American Journal of Hypertension 31(8) August 2018 857 REVIEW Sleep Disorders, Including Sleep Apnea and Hypertension Emer Van Ryswyk, 1 Sutapa Mukherjee, 1,2 Ching Li Chai-Coetzer, 1,2 Andrew Vakulin, 1 and R. Doug McEvoy 1,2 There is mounting evidence for an association between sleep disorders and hypertension. In obstructive sleep apnea (OSA), there are plausible biological reasons for the development of hypertension, and treatment of OSA results in modest (2–3 mm Hg), adherence-dependent decreases in blood pressure, with larger efects evident in those with resistant hypertension. However, prospective, population-based cohort studies have not yet convincingly demonstrated a link between OSA and inci- dent hypertension, and adequately powered controlled trials of CPAP for the prevention or treatment or hypertension are lacking. While asso- ciations have been identifed between short sleep duration, insomnia, restless legs syndrome (RLS), shift work, and hypertension, the causa- tive role of these conditions/circumstances is not proven, and further well-designed pathophysiological and/or interventional studies are needed. Particular emphasis should be placed on defning subgroups of hypertensive OSA patients that stand to beneft most from OSA treat- ment and in understanding the link between sleep apnea and hyper- tensive disorders of pregnancy. Well-controlled intervention studies are needed in populations with short sleep duration, insomnia, shift work sleep disorder, and RLS to confrm their putative links with hypertension. Keywords: blood pressure, hypertension, insomnia, restless legs, shift work, sleep apnea, sleep disorders. doi:10.1093/ajh/hpy082 Correspondence: Emer Van Ryswyk (emer.vanryswyk@finders.edu.au). Initially submitted May 1, 2018; accepted for publication May 10, 2018; online publication May 17, 2018. © American Journal of Hypertension, Ltd 2018. All rights reserved. For Permissions, please email: journals.permissions@oup.com 1 Adelaide Institute for Sleep Health: A Flinders Centre for Research Excellence, College of Medicine & Public Health, Bedford Park, Australia; 2 Sleep Health Service, Respiratory and Sleep Services, Southern Adelaide Local Health Network (SAHLN), Mark Oliphant Building, Bedford Park, Australia. Tere is considerable evidence for an association between sleep disorders and hypertension. However, uncertainty remains as to the extent to which sleep disorders cause hypertension, and to what degree the treatment of sleep dis- orders is benefcial for blood pressure (BP) reduction. Tis review presents the latest research on the link between sleep disorders and hypertension, focusing on results from epidemiological studies and potential underlying patho- physiological mechanisms. Areas for further research and clinical change are highlighted. OSA AND HYPERTENSION Epidemiology Results from epidemiological studies investigating the association between obstructive sleep apnea (OSA), the most common type of sleep-disordered breathing (SDB), and hypertension have been inconsistent. While major cross-sectional studies have found an association between the 2 conditions, 1–3 conficting results have arisen from pro- spective studies. 4–7 Te Sleep Heart Health Study (SHHS), one of the largest community-based multicenter cross-sec- tional studies (6,152 participants, ≥40 years, 53% female), found an increased odds ratio (OR) of 1.37 (95% con- fdence interval, 1.03–1.83) for hypertension for those with severe OSA (compared with those without OSA, i.e., apnea–hypopnea index, AHI < 1.5/hour) afer adjusting for confounders. 1 In the same study, when comparing highest and lowest categories of sleep time with oxygen saturation <90% (≥12% vs. <0.05%), the adjusted OR for hypertension was 1.46 [1.12–1.88]. In contrast, difering results have emerged on the associa- tion between OSA and hypertension from prospective stud- ies. 4–7 Te Wisconsin Sleep Cohort Study (n = 709) indicated that there was a dose–response association between SDB at baseline and the presence of new-onset hypertension 4 years later that was independent of known confounding factors. 4 Similarly, the Zaragoza Sleep Cohort Study (n = 1,889), a prospective observational study of patients with SDB (median follow-up 12.2 years), found that in comparison with their control group (participants without OSA), those with untreated OSA had an increased adjusted risk of new- onset hypertension, and CPAP-treated OSA was associated with a decreased adjusted risk of hypertension. 7 However, the Vitoria sleep cohort found no association between OSA and incidence of hypertension in the 1,557 participants who completed follow-up at 7.5 years (afer adjustment for confounding factors). 6 Furthermore, 5-year follow-up of the SHHS found that in 2,470 participants who did not have hypertension at baseline, adjustment for BMI resulted in AHI no longer being a signifcant predictor of incident hypertension. 5 Reasons for these conficting results require further investigation. Te potential for OSA to cause hypertension is supported by studies of OSA treatment on BP. A 2015 meta-analysis Downloaded from https://academic.oup.com/ajh/article-abstract/31/8/857/4997027 by guest on 15 June 2020