Primary Aldosteronism and Obstructive Sleep Apnea: A Cross-Sectional Multi-Ethnic Study.

In the current issue of Hypertension, Mulatero et al on behalf of the HYPNOS study investigators (Hypertensives With Primary Aldosteronism and Osas) report on the prevalence of primary aldosteronism (PA) in patients with objectively confirmed obstructive sleep apnea (OSA) and the prevalence of OSA in unselected patients with PA. Unexpectedly, the prevalence of PA in OSA patients did not differ significantly from that observed previously in the general hypertensive population. Increased aldosterone levels, affecting not only blood pressure (BP) but also fluid homeostasis, might contribute to the link between OSA and hypertension. This concept was supported by earlier studies assessing OSA severity and aldosterone excess, the effect of continuous positive airway pressure treatment on aldosterone levels as well as the impact of mineralocorticoid receptor antagonists administration on OSA severity. Moreover, the interplay between OSA and PA was also evaluated, and the bidirectional relationship between these 2 clinical entities has been acknowledged by the Endocrine Society that advocates screening of PA in OSA hypertensive patients. The HYPNOS study challenges the current recommendation of the Endocrine Society guideline that all OSA patients should be screened for PA, irrespective of the grade of hypertension. These novel and important findings presented by HYPNOS study investigators raise some questions, comments, and suggestions for future studies. First, while the study was based on state-of-the-art screening, confirmatory and subtyping tests for PA, it was somewhat limited in terms of cardiovascular phenotyping. Current hypertension guidelines stress the role of out-of-the-office BP measurements, which were not applied in the HYPNOS study. Furthermore, it would benefit from the assessment of hypertension-mediated target organ damage, which is more prevalent in both OSA and PA patients. Therefore, it remains to be determined whether the concomitant presence of an altered diurnal BP profile and cardiovascular damage could identify a subcohort of OSA patients, which would benefit from the PA screening. Second, sleep apnea severity was denoted by an apneahypopnea index (AHI), which reflects an average number of sleep apneic and hypopneic episodes per hour of sleep. In the HYPNOS study, AHI was derived from both polysomnography-based recordings and from cardiorespiratory studies. Importantly, polygraphy-derived AHI (known as respiratory event index) is ≈30% lower when compared with the corresponding AHI calculated during polysomnography. Consequently, the combined interpretation of these 2 indices is challenging, especially when grouping the patients to different severity classes. Furthermore, cardiorespiratory polygraphic studies are not designed for OSA screening in unselected and particularly symptomless patients. Finally, AHI may be a suboptimal marker describing the link between OSA severity and cardiovascular disease, and other hypoxia-related indices might provide better cardiovascular risk assessment. Third, the HYPNOS study demonstrated that the relationship between AHI and aldosterone serum levels is evident only in whites but not in Chinese OSA patients. This finding warrants the need to test such relationship in other ethnic groups. Such a discrepancy should be taken under consideration before any update of the universal endocrine guidelines for PA screening. A possible scenario of a postulated guidelines update may include specific recommendations dedicated to screening different ethnic groups. Fourth, the study might have implications for other endocrine disorders. Although there are gaps in evidence the International Diabetes Federation advocates bidirectional screening for both diabetes mellitus and OSA to ensure that a person presenting one condition is considered for the other. This clinical standard was based on seminal studies, for example, Wisconsin Sleep Cohort Study where only 14.7% of subjects with AHI ≥15 (moderate-to-severe disease) had comorbid diabetes mellitus. Future studies might re-assess the current recommendation taking into account cost-effectiveness of such an approach. Finally, one should remember that the Endocrine Society guidelines issued in 2016 extended recommendations for PA screening not only to OSA hypertensive patients but also favored PA screening in newly diagnosed hypertensive patients with BP values exceeding 150/100 mm Hg (a 10 mm Hg lower threshold as compared with previous guidelines). Since more severe and frequently difficult to manage The opinions expressed in this article are not necessarily those of the American Heart Association. From the Department of Hypertension and Diabetology, Faculty of Medicine and Center of Translational Medicine, Medical University of Gdańsk, Poland. The online-only Data Supplement is available with this article at https:// www.ahajournals. org/doi/suppl/10.1161/HYPERTENSIONAHA. 119.13935. Correspondence to Jacek Wolf, Department of Hypertension and Diabetology, Medical University of Gdansk, Debinki 7 str, 80-211 Gdansk, Poland. Email jacek.wolf@gumed.edu. pl Primary Aldosteronism and Obstructive Sleep Apnea A Cross-Sectional Multi-Ethnic Study