We thank Dr Kawada for his thoughtful comments, and agree that obstructive sleep apnea (OSA) is an important modifiable risk factor for hypertension. Indeed, obesity and renin-angiotensin-aldosterone activation may be common in both conditions. As Dr Kawada suggests, more detailed characterization of hypertension may indeed identify subgroups in whom risk for sleep apnea and potential treatment response are greatest, helping to further delineate target populations for screening and treatment of occult sleep apnea.
Such characterization needs to be simple and cost-effective in order to be applied across large populations. As Dr Kawada suggests, use of biomarkers such as renin-angiotensin assays for risk assessment deserves further investigation and cost analysis. A second potential method is to use 24-hour ambulatory blood pressure monitoring to identify patients whose blood pressure fails to dip during sleep (“nondippers”). Ohkubo and colleagues have demonstrated an independent association between loss of nocturnal dipping and cardiovascular mortality in OSA patients, and treatment may restore the nocturnal dipping pattern. Finally, resistant hypertensive patients may be another subgroup who should be prioritized for treatment. Up to 80% of these patients may have sleep apnea, and blood pressure-lowering benefits of positive airway pressure may be particularly dramatic in this population. These data support future cost-effectiveness comparisons between additional diagnostic testing and empiric therapy in resistant hypertension patients.
The success of potential screening strategies will continue to depend on their simplicity, accessibility, and cost-effectiveness.