EMG 2. Epiglottic pressure 3. Airflow under different conditions |
Genioglossus muscle responds well during NREM sleep when hypercapnia is combined with resistive load, but is less responsive to either chemical stimuli (hypoxia, hypercapnia) or inspiratory resistive load alone |
| Young190 | 2002 | 2c | Cross-sectional | Sleep Heart Health Study N = 5615 |
In home PSG AHI ≥ 15 | Male sex, age, BMI, neck girth, snoring, and repeated breathing pause frequency were independent, significant correlates of AHI ≥ 15 |
| Schwab207 | 2003 | 3b | Case–Control | Penn Center for sleep disorder and control from community in same neighborhood N = 96 Age = 24–66 |
MRI of upper airway | Volume of lateral pharyngeal wall, total soft tissues and tongue larger in OSA than normal subjects |
| Tishler156 | 2003 | 2b | Prospective study | Cleveland family study N = 286 |
HST AHI ≥ 10 | Five-year incidence of OSA – 7.5% for moderate SDB and 16% for mild to moderate |
| Shimura213 | 2005 | 3b | Cross-sectional | Japanese sleep clinic patients N = 185 Age = 22–72 |
1. PSG AHI ≥ 5 2. CT scan for visceral and subcutaneous fat accumulation 3. Lung function 4. Leptin levels |
1. Location of body fat does not contribute to hypoventilation 2. Circulating leptin levels does not maintain alveolar hypoventilation in hypercapnic obese patients with OSA |
| Kairaitis 211 | 2007 | 5 | Animal study | Male NZ white rabbits N = 20 |
Upper airway extraluminal tissue pressure in lateral and anterior pharyngeal walls | Decrease in upper airway collapsibility due to lung volume related caudal traction |
| Foster122 | 2009 | 1b | RCT | 16 US centers (Overweight/obese with DM and OSA) N = 264 |
1. BMI 2. Waist and neck circumference 3. HbA1c |
1. The intensive lifestyle intervention (ILI) group lost more weight at 1 year than Diabetes support and education 2. ILI was associated with an adjusted decrease in AHI of 9.7 events/h |
| Flegal197 | 2010 | 2c | Cross-sectional | NHANES (National Health and Nutrition Examination Survey) population N = 5555 Age > 20 years |
BMI | In 2007–2008, the prevalence of obesity was 32.2% in men and 35.5 women |
| Ashrafian 192 | 2012 | 2a | SR(with heterogeneity) of cohort studies | Studies with metabolic interventions-33 Studies with lifestyle intervention-24 |
1. BMI 2. AHI |
Metabolic surgeries offer significant reduction in symptoms and measures of OSA by both weight dependent and independent mechanisms |
| Dixon194 | 2012 | 1b | Individual RCT (Bariatric surgery vs. conventional weight loss) | Australian Hospital-Obese patients (BMI of 35–55) and <6 months diagnosis of OSA (AHI > 20) N = 60 |
1. PSG (baseline to 2 year change in AHI) 2.Weight 3. CPAP adherence 4. Functional status |
In obese patients with OSA, bariatric surgery compared with conventional weight loss therapy did not result in a statistically greater reduction in AHI despite major differences in weight loss |
| Li202 | 2012 | 3b | Case-control | Chinese Han population (Otolaryngology Head & Neck Surgery Dept.) N = 28 |
1. MRI 2. Pharyngoscopy under general anesthesia |
OSA patients have more fat tissue adjacent to pharyngeal cavity, and the fat-deposition correlated to collapsibility |
| Peppard95 | 2013 | 2c | Cross-sectional | Wisconsin Sleep Cohort Study N = 1520 |
PSG AHI ≥ 5 and ESS>10 | Prevalence of SDB is increasing in the population (relative increases of between 14% and 55% depending on the group) |
| Chirinos 215 | 2014 | 1b | Individual RCT (Randomized to CPAP, weight loss and combined CPAP with weight loss) | Obese, moderate to severe OSA and CRP > 1 mg/L N = 181 |
1. CRP 2. Insulin sensitivity 3. Lipid levels 4. Blood pressure |
1. No difference in CRP level reduction 2. Weight loss provided incremental reduction in insulin resistance and TG level when combined with CPAP |
| Jang209 | 2014 | 3b | Cross-sectional | OSA patients from Korean Sleep Center N = 33 Age = 31–54 |
1. Facial CT 2. DISE (drug-induced sleep endoscopy) |
Parapharyngeal fat pad is associated with concentric narrowing of the retropalatal pharynx |
| Kim208 | 2014 | 3b | Case–control | University of Pennsylvania Center for Sleep and Circadian Neurobiology N = 121 |
MRI upper airway | Increased tongue volume and fat deposition at tongue base in OSA compared to controls |
| Pahkala206 | 2014 | 1b | RCT | Kuopio University Hospital, Finland N = 60 |
1. PSG 2. CT scan of upper airway |
1. Pharyngeal fat pad area was significantly larger and hyoid bone to cervical spine area longer in OSA than habitual snorers 2. Weight loss by lifestyle intervention-based program led to improvement in OSA by reducing both central obesity and pharyngeal fat pad |
| Sands204 | 2014 | 3b | Individual case–control studies | Overweight/obese without apnea (AHI < 15/h), overweight/obese with OSA (AHI ≥ 15/h) and normal weight/nonapneic N = 54 |
1. Pcrit (Pharyngeal critical closing pressure) 2. Pharyngeal muscle (greater genioglossus) EMG |
Overweight/obese without mod/severe OSA have increased (three times greater) pharyngeal muscle EMG activity during sleep responsiveness |
| Ashrafian195 | 2015 | 2a- | SR (with heterogeneity) of cohort studies (?but also has some RCT) | 19 surgical (n = 525) and 20 non-surgical (n = 825) studies | BMI and AHI before and after intervention | Surgical patients achieved a significant 14 kg/m2 weighted decrease in BMI with a 29/h weighted decrease in AHI. Non-surgical patients achieved a significant weighted decrease in BMI of 3.1 kg/m2 with a weighted decrease in AHI of 11/h |
| Ng214 | 2015 | 1b | RCT | Prince of Wales Hospital, Hongkong OSA patients with AH ≥ 15/h N = 104 |
1. HST AHI 2. ESS 3. SF-36 (Short Form Health) survey 4. BMI |
Lifestyle modification program (LMP) was more effective in reducing AHI from baseline (16.9% fewer events in LMP vs. 0.6% more events in control group with usual care) |
| Peroma193 | 2017 | 2b | Prospective cohort | Bariatric OSA patients who underwent bariatric surgery N = 132 | 1. PSG (12 months after surgery) 2. BMI 3. Neck and waist circumference |
Prevalence of OSA decreased from 71% at baseline to 44% at 12 months after surgery (p < 0.001) |
| Chen210 | 2019 | 3b | Cross-sectional | Taiwan Hospital (Otorhinolaryn- gology Dept.) N = 41 Age = 34–48 |
1. PSG AHI ≥ 5 2. Drug induced Sleep CT 3. BMI 4. Neck circumference |
Subglosso-supraglottic parapharyngeal fat pad area, independent of BMI, and neck circumference influenced severity of OSA |
| Hales196 | 2020 | 2c | Cross-sectional | US census from 2000 | BMI | 1. In 2017–2018, the age adjusted prevalence of obesity in adults was 42.4% 2. No significant differences between men and women 3. Severe obesity prevalence higher in women at 9.2% |
Abbreviations: AHI, apnea hypopnea index; BMI, body mass index; CT, computed tomography; DM, diabetes mellitus; EMG, electromyography; MRI, magnetic resonance imaging; OSA, obstructive sleep apnea; Pcrit, Pharyngeal critical pressure; PSG, polysomnography; SD, standard deviation.