Protocol for a pragmatic trial testing a self-directed lifestyle program targeting weight loss among patients with obstructive sleep apnea (POWER Trial)

BACKGROUND

Obesity comprises the single greatest reversible risk factor for obstructive sleep apnea (OSA). Despite the potential of lifestyle-based weight loss services to improve OSA severity and symptoms, these programs have limited reach. POWER is a pragmatic trial of a remote self-directed weight loss care among patients with OSA.

METHODS

POWER randomizes 696 patients with obesity (BMI 30-45 kg/m2) and recent diagnosis or re-confirmation of OSA 1:1 to either a self-directed weight loss intervention or usual care. POWER tests whether such an intervention improves co-primary outcomes of weight and sleep-related quality of life at 12 months. Secondary outcomes include sleep symptoms, global ratings of change, and cardiovascular risk scores. Finally, consistent with a hybrid type 1 approach, the trial embeds an implementation process evaluation. We will use quantitative and qualitative methods including budget impact analyses and qualitative interviews to assess barriers to implementation.

CONCLUSIONS

The results of POWER will inform population health approaches to the delivery of weight loss care. A remote self-directed program has the potential to be disseminated widely with limited health system resources and likely low-cost.

Impact of mail-based continuous positive airway pressure initiation on treatment usage and effectiveness

PURPOSE

In-person visits with a trained therapist have been standard care for patients initiating continuous positive airway pressure (CPAP). These visits provide an opportunity for hands-on training and an in-person assessment of mask fit. However, to improve access, many health systems are shifting to remote CPAP initiation with equipment mailed to patients. While there are potential benefits of a mailed approach, relative patient outcomes are unclear. Specifically, many have concerns that a lack of in-person training may contribute to reduced CPAP adherence. To inform this knowledge gap, we aimed to compare treatment usage after in-person or mailed CPAP initiation.

METHODS

Our medical center shifted from in-person to mailed CPAP dispensation in March 2020 during the COVID-19 pandemic. We assembled a cohort of patients with newly diagnosed obstructive sleep apnea (OSA) who initiated CPAP in the months before (n = 433) and after (n = 186) this shift. We compared 90-day adherence between groups.

RESULTS

Mean nightly PAP usage was modest in both groups (in-person 145.2, mailed 140.6 min/night). We did not detect between-group differences in either unadjusted or adjusted analyses (adjusted difference - 0.2 min/night, 95% - 27.0 to + 26.5).

CONCLUSIONS

Mail-based systems of CPAP initiation may be able to improve access without reducing CPAP usage. Future work should consider the impact of mailed CPAP on patient-reported outcomes and the impact of different remote setup strategies.

Divided attention effects in visual search are caused by objects not by space

Divided attention effects have been observed across a variety of stimuli and perceptual tasks, which have given rise to both object-based and space-based theories of divided attention. Object-based theories assert that processing information from multiple objects is limited, whereas space-based theories assert that processing information from multiple locations is limited. Extant results in the literature are collectively inconsistent with both simple object-based theories and simple space-based theories of divided attention. Using a visual search task with the extended simultaneous-sequential method to reveal capacity limitations, we found evidence of limited-capacity processing of object properties and unlimited-capacity processing of feature contrast. We found no evidence of a separate spatial limitation. A multiple pathway processing theory can account for these and a large body of previous results. According to this theory, tasks that require object processing must follow a limited-capacity pathway and therefore incur divided attention effects. Tasks that depend on only feature contrast can follow a separate unlimited-capacity processing pathway and therefore do not incur divided attention effects.

Ranitidine-induced anaphylaxis: clinical features, cross-reactivity, and skin testing

BACKGROUND

Histamine H2 receptor antagonists are commonly prescribed medications and are known to be well tolerated. However, 99 cases of ranitidine-induced anaphylaxis occurred in Korea from 2007 to 2014.

OBJECTIVE

The purpose of this study was to determine the incidence, clinical features, and diagnostic methods for ranitidine-induced anaphylaxis.

METHODS

Ranitidine-related pharmacovigilance data from 2007 to 2014 were reviewed. Adverse drug reactions with causal relationships were selected, and clinical manifestations, outcomes, and drug-related information were assessed. For further investigation, 8 years of pharmacovigilance data were collected at a single centre. Twenty-three patients participated in in vivo and in vitro studies. Skin tests, oral provocation tests, and laboratory tests were performed, including tests using other kinds of histamine H2 receptor antagonists.

RESULTS

Over 7 years, 584 patients suffered adverse reactions to ranitidine. The most common manifestation was cutaneous symptoms. Among them, 99 patients (17.0%) experienced anaphylaxis. In a single-centre study, skin prick tests were positive in 91.7% of ranitidine-induced anaphylaxis patients (11/12); the optimal concentration was 20 mg/mL. Detection of ranitidine-specific immunoglobulin E failed. Cimetidine and proton pump inhibitors showed no cross-reactivity with ranitidine based on the skin prick test, oral provocation test, or clinical determination. Surprisingly, 82.6% of patients reintroduced ranitidine and re-experienced the same adverse reactions because ranitidine was not considered the culprit drug.

CONCLUSIONS AND CLINICAL RELEVANCE

Although ranitidine is known as a safe drug, it can also cause diverse adverse reactions, including anaphylaxis. This study demonstrates the need to pay attention to adverse reactions to ranitidine and consider ranitidine as a cause of anaphylaxis.

Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

The Emerging Risk Factors Collaboration: analysis of individual data on lipid, inflammatory and other markers in over 1.1 million participants in 104 prospective studies of cardiovascular diseases

Many long-term prospective studies have reported on associations of cardiovascular diseases with circulating lipid markers and/or inflammatory markers. Studies have not, however, generally been designed to provide reliable estimates under different circumstances and to correct for within-person variability. The Emerging Risk Factors Collaboration has established a central database on over 1.1 million participants from 104 prospective population-based studies, in which subsets have information on lipid and inflammatory markers, other characteristics, as well as major cardiovascular morbidity and cause-specific mortality. Information on repeat measurements on relevant characteristics has been collected in approximately 340,000 participants to enable estimation of and correction for within-person variability. Re-analysis of individual data will yield up to approximately 69,000 incident fatal or nonfatal first ever major cardiovascular outcomes recorded during about 11.7 million person years at risk. The primary analyses will involve age-specific regression models in people without known baseline cardiovascular disease in relation to fatal or nonfatal first ever coronary heart disease outcomes. This initiative will characterize more precisely and in greater detail than has previously been possible the shape and strength of the age- and sex-specific associations of several lipid and inflammatory markers with incident coronary heart disease outcomes (and, secondarily, with other incident cardiovascular outcomes) under a wide range of circumstances. It will, therefore, help to determine to what extent such associations are independent from possible confounding factors and to what extent such markers (separately and in combination) provide incremental predictive value.

Chlamydia pneumoniae and occlusive vascular disease: identification and characterization

Chlamydia pneumoniae, a respiratory pathogen, has been associated with occlusive vascular disease, including atherosclerosis and intimal hyperplasia, through seroepidemiologic studies. Furthermore, using immunohistochemistry (IHC), polymerase chain reaction (PCR), transmission electron microscopy (TEM), and in situ hybridization, this association has been reconfirmed by detecting this organism in atherosclerotic vascular tissue. This review summarizes and critically analyzes these findings and also discusses various mechanisms of how Chlamydia pneumoniae could be involved in the pathogenesis of occlusive vascular disease. Although more studies are needed to reproduce these results and, possibly, uncover a mechanism, the current literature fails to include detailed methodologies for studying Chlamydia pneumoniae. Therefore, to provide a general standard, we have also outlined specific protocols for IHC, PCR, and TEM. These protocols incorporate essential components from various studies and are presented in a concise and easily adaptable format.

Effect of water and bicarbonate loading in patients with chronic renal failure

Animal studies suggest that alkalinization and increased intake of free water both serve to decrease the rate of progression in chronic renal failure. However, clinicians have been reluctant to apply either strategy because of concerns regarding volume overload and water intoxication. We tested the effects of 2 1 daily water supplementation, with either an electrolyte-poor or a HCO3-rich (47.5 mmol/1) water in 11 patients with chronic renal failure (creatinine clearance 10 +/- 5 ml/min). The patients were brought into balance on a diet containing 80 mmol/24 h Na+, 80 mmol/24 h Cl- and 70 mmol/24 h K+. After a 3-day equilibration period, the patients were randomized to one or the other regimen for 7 days. After a 3-day washout period, the alternate regimen was given for another 7 days. Neither regimen led to weight gain or hyponatremia. The supplemental 95 mmol/24 h HCO3- lowered the serum Cl- concentration and raised the serum HCO3- concentration, as well as the pH value, to normal. Creatinine clearance and protein excretion were not affected. Serum beta 2-microglobulin concentrations decreased with the NaHCO3-containing water. Na+/H(+)-antiporter activity was not consistently influenced since an order effect of the regimens was apparent. We conclude that 2 1/24 h water and NaHCO3 supplementation is well tolerated, causes no deleterious effects, and may evoke improvement in patients with chronic renal failure.

Phospholipase D inhibitors from a Myrsine species

The phospholipase D-inhibitory activity of a methanol extract from the leaves of a New Zealand plant, Myrsine australis, has been attributed to two new saponins 1 and 2. Compound 1 was assigned as 3-0-[-beta-D-xylopyranosyl-(1-->2)-0-beta-D-glucopyranosyl-(1-->4)- -[0-beta-D -glucopyranosyl-(1-->2)]-alpha-L-arabinosyl]-16alpha-hydroxy-+ ++13beta,28-epoxyoleanane and 2 as 3beta-0-[-beta-rhamnopyranosyl-(1-->2)-0-beta-D-glucopyranosyl-(1-->4)-[ 0-beta-D-glucopranosyl]-alpha-L-arabinopyranosyl]-16alpha -hydroxy-13beta, 28-epoxyleanane. Compounds 1 and 2 showed IC50 values of 3 and 2 microM, respectively, versus phorbol 12-myrisate-13-acetate-stimulated phosphlipase D in human promyelocytic leukemic (HL-60) cells. Compounds 1 and 2 also inhibited fMLP (formyl-Met-Leu-Phe) stimulated phospholipase D with IC50 values of 8 and 24 microM, respectively.