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Sleep apnoeas

Sleep disorders and obesity

Most bariatric patients do not have OSAS
Little evidence to suggest that surgery “cures” the condition
Dr Alwyn Foden

Obstructive sleep apnoea syndrome (OSAS) is often associated with obesity, however, according to Dr Alwyn Foden Consultant Respiratory Physician, County Durham and Darlington NHS Trust, there is little evidence to suggest obesity is a predisposing factor.

He also said that in his experience most bariatric patients do not have OSAS and there was little evidence to suggest that surgery “cures” the condition.

Speaking at the 1st Annual Durham & Darlington Obesity & Bariatric Symposium, he outlined the prevalence of sleeping problems with one in three American adults experiencing sleep disorders. Sleep disorders are estimated to cost the US economy $100 billion per year.

“There is more to sleep medicine than snoring and possible associated apnoeas,” said Dr Alwyn Foden consultant respiratory physician, County Durham and Darlington NHS Trust. “And if they are not treated they are costly and dangerous.”

According to Foden, there are huge variety of sleep disorders including dyssomnias (intrinsic and extrinsic sleep disorders) parasomnias (arousal disorders, sleep-wake transition disorders) and sleep disorders with medical conditions (mental, neurological and other medical disorders).

OSAS (an intrinsic sleep disorder) is defined as daytime sleepiness (DTS) not explained by other factors with two or more of loud snoring, choking/gasping during sleep, recurrent nocturnal awakening.

The incidence of OSAS in the US and Europe is estimated to be between 25-40% of the adult population, although the condition is thought to be largely underdiagnosed with only one in four patients having a diagnosis.

OSAS is the most common sleep disorder in males (males are seven times more likely to have the condition than females), often presenting with hypertension and diabetes, whereas insomnia is the most common sleep disorder in females.

Despite the association of OSAS with obesity, Foden said there is some contention as to whether weight is a predisposing factor for OSAS (Douglas et al [Eur Respir J. 1999 Feb;13[2]:398-402] and Stradling [Thorax. 1991 Feb;46[2]:85-90]).

However, there are associated links between obesity and daytime sleepiness, insomnia, uncontrolled diabetes, heart failure and hypothyroidism.

Treatment

Regarding treatment, Foden there is no evidence that managing behavioural (eg. diet) and environmental factors to improve sleep disorders helps. In addition, he said that there is no good evidence to suggest that weight loss helps, although he acknowledged that it could help morbidly obese patients.

“There are no randomised trials that show weight loss, sleep hygiene and exercise are effective in OSAS, as shown by a Cochrane Review in 2001,” he said. “Alcohol and sedative avoidance have been shown to both potentiate airway closure via enhanced airway collapsibility or depressed arousal.”

Clinical approach

When undertaking a clinical diagnosis, he said it is important to differentiate DTS from tiredness and exclude other causes of sleepiness. It is also essential to look for enlarged tonsils, a small jaw, nasal congestion, chronic obstructive pulmonary disease, asthma, respiratory failure and heart failure.

The Epworth Sleepiness Score (ESS), described by Johns et al (Sleep: 1991; 11:430-36), is a useful but not very sensitive scoring system, said Foden. ESS uses a scale of 0 to 3 to rate eight common activities, giving a maximum possible score of 24. Johns et al said a score >11 was suggestive of sleep apnoea, although it is now accepted that a patient can have a low ESS score but have a high apnea-hypopnea index in some patients.

Bariatric surgery

Foden also highlighted the paucity of evidence supporting the notion that bariatric surgery alleviates OSAS. “In a recent review of bariatric surgery by Hng Kn and Ang (Clin Medicine 2012, vol 12/5:435–440), the authors noted in the introduction that there is an epidemic of obesity and that it causes OSAS amongst a host of other conditions. However, OSAS is not mentioned in the paper again,” he said.

A double blind randomised sham controlled trial (Sivam S et al. Eur Respir J 2012; 40:913–918) showed no change in abdominal adipose tissue distribution after eight weeks of therapeutic continuous positive airway pressure (CPAP).

Although another study following patients up for two years post-bariatric surgery showed a significant decrease in OSAS symptoms and snoring (Grunstein RR et al. Sleep 2007; 30 (6): 703 – 710)

“In our experience, a lot of patients awaiting bariatric surgery don’t have OSAS, as evidenced by sleep studies even with high ESS,” said Foden. “Those that lose a lot of weight after bariatric surgery have a marked improvement in snoring, but the OSAS is not cured although it is easier to control. Obesity hypoventilation, without OSAS, would appear to be cured.”

Any patient that the bariatric service or the GP thinks might have a sleep related breathing disorder is referred to the Foden's Sleep Clinic. As bariatric surgery is likely to take place all patients have sleep studies and if the study is positive for OSAS, they are prescribed a nasal CPAP regimen. Patients are them followed up to and beyond the surgery.

“Those that are positive for OSAS before surgery are probably going to be on CPAP for a long time but hopefully with lower pressures,” he said. “If the snoring doesn’t improve with weight loss we will refer them to the rhinology service.”

He concluded by stating that sleep medicine includes a lot more conditions than OSAS, and treating the disorders is cost effective, as is treating obesity.

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