Effects of acetazolamide on the sleep apnea syndrome and its therapeutic mechanism

The role of acetazolamide in sleep apnea at sea level: a systematic review and meta-analysis

STUDY OBJECTIVES

The recognition of specific endotypes as drivers of sleep apnea suggests the need of therapies targeting individual mechanisms. Acetazolamide is known to stabilize respiration at high altitude but benefits at sea level are less well understood.

METHODS

All controlled studies of acetazolamide in obstructive sleep apnea and/or central sleep apnea (CSA) were evaluated. The primary outcome was the apnea-hypopnea index.

RESULTS

Fifteen trials with a total of 256 patients were pooled in our systematic review. Acetazolamide reduced the overall apnea-hypopnea index (mean difference [MD] -15.82, 95% CI: -21.91 to -9.74, P < .00001) in central sleep apnea (MD -22.60, 95% CI: -29.11 to -16.09, P < .00001), but not in obstructive sleep apnea (MD -10.29, 95% CI: -33.34 to 12.77, P = .38). Acetazolamide reduced the respiratory related arousal index (MD -0.82, 95% CI: -1.56 to -0.08, P = .03), improved partial arterial of oxygen (MD 11.62, 95% CI: 9.13-14.11, P < .00001), mean oxygen saturation (MD 1.78, 95% CI: 0.53-3.04, P = .005), total sleep time (MD 25.74, 95% CI: 4.10-47.38, P = .02), N2 sleep (MD 3.34, 95% CI: 0.12-6.56, P = .04) and sleep efficiency (MD 4.83, 95% CI: 0.53-9.13, P = .03).

CONCLUSIONS

Acetazolamide improves the apnea-hypopnea index and several sleep metrics in central sleep apnea. The drug may be of clinical benefit in patients with high loop gain apnea of various etiologies and patterns. The existence of high heterogeneity is an important limitation in applicability of our analysis.

SYSTEMATIC REVIEW REGISTRATION

Registry: PROSPERO; Name: The effect of acetazolamide in patients with sleep apnea at sea level: a systematic review and meta analysis; URL: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020163316; Identifier: CRD42020163316.

Side effects of acetazolamide: a systematic review and meta-analysis assessing overall risk and dose dependence

Introduction

Acetazolamide (AZM) is used for various conditions (eg, altitude sickness, sleep apnoea, glaucoma), but therapy is often limited by its side effect profile. Our objective was to estimate the risk of commonly reported side effects based on meta-analyses. We hypothesised that these risks are dose-dependent.

Methods

We queried MEDLINE/EMBASE (Medical Literature Analysis and Retrieval System Online/Excerpta Medica dataBASE) up until 04/10/2019, including any randomised placebo-controlled trial in which adults received oral AZM versus placebo reporting side effects. Eligibility assessment was performed by two independent reviewers. Data were abstracted by one reviewer who verified key entries at a second time point. For side effects reported by >3 studies a pooled effect estimate was calculated, and heterogeneity assessed via I²; for outcomes reported by >5 studies effect modification by total daily dose (EMbyTDD; <400 mg/d, 400–600 mg/d, >600 mg/d) was assessed via meta-regression. For pre-specified, primary outcomes (paraesthesias, taste disturbances, polyuria and fatigue) additional subgroup analyses were performed using demographics, intervention details, laboratory changes and risk of bias.

Results

We included 42 studies in the meta-analyses (N_subjects=1274/1211 in AZM/placebo groups). AZM increased the risk of all primary outcomes (p<0.01, I² ≤16% and low-to-moderate quality of evidence for all)—the numbers needed to harm (95% CI; n_Studies) for each were: paraesthesias 2.3 (95% CI 2 to 2.7; n=39), dysgeusia 18 (95% CI 10 to 38, n=22), polyuria 17 (95% CI 9 to 49; n=22), fatigue 11 (95% CI 6 to 24; n=14). The risk for paraesthesias (beta=1.8 (95% CI 1.1 to 2.9); P_EMbyTDD=0.01) and dysgeusia (beta=3.1 (95% CI 1.2 to 8.2); P_EMbyTDD=0.02) increased with higher AZM doses; the risk of fatigue also increased with higher dose but non-significantly (beta=2.6 (95% CI 0.7 to 9.4); P_EMbyTDD=0.14).

Discussion

This comprehensive meta-analysis of low-to-moderate quality evidence defines risk of common AZM side effects and corroborates dose dependence of some side effects. These results may inform clinical decision making and support efforts to establish the lowest effective dose of AZM for various conditions.

Considering the Role of Adherence in New and Emerging Sleep Treatments

There are several novel and emerging treatments for obstructive sleep apnea (OSA), including new devices and pharmacotherapies. Long-term efficacy and adherence data for these interventions in the sleep context are lacking. Future studies exploring the long-term adherence and efficacy in novel and emerging treatments of OSA are required to fully understand the place of these treatments in treatment hierarchies. Such research also should aim to evaluate the use of these novel therapies in real-world clinical settings, because many of the studies performed to date have been done under closely monitored research populations and relatively small sample sizes.

Acetazolamide for OSA and Central Sleep Apnea: A Comprehensive Systematic Review and Meta-Analysis

BACKGROUND

Therapy options for OSA and central sleep apnea (CSA) are limited, thus many patients remain untreated. Clinically, acetazolamide is sometimes used for CSA; however, given overlapping pathophysiologic properties of OSA and CSA, we hypothesized that acetazolamide is equally effective for both types. Prior reviews focused on specific subtypes of sleep apnea, study designs, and languages, thus including few studies (typically ≤3) limiting insights.

RESEARCH QUESTION

How efficacious is acetazolamide for sleep apnea, and is its effect modified by sleep apnea type or acetazolamide dose?

STUDY DESIGN AND METHODS

We queried MEDLINE, EMBASE, and ClinicalTrials.gov from inception until March 11, 2019. Any study in which adults with OSA/CSA received oral acetazolamide vs no acetazolamide (control) that reported sleep apnea-related outcomes was eligible, independent of study design or language. Two reviewers independently assessed eligibility and abstracted data. Primary outcomes were apnea-hypopnea index (AHI) and oxygen saturation nadir. Quality of evidence (QoE) was rated with the use of Grades of Recommendation Assessment, Development and Evaluation methods.

RESULTS

We included 28 studies (13 OSA/15 CSA; N_{Subjects,Acetazolamide} = 542; N_{Subjects,Control} = 553) that enabled meta-analyses for 24 outcomes. Acetazolamide doses ranged from 36 to 1000 mg/d and treatment duration from 1 to 90 d (median, 6 d). Overall, acetazolamide vs control lowered the AHI by -0.7 effect sizes (95% CI, -0.83 to -0.58; I² = 0%; moderate QoE) that corresponded to a reduction of 37.7% (95% CI, -44.7 to -31.3) or 13.8/h (95% CI, -16.3 to -11.4; AHI_Control = 36.5/h). The AHI reduction was similar in OSA vs CSA, but significantly greater with higher doses (at least up to 500 mg/d). Furthermore, acetazolamide improved oxygen saturation nadir by +4.4% (95% CI, 2.3 to 6.5; I² = 63%; no evidence of effect modification; very low QoE) and several secondary outcomes that included sleep quality measures and BP (mostly low QoE).

INTERPRETATION

Short-term acetazolamide improved both OSA and CSA. Rigorous studies with long-term follow up are warranted to assess Acetazolamide's value for the chronic treatment of patients with sleep apnea.

CLINICAL TRIAL REGISTRATION

PROSPERO (CRD42019147504).

Effects of stabilizing or increasing respiratory motor outputs on obstructive sleep apnea

To determine how the obstructive sleep apnea (OSA) patient's pathophysiological traits predict the success of the treatment aimed at stabilization or increase in respiratory motor outputs, we studied 26 newly diagnosed OSA patients [apnea-hypopnea index (AHI) 42 ± 5 events/h with 92% of apneas obstructive] who were treated with O2 supplementation, an isocapnic rebreathing system in which CO2 was added only during hyperpnea to prevent transient hypocapnia, and a continuous rebreathing system. We also measured each patient's controller gain below eupnea [change in minute volume/change in end-tidal Pco2 (ΔVe/ΔPetCO2)], CO2 reserve (eupnea-apnea threshold PetCO2), and plant gain (ΔPetCO2/ΔVe), as well as passive upper airway closing pressure (Pcrit). With isocapnic rebreathing, 14/26 reduced their AHI to 31 ± 6% of control (P < 0.01) (responder); 12/26 did not show significant change (nonresponder). The responders vs. nonresponders had a greater controller gain (6.5 ± 1.7 vs. 2.1 ± 0.2 l·min(-1)·mmHg(-1), P < 0.01) and a smaller CO2 reserve (1.9 ± 0.3 vs. 4.3 ± 0.4 mmHg, P < 0.01) with no differences in Pcrit (-0.1 ± 1.2 vs. 0.2 ± 0.9 cmH2O, P > 0.05). Hypercapnic rebreathing (+4.2 ± 1 mmHg PetCO2) reduced AHI to 15 ± 4% of control (P < 0.001) in 17/21 subjects with a wide range of CO2 reserve. Hyperoxia (SaO2 ∼95-98%) reduced AHI to 36 ± 11% of control in 7/19 OSA patients tested. We concluded that stabilizing central respiratory motor output via prevention of transient hypocapnia prevents most OSA in selected patients with a high chemosensitivity and a collapsible upper airway, whereas increasing respiratory motor output via moderate hypercapnia eliminates OSA in most patients with a wider range of chemosensitivity and CO2 reserve. Reducing chemosensitivity via hyperoxia had a limited and unpredictable effect on OSA.

Acetazolamide improves loop gain but not the other physiological traits causing obstructive sleep apnoea

There is some evidence to suggest that acetazolamide may improve obstructive sleep apnoea (OSA).However, how acetazolamide affects the key traits causing OSA remains uncertain. We aimed to investigate the effect of acetazolamide on the traits contributing to OSA and its severity. Acetazolamide (500 mg twice daily) was administered for 1 week to 13 OSA subjects. Pharyngeal anatomy/collapsibility, loop gain (LG), upper-airway muscle responsiveness (gain) and the arousal threshold were determined using multiple 3 min 'CPAP pressure drops': pharyngeal anatomy/collapsibility was quantified as the ventilation at CPAP=0. LG was defined as the ratio of the ventilatory overshoot to the preceding reduction in ventilation. Upper-airway gain was taken as the ratio of the increase in ventilation to the increase in ventilatory drive across the drop. Arousal threshold was quantified as the level of ventilatory drive associated with arousal. The apnoea-hypopnoea index (AHI)was assessed on separate nights using standard polysomnography. Acetazolamide reduced the median [interquartile range] LG (3.4 [2.4-5.4] versus 2.0 [1.4-3.5]; P <0.05) and NREM AHI (50 [36-57] versus 24 [13-42] events h-1; P <0.05), but did not significantly alter pharyngeal anatomy/collapsibility, upper-airway gain, or arousal threshold. There was a modest correlation between the percentage reduction in LG and the percentage reduction in AHI (r =0.660, P =0.05). Our findings suggest that acetazolamide can improve OSA, probably due to reductions in the sensitivity of the ventilatory control system. Identification of patients who may benefit from reductions in LG alone or in combination with other therapies to alter the remaining traits may facilitate pharmacological resolution of OSA in the future.

A method for measuring and modeling the physiological traits causing obstructive sleep apnea

There is not a clinically available technique for measuring the physiological traits causing obstructive sleep apnea (OSA). Therefore, it is often difficult to determine why an individual has OSA or to what extent the various traits contribute to the development of OSA. In this study, we present a noninvasive method for measuring four important physiological traits causing OSA: 1) pharyngeal anatomy/collapsibility, 2) ventilatory control system gain (loop gain), 3) the ability of the upper airway to dilate/stiffen in response to an increase in ventilatory drive, and 4) arousal threshold. These variables are measured using a single maneuver in which continuous positive airway pressure (CPAP) is dropped from an optimum to various suboptimum pressures for 3- to 5-min intervals during sleep. Each individual's set of traits is entered into a physiological model of OSA that graphically illustrates the relative importance of each trait in that individual. Results from 14 subjects (10 with OSA) are described. Repeatability measurements from separate nights are also presented for four subjects. The measurements and model illustrate the multifactorial nature of OSA pathogenesis and how, in some individuals, small adjustments of one or another trait (which might be achievable with non-CPAP agents) could potentially treat OSA. This technique could conceivably be used clinically to define a patient's physiology and guide therapy based on the traits.

Whole genome scan for obstructive sleep apnea and obesity in African-American families

Obstructive sleep apnea (OSA) is a common, chronic disease associated with obesity. OSA and obesity are both prevalent in African Americans, who are also at increased risk for secondary complications. To identify susceptibility loci for OSA, we undertook a 9-centimorgans genome scan in 59 African-American pedigrees ascertained on the basis of either an affected individual with laboratory-confirmed disease or a proband who was a neighborhood control subject. Variance component linkage analysis was performed for the quantitative phenotypes apnea-hypopnea index (AHI) and body mass index. A candidate region on chromosome 8q (logarithm of odds [LOD] = 1.29, p = 0.006) gave the only evidence for linkage to the AHI. Body mass index was linked to multiple regions, most significantly to markers on chromosome 4q (LOD = 2.63, p = 0.0006) and 8q (LOD = 2.56, p = 0.0007). Evidence of linkage to the AHI was only slightly reduced after adjustment for body mass index. After adjustment for the AHI, some of the primary linkages to body mass index were greatly reduced whereas others remained suggestive. Our results suggest that there are both shared and unshared genetic factors underlying susceptibility to OSA and obesity, and that the genetic determinants of obesity in this population may be modulated by apnea severity.

Clinical efficacy and indication of acetazolamide treatment on sleep apnea syndrome

The efficacy and indication of acetazolamide treatment on patients with sleep apnea syndrome (SAS) were discussed from assessing the changes of polysomnographic findings with the treatment in 75 SAS patients. For the patients as a whole, respiratory disorder variables improved significantly during the treatment. However, the number of acetazolamide treatment responders who showed a decrease of apnea hypopnea index (AHI) to 50% or less of the pretreatment value numbered only 34 (45.3%). The lower values of body mass index and AHI in the responder group indicated that monotherapy with acetazolamide is the treatment choice only for mild SAS cases without obesity. However, combined treatment with acetazolamide and uvulopalatopharyngoplasty was thought to be beneficial for severe cases.