Hypertension and obstructive sleep apnoea syndrome: current perspectives.

Obstructive sleep apnoea syndrome (OSAS), due to the collapse of the upper airways, is a common but still underestimated condition. The 'dose-response' type relationship between OSAS and hypertension (HT) has now been clearly proven. There are multiple mechanisms explaining this relationship, the main one being an increase in sympathetic activity during the apnoeas. HT associated with OSAS has several characteristics: high prevalence, diastolic and nocturnal predominance, and frequent non-dipper status. Furthermore, as OSAS is found in the majority of subjects with refractory HT, it should be systematically investigated in this situation. HT associated with OSAS should be tested for by means of a clinical blood pressure (BP) measurement, to which 24-h ambulatory BP monitoring (ABPM) is often added due to the fact that BP anomalies are frequently present at night. HT during OSAS is frequently associated with metabolic anomalies (for example, obesity, dyslipidaemia and insulin resistance), therefore explaining the high prevalence of metabolic syndrome in this population. The reference treatment for OSAS-nasal continuous positive airway pressure (nCPAP)-seems to be able to lower the BP of hypertensive patients, especially if the HT is severe, untreated or refractory. Moreover, the BP response to nCPAP depends on the severity of the OSAS, in particular the scale of the nocturnal desaturations, and on patient tolerance of the treatment. Optimal treatment for HT associated with OSAS has not been evidenced. Antihypertensive drugs do not change the respiratory parameters during OSAS.