Screening for sleep apnoea in schizophrenia?

To the Editor

Myles et al. asserted that it was important to identify and treat obstructive sleep apnoea in patients with schizophrenia, primarily because it is associated with a considerable increase in mortality (Myles et al., 2016). In the future, this may be considered to be the correct approach, but at present, it is unclear whether continuous positive airway pressure (CPAP) reduces cardiovascular risk in the general population. A recently published randomised trial showed that CPAP led to both a reduction in day time drowsiness and improved quality of life, but there was no difference in cardiovascular morbidity (McEvoy et al., 2016).

In practice, it will be very difficult to identify patients with schizophrenia and sleep apnoea. Many patients with schizophrenia complain about drowsiness during the day because of the medication they are taking. Using a screening questionnaire is probably the only option. Myles et al. suggested using the OSA50 scale (Chai-Coetzer et al., 2011), which is validated for primary care with a cut-off point of 5. In this scale, patients with a waist circumference >102 cm (male) or >88 cm (female) score three points, and being 50 or older scores two points. This virtually guarantees that, in practice, almost every patient with long-term antipsychotic use, aged 50 and above, will reach the cut-off point of the OSA50.

The question is therefore whether every patient with long-term antipsychotic use over 50 needs further investigation for possible sleep apnoea. This presents a challenge. Overnight assessment at a specialised centre is not widely available, and overnight home monitoring (without much support) is likely to be difficult for many patients with schizophrenia.

One will need to develop a screening tool for sleep apnoea in patients using antipsychotic medication which has a reasonable sensitivity and specificity, and then investigate whether CPAP reduces cardiovascular risk and whether it is cost-effective, before formally advising that screening for sleep apnoea be included in guidelines.