FIG. 9:  As a syndrome, CSA is not well defined.  CSA is usually diagnosed when the apnea-hypopnea index (AHI) is ≥5 and >50% of the patient’s AHI is central.  However there is marked heterogeneity in central events and breathing patterns, and little is known about the symptoms, risk factors, and other information that may define the syndrome. 

We know that the usual risk factors seen in patients with OSA do not really apply to patients with Op-CSA.  From the limited number of studies available,^[3,5,6,9] it appears that simultaneous use of CNS-active medications, such as benzodiazepines and antidepressants, may affect the severity of CSA in terms of increasing the AHI, but there are insufficient data on other medications or other active agents, such as alcohol or muscle relaxants to understand what they may do.

In terms of demographic factors, opioid users who are leaner (BMI <30) appear to experience less severe apneas and hypopneas than users who are obese.^[4] However, while this relationship with non-obese status is interesting, it has not been thoroughly investigated.  It has been speculated that the increase in central apneas in patients with lower BMI may arise because the opioids are generally prescribed in dosages that are not weight based, so it is possible that patients with lower BMIs may have relatively higher circulating doses compared to patients with greater BMIs. 

Finally, women taking chronic opioids have also been found to have a greater risk for CSA, even when matched for BMI and age with men who are taking equivalent doses of opioids.