Sleep apnoea: a brief guide for pharmacists

Obstructive sleep apnoea (OSA) is a common sleep disorder associated with a number of adverse metabolic health consequences. However, many patients with OSA remain undiagnosed simply because a major symptom of the condition is snoring, which is frequently dismissed by bed partners as an annoyance rather than a cause for concern.

Types of sleep apnoea

Sleep apnoea is characterised by upper airway obstruction during sleep, leading to transient asphyxia and hypoxia. These repetitive stoppages of the normal breathing cycle during sleep can occur for anywhere between 10 and 30 seconds at a time and arise from either a complete collapse of the upper airways (‘apnoea’) or a narrowing (‘hypopnoea’) of these airways.

There are two main forms of sleep apnoea: central and obstructive. The central type is far less common and develops because the brain is unable to provide effective signals to the breathing muscles. It can be caused by brain-related problems such as a stroke or tumours, other conditions (e.g. heart failure) and even by drugs with a central action, including opioids, gabapentin and valproic acid.

In contrast, obstructive sleep apnoea (OSA) arises because of an increase in the volume of the upper airway tissue, mainly in the lateral pharyngeal, soft palate and tongue areas. This enlargement of tissue volume effectively narrows the airway, making it more prone to collapse and occlusion during sleep. A similar thickening of the pharyngeal walls is seen in those with obesity which, not surprisingly, is an important risk factor for OSA.

OSA: Risk factors and prevalence

Alongside obesity, recognised risk factors for OSA include:

• Increasing age 
• Family history
• Being male 
• Neck circumference greater than 40.6cm
• Body mass index greater than 30
• Waist circumference above 102cm.

Globally, OSA has been estimated to affect 936 million people between the ages of 30 and 69 years. The prevalence of OSA in the UK is less clear. According to NICE, in 2024, there are an estimated 2.5 million adults affected by the condition. However, writing in a 2020 paper in The Lancet, the authors estimated that around 8 million people in the UK might be affected.

Symptoms

Many people with OSA are probably unaware that they have the condition. Patients are often prompted to seek medical advice due to concerns expressed by bed partners or family members.

Typically, the most common symptom of OSA is snoring, reportedly affecting around 94 per cent of sufferers. However, bed partners might also have been worried by the presence of interrupted snoring, together with sudden awakenings and witnessing their partner gasping for air.

Affected individuals are liable to experience daytime sleepiness and to take regular naps. They also frequently suffer from poor concentration, mood disturbances and fatigue, easily falling asleep while reading or watching television.

Screening

Prior to a formal diagnosis, screening questionnaires can be used to raise the index of suspicion that a patient has OSA. There are several OSA screening tools available, with one such example being STOP-BANG, which is shown in Table 1.

STOP-BANG appears to do a great job at identifying those with OSA, but is much less effective in determining when someone doesn’t have the condition.

The Epworth Sleepiness Scale (ESS) can also be used as part of the patient assessment. The ESS provides a subjective rating of the extent to which patients experience daytime sleepiness, based on the chances of them dosing off in eight commonly encountered scenarios, including sitting and reading or watching television.

Although the ESS is not a useful predictor for OSA, it does serve as a guide to identifying patients who are symptomatic because of their OSA.

Diagnosing OSA

The gold standard diagnostic test for OSA is polysomnography (PSG) or a sleep study test. This is performed while an individual is asleep and undertaken at a specialist sleep centre.

PSG measures parameters including brain waves, blood oxygen levels, heart rate, as well as eye and leg movements. One metric derived from PSG is the apnoea-hypopnoea index (AHI). This has become an internationally recognised tool used to evaluate disease severity in OSA. The index provides a measure of the number of apnoea/hypopnoea episodes per hour and is calculated by dividing the total sleep time by the total number of events. 

Using the AHI, there are three different categories of OSA:

• Mild: AHI between five and 14 per hour
• Moderate: AHI between 15 and 30 per hour
• Severe: AHI greater than 30 per hour.

Interestingly, Samsung has included a sleep apnoea detecting feature in its latest smart watch. This feature, which has been approved by the US FDA, uses a built-in sensor that is able to track blood oxygen levels during a user’s sleep. The data is then used to provide an estimate of the AHI.

However, Samsung has made it clear that its smart watch feature is not diagnostic and where there is evidence of OSA, users need to consult a doctor for confirmation of the result.

Scoring

5 to 8 YES responses = High risk of OSA

3 to 4 YES responses = Intermediate risk of OSA

0 to 2 YES responses = Low risk of OSA