Singh, Prachi

Abstract Background Obstructive sleep apnea (OSA) is a risk factor for hypertension and some evidence suggests this risk may not be mitigated with positive airway pressure. Low-intensity statin therapy can modestly reduce blood pressure (BP). In this exploratory analysis, we examined if six months of high-intensity statin therapy could lower resting or ambulatory BP in patients with OSA. Methods 39 patients with OSA (13F, age = 49 ± 9yrs, body mass index = 32.9 ± 4.2kg/m2, apnea-hypopnea index = 22.2 ± 12.4 events/hour) were randomized to high-intensity atorvastatin or placebo. BP was assessed using seated, “office” measurements and in 20-minute intervals over 24 consecutive hours at three timepoints (baseline, three- and six-months post-randomization). Participants maintained a diary denoting sleep and wake times for analysis. Changes (Δ) in BP from baseline were assessed and adjusted for adherence to participants’ intervention (atorvastatin or placebo) as well as to their treatment for OSA (yes or no). Results There were no between-group differences in baseline BP variables (P = .09-.96). At three months, the changes in resting (P = .74-.87), 24 hour mean (P = .54-.96), daytime (P = .70-.96), nor nighttime (P = .74-.96) BP did not differ between groups. Similarly, the changes in resting (P = .23-.92), 24 hour mean (P = .51-.82), daytime (P = .17-.78), and nighttime (P = .51-1.00) BP did not differ between groups following six months of their respective intervention. Conclusions Our data suggest that high-intensity atorvastatin does not lower resting or ambulatory BP in patients with OSA relative to a placebo. Thus, it does not appear that atorvastatin is a viable adjunct intervention for BP reduction in patients with OSA. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03308578.

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder and an established risk factor for cardiovascular diseases, including hypertension. The pathogenesis of elevated blood pressure (BP) in OSA is multifactorial, including sympathetic overdrive, vascular aberrations, oxidative stress, inflammation, and metabolic dysregulation. Among the mechanisms potentially involved in OSA-induced hypertension, the role of the gut microbiome is gaining increasing attention. Perturbations in the diversity, composition, and function of the gut microbiota have been causally linked to numerous disorders, and robust evidence has identified gut dysbiosis as a determinant of BP elevation in various populations. In this brief review, we summarize the current body of literature on the implications of altered gut microbiota for hypertension risk in OSA. Data from both preclinical models of OSA and patient populations are presented, and potential mechanistic pathways are highlighted, along with therapeutic considerations. Available evidence suggests that gut dysbiosis may promote the development of hypertension in OSA and may thus be a target for interventions aimed at attenuating the adverse consequences of OSA in relation to cardiovascular risk.

We examined the effect of intermittent hypoxia (IH, a hallmark feature of sleep apnea) on adipose tissue lipolysis and the role of endothelin-1 (ET-1) in this response. We hypothesized that IH can increase ET-1 secretion and plasma free fatty acid (FFA) concentrations. We further hypothesized that inhibition of ET-1 receptor activation with bosentan could prevent any IH-mediated increase in FFA. To test this hypothesis, 16 healthy male participants (32 ± 5 yr, 26 ± 2 kg/m2) were exposed to 30 min of IH in the absence (control) and presence of bosentan (62.5 mg oral twice daily for 3 days prior). Arterial blood samples for ET-1, epinephrine, and FFA concentrations, as well as abdominal subcutaneous adipose tissue biopsies (to assess transcription of cellular receptors/proteins involved in lipolysis), were collected. Additional proof-of-concept studies were conducted in vitro using primary differentiated human white preadipocytes (HWPs). We show that IH increased circulating ET-1, epinephrine, and FFA ( P < 0.05). Bosentan treatment reduced plasma epinephrine concentrations and blunted IH-mediated increases in FFA ( P < 0.01). In adipose tissue, bosentan had no effect on cellular receptors and proteins involved in lipolysis ( P > 0.05). ET-1 treatment did not directly induce lipolysis in differentiated HWP. In conclusion, IH increases plasma ET-1 and FFA concentrations. Inhibition of ET-1 receptors with bosentan attenuates the FFA increase in response to IH. Based on a lack of a direct effect of ET-1 in HWP, we speculate the effect of bosentan on circulating FFA in vivo may be secondary to its ability to reduce sympathoadrenal tone.

Although insufficient sleep is associated with increased cardiovascular risk, evidence of a causal relationship is lacking. We investigated the effects of prolonged sleep restriction on 24-hour ambulatory blood pressure (BP) and other cardiovascular measures in 20 healthy young participants (aged 23.4±4.8 years, 9 females), who underwent a randomized, controlled, crossover, 16-day inpatient study consisting of 4 days of acclimation, 9 days of sleep restriction (4 hours of sleep/night) or control sleep (9 hours), and 3 days of recovery. Subjects consumed a weight maintenance diet with controlled nutrient composition throughout. A 24-hour BP (primary outcome) and cardiovascular biomarkers were measured repeatedly. Polysomnographic monitoring was continuous. Comparing sleep restriction versus control sleep, 24-hour mean BP was higher (adjusted mean difference, day 12: 2.1 mm Hg [95% CI, 0.6–3.6], corrected P =0.016), endothelial function was attenuated ( P <0.001), and plasma norepinephrine increased ( P =0.011). Despite increased deep sleep, BP was elevated while asleep during sleep restriction and recovery. Post hoc analysis revealed that 24-hour BP, wakefulness, and sleep BP increased during experimental and recovery phases of sleep restriction only in women, in whom 24-hour and sleep systolic BP increased by 8.0 (5.1–10.8) and 11.3 (5.9–16.7) mm Hg, respectively (both P <0.001). Shortened sleep causes persistent elevation in 24-hour and sleep-time BP. Pressor effects are evident despite closely controlled food intake and weight, suggesting that they are primarily driven by the shortened sleep duration. BP increases are especially striking and sustained in women, possibly suggesting lack of adaptation to sleep loss and thus greater vulnerability to its adverse cardiovascular effects.

Telomere length (TL) is associated with cardiovascular disease (CVD) and cancer. Obstructive sleep apnea (OSA) is also linked to higher risk of CVD and cancer, and to TL. We investigated the association between TL and risk of major adverse cardiac events (MACE) and cancer in OSA patients. We studied 210 individuals undergoing sleep-related studies between 2000 and 2007. Baseline characteristics and follow-up data (available in 164 subjects) were obtained from clinic records. Incidence rates were calculated for the entire group and by OSA status. Hazard ratios were calculated to estimate effects of OSA and TL on risk of MACE and cancer. In total, 32 individuals (20%) developed MACE and/or cancer during 12.7-year follow-up. The OSA group had a higher likelihood of cancer (16.0 vs. 4.9 events per 1000 person-years, P = 0.044) but no clear evidence of an elevated incidence of MACE (10.8 vs. 4.8 events per 1000 person-years, P = 0.293) compared to the non-OSA group. There was no association between TL and MACE- (HR = 1.01, 95% CI 0.78–1.28), or cancer-risk (HR = 1.18, 95% CI 0.96–1.43). Our study warrants further investigation of any modulating effect of OSA on TL and the risk of MACE and cancer.

Background Excessive daytime sleepiness ( EDS ), a common symptom among patients with sleep‐disordered breathing, is closely associated with the development of cardiovascular diseases, but its long‐term prognostic value is not completely understood. The aim of this study was to investigate whether EDS would be an independent prognostic factor after myocardial infarction. Methods and Results We prospectively recruited 112 post–myocardial infarction patients. The Epworth Sleepiness Scale was completed before polysomnography, and EDS was defined as a score ≥11. After exclusion of 8 patients who accepted treatment with continuous positive airway pressure, 104 patients were followed up for 48 months. The primary composite end point was major adverse cardiac events. Patients with EDS had higher rates of major adverse cardiac events (48.4% versus 27.4%, χ 2 =5.27, P =0.022) and reinfarction (29.0% versus 5.5%, χ 2 =13.51, P =0.0002) compared with those without EDS . In the Cox proportional hazards model, patients with EDS had 2.15 times (95% confidence interval, 1.08–4.18; P =0.030) higher crude risk of major adverse cardiac events, with prognostic significance persisting after adjusting for age, diabetes mellitus, depression, left ventricular ejection fraction, apnea–hypopnea index, and nocturnal nadir oxygen saturation (hazard ratio: 2.13, 95% confidence interval, 1.04–4.26, P =0.039). Furthermore, among participants with moderate to severe sleep‐disordered breathing, the presence of EDS was associated with higher risk of major adverse cardiac events than those without EDS , after adjusting for age and nadir oxygen saturation (hazard ratio: 3.17, 95% confidence interval, 1.22–7.76, P =0.019). Conclusions EDS may be an independent prognostic factor of adverse outcome in post–myocardial infarction patients with moderate to severe sleep‐disordered breathing. Evaluation of EDS may shed new light on risk stratification and identify treatment responders for this patient population.

Obstructive sleep apnea (OSA) is associated with cardiometabolic diseases. Telomere shortening is linked to hypertension, diabetes mellitus, and cardiovascular diseases. Because these conditions are highly prevalent in OSA, we hypothesized that telomere length (TL) would be reduced in OSA patients. We identified 106 OSA and 104 non-OSA subjects who underwent polysomnography evaluation. Quantitative PCR was used to measure telomere length in genomic DNA isolated from peripheral blood samples. The association between OSA and TL was determined using unadjusted and adjusted linear models. There was no difference in TL between the OSA and non-OSA (control) group. However, we observed a J-shaped relationship between TL and OSA severity: the longest TL in moderate-to-severe OSA [4,918 ± 230 (SD) bp] and the shortest TL in mild OSA (4,735 ± 145 bp). Mean TL in moderate-to-severe OSA was significantly longer than in the control group after adjustment for age, sex, body mass index, hypertension, dyslipidemia, and depression (β = 96.0, 95% confidence interval: 15.4–176.6, P = 0.020). In conclusion, moderate-to-severe OSA is associated with telomere lengthening. Our findings support the idea that changes in TL are not unidirectional processes, such that telomere shortening occurs with age and disease but may be prolonged in moderate-to-severe OSA. NEW & NOTEWORTHY Here, we show that moderate-to-severe obstructive sleep apnea is associated with longer telomeres, independent of age and cardiovascular risk factors, challenging the hypothesis that telomere shortening is a unidirectional process related to age/disease. A better understanding of the mechanisms underlying telomere dynamics may identify targets for therapeutic intervention in cardiovascular aging/other chronic diseases.