Diurnal changes in central blood pressure and pulse pressure amplification in patients with obstructive sleep apnoea

The influence of body composition and fat distribution on circadian blood pressure rhythm and nocturnal mean arterial pressure dipping in patients with obesity

Loss of physiological nocturnal blood pressure (BP) decline is an independent predictor of cardiovascular risk and mortality. The aim of the study was to investigate the influence of body composition and fat distribution on 24-hour BP pattern and nocturnal dipping of mean arterial pressure (MAP) in patients with obesity. The study comprised 436 patients, 18 to 65 years old (306 women), with BMI ≥30 kg/m2. Body composition was assessed with dual-energy X-ray absorptiometry (DXA) and blood pressure was assessed by 24-hour BP monitoring. The prevalence of hypertension was 64.5% in patients with BMI <40 kg/m2 and increased to 78.7% in individuals with BMI ≥50 kg/m2 (p = 0.034). The whole-body DXA scans showed that the hypertensive patients were characterized by a greater lean body mass (LBM) and a higher abdominal-fat-to-total-fat-mass ratio (AbdF/FM), while the normotensive participants had greater fat mass, higher body fat percentage and more peripheral fat. Loss of physiological nocturnal MAP decline was diagnosed in 50.2% of the patients. The percentage of non-dippers increased significantly: from 38.2% in patients with BMI <40 kg/m2 to 50.3% in those with BMI 40.0-44.9 kg/m2, 59.0% in patients with BMI 45.0-49.9 kg/m2, 71.4% in those with BMI 50.0-54.9 kg/m2 and 83.3% in patients with BMI ≥55 kg/m2 (p = 0.032, p = 0.003, p<0.001, and p = 0.002 vs. BMI <40 kg/m2, respectively). The multivariable regression analysis showed that patients at the highest quartiles of body weight, BMI, LBM and AbdF/FM had significantly reduced nocturnal MAP dipping compared with patients at the lowest quartiles, respectively.

Feasibility of 3-month melatonin supplementation for brain oxidative stress and sleep in mild cognitive impairment: protocol for a randomised, placebo-controlled study

INTRODUCTION

Melatonin has multiple proposed therapeutic benefits including antioxidant properties, synchronisation of the circadian system and lowering of blood pressure. In this protocol, we outline a randomised controlled trial to assess the feasibility, acceptability and tolerability of higher dose (25 mg) melatonin to target brain oxidative stress and sleep disturbance in older adults with mild cognitive impairment (MCI).

METHODS AND ANALYSIS

The study design is a randomised double-blind, placebo-controlled, parallel group trial. Forty individuals with MCI will be recruited from the Healthy Brain Ageing Clinic, University of Sydney and from the community, and randomised to receive either 25 mg oral melatonin or placebo nightly for 12 weeks. The primary outcomes are feasibility of recruitment, acceptability of intervention and adherence to trial medication at 12 weeks. Secondary outcomes will include the effect of melatonin on brain oxidative stress as measured by magnetic resonance spectroscopy, blood pressure, blood biomarkers, mood, cognition and sleep. Outcomes will be collected at 6 and 12 weeks. The results of this feasibility trial will inform a future conclusive randomised controlled trial to specifically test the efficacy of melatonin on modifiable risk factors of dementia, as well as cognition and brain function. This will be the first trial to investigate the effect of melatonin in the population with MCI in this way, with the future aim of using this approach to reduce progression to dementia.

ETHICS AND DISSEMINATION

This protocol has been approved by the Sydney Local Health District Ethics Committee (X18-0077). This randomised controlled trial will be conducted in compliance with the protocol published in the registry, the International Conference for Harmonisation on Good Clinical Practice and all other applicable regulatory requirements. The findings of the trial will be disseminated via conferences, publications and media, as applicable. Participants will be informed of results of the study at the conclusion of the trial. Eligible authors will include investigators who are involved in the conception and design of the study, the conduct of the trial, the analysis of the results, and reporting and presentation of study findings.

TRIAL REGISTRATION NUMBER

Australian and New Zealand Clinical Trials Registry (ANZCTRN 12619000876190).

PROTOCOL VERSION

V.8 15 October 2020.