Two studies presented at the annual Congress of the European Respiratory Society (ERS) in Stockholm have revealed that obesity surgery (known to specialists as bariatric surgery) may have important advantages beyond its primary objective of major weight loss. It can significantly reduce, or even eliminate, interruptions to breathing (apnoea) during sleep. Sleep apnoea can cause snoring and is a recognised risk factor for cardiovascular disease.

It is common knowledge that obesity now represents a major public health problem throughout the world and is widely forecast to grow steadily worse over time. Aesthetics are by no means the only issue here, since extra weight impacts negatively on health as a whole and on various specific processes within the body. In respiratory medicine, it has for example significant repercussions: it has long been known to be associated with severe sleep disturbances, particularly with obstructive sleep apnoea, whose best-known consequence is snoring.

In obese subjects, the airway is narrowed by fatty tissue around the neck. When the throat muscles relax during sleep, this narrows this sector of the airway even further and in some cases can temporarily obstruct it completely when the muscles are entirely relaxed.
This change in calibre leads to a reduction in respiratory flow (known by the technical term of hypopnoea), or by a complete interruption to breathing (apnoea). The obstruction clears only when the drop in blood oxygen and the corresponding rise in carbon dioxide reach the warning levels and set off the breathing reflex.
The resumption in breathing following an apnoeic pause is generally very noisy, and this is the commonest type of snoring. Given other deleterious consequences of apnoea, it is important for snorers to try and lose weight, generally through a healthier lifestyle, with regular physical activity and a lower-calorie diet.

More snorers than expected

Yet these measures, it is acknowledged, are not enough for morbidly obese subjects to attain a healthy body weight. Hence a number of surgical techniques, known collectively as "bariatric surgery", have been used on such patients, often providing excellent results in terms of weight reduction. The two studies presented in Stockholm now show that weight loss is not by any means the only benefit of this type of surgery, and that bariatric surgery patients also benefit from improved sleep quality.

This can be seen clearly from the results presented to the Congress by Ana Maria Fortuna, of the Department of Respiratory Medicine, Santa Creu y Sant Pau Hospital, Barcelona. "We determined the frequency of obstructive sleep apnoea syndrome (OSAS) in 31 obese patients prior to bariatric surgery and then measured the benefits in terms of reduced sleep apnoea resulting from the weight loss linked to the surgery", Fortuna told the Congress. The subjects' initial body mass index (BMI) averaged 47, which, for a person 170 cm in height would correspond to a weight of approximately 135 kg, instead of the 72 kg that would be normal for this height.

The first thing that the Barcelona researchers pointed out was that a very large proportion of the subjects - more than expected - suffered from apnoea. In fact, 19 of the 31 patients (a prevalence of 61%) were found to suffer from OSAS, although only four of them had been diagnosed prior to the study. As is typically the case, proportionally more men than women had OSAS (nine of the ten men participating in the study).

Breathing interrupted for twenty to forty minutes each night

The Catalan team was also struck by the severity of the OSAS among the morbidly obese patients.
"Of the nineteen patients diagnosed, fourteen had an apnoea/hypopnoea index (AHI) of more than 15, which mean that they stopped breathing for over ten seconds at least fifteen times per hour. That index was as high as thirty for eleven of the patients", Fortuna explained.
A simple calculation shows that, in an eight-hour night, these subjects stop breathing for at least ten seconds between 120 and 140 times, which is the equivalent of spending a total of twenty to forty minutes without breathing each night!

Focusing on the fourteen patients with the most severe OSAS, the Barcelona team tried to identify how their apnoea had evolved following the obesity surgery, once their weight had stabilised at the eighteen-month or two-year mark. At that stage, their BMI had fallen to between 25 and 30, which meant that most of the subjects were no longer obese, but merely overweight. The operation had helped them to lose between 35 and 65 kg.
As Fortuna and her team told the Congress, the weight loss had significantly improved the apnoea symptoms and the severity of OSAS: "Following surgery, the apnoea/hypopnoea index (AHI) fell from 59 to nine on average, with only three patients presenting an AHI above 15".

So the Barcelona study's conclusion is very clear. Not only have the patients undergoing bariatric surgery a high prevalence of OSAS, but obesity surgery reduces apnoea symptoms, and can indirectly put an end to snoring. It also improves OSAS, which means that these patients no longer require treatment for sleep disturbances. "These factors point to a need for routine screening of OSAS in such obese patients", concludes Fortuna's team.

Three to four times less apnoea two years later

The other study presented to the ERS Congress on the subject of apnoea was carried out by a team in Salt Lake City (USA), led by James Walker, of the Intermountain Sleep Disorders Centre at LDS Hospital. The subjects, 22 men and 131 women, were also morbidly obese (with an average Body Mass Index of 47-48) and almost all of them presented obstructive sleep apnoea syndrome (95% of the men and 83% of the women).

Like the Barcelona team, Walker and his colleagues initially registered substantial weight loss among their subjects following bariatric surgery. "On average, 26 months after surgery, the weight loss was of the order of 55 kg for men, taking them to an average weight of 112 kg, and 43 kg for women, who attained an average weight of 84 kg", Walker stated. "Importantly, this weight loss reduced the number of apnoeas/hypopnoeas for both men and women, respectively from 40 to 10/hour and from 20 to 7/hour", he continued.
So the bariatric surgery made it possible to normalise breathing and blood oxygen levels during sleep.
Better still, as the Salt Lake City investigators told the Congress, post-surgery the patients had a reduced level of insulin resistance, an element of metabolic syndrome that is known to be linked to cardiovascular risks and diabetes.

European Respiratory Society