Gary A Wittert

University of Adelaide · Discipline of Medicine

Objective We have shown that men aged 50 years+ at high risk of type 2 diabetes treated with testosterone together with a lifestyle program reduced the risk of type 2 diabetes at two years by 40% compared to a lifestyle program alone. To develop a personalized approach to treatment, we aimed to explore a prognostic model for incident type 2 diabete...

Objectives Altered sleep microarchitecture including sleep spindles and decline in cognitive function occurs with advancing age. However, the longitudinal relationship between changes in sleep neurophysiology and cognition in middle-to-late life is currently unclear. This study examined sleep micro-architecture measured by electroencephalography (E...

Introduction Obstructive sleep apnoea (OSA) and type 2 diabetes (T2D) show bidirectional relationships that negatively impact overall health. Although this relationship has been extensively studied with multiple reported OSA severity markers derived from polysomnography, no studies have systematically searched for novel OSA biomarkers of T2D. This...

Aims/hypothesis Night-shift work causes circadian misalignment and impairs glucose metabolism. We hypothesise that food intake during night shifts may contribute to this phenomenon. Methods This open-label, multi-arm, single-site, parallel-group controlled trial involved a 6 day stay at the University of South Australia’s sleep laboratory (Adelaid...

Background Indigenous populations globally have significantly high rates of type 2 diabetes compared to their non-Indigenous counterparts. This study aims to implement and evaluate the effectiveness of a culturally and contextually informed Aboriginal Diabetes Workforce Training Program on Aboriginal primary health care workforce knowledge, attitud...

Introduction Quetiapine is commonly prescribed "off-label" to people with insomnia symptoms. People with undiagnosed obstructive sleep apnea (OSA) frequently report insomnia symptoms, particularly difficulties in maintaining sleep. In 2020, 10.6 million prescriptions were dispensed for quetiapine in the United States. Yet, there is limited informat...

Background To improve diabetes management in primary health care for the Aboriginal and Torres Strait Islander peoples population, training programs that are culturally and contextually relevant to the local context are required. Using a scoping review methodology, the aim of this review was to describe the characteristics of chronic disease manage...

Study Objectives This protocol paper outlines the methods that will be used to examine the impact of altering meal timing on metabolism, cognitive performance and mood during simulated night shift. Methods Participants (male and female) will be recruited according to a-priori selected sample size to com- plete a 7-day within and between subject’s...

BACKGROUND Long occupational work hours, paid or unpaid overtime, and shift work are a common component of the labor force in high, middle, and lower-income economies globally. Bowel movement frequency and stool form in occupational settings may be important markers of stressful working conditions as well as diurnal gut microbiota action, gastroint...

Objective This review will determine whether various health interventions designed to reduce weight (lifestyle change, bariatric surgery, pharmacotherapy) in men with obesity are associated with improved fertility markers. The review will also establish whether the degree of weight loss achieved through these methods is associated with improvement....

Obstructive sleep apnea (OSA) has been linked to cancer in several clinical and community‐based cohorts. The effect in community‐based studies free of clinical referral bias needs to be replicated. In this observational prospective cohort study, we pooled data from three community‐based prospective cohorts (Uppsala Sleep and Health in Men cohort [U...

Background: e-Health refers to any health care service delivered through the internet or related technologies, to improve quality of life. Despite the increasing use of e-health interventions to manage type 2 diabetes (T2D), there is a lack of evidence about the effectiveness on diabetes distress and depression, which are common issues in those liv...

Quetiapine is an antipsychotic medication indicated for schizophrenia and bipolar disorder. However, quetiapine also has hypnotic properties and as such is increasingly being prescribed at low doses ‘off‐label’ in people with insomnia symptoms. Pharmacologically, in addition to its dopaminergic properties, quetiapine also modulates multiple other t...

While psychotherapeutic e-mental health interventions may circumvent barriers that many men face in accessing mental health care, the effects of men using these interventions have not been evaluated. We aimed to synthesise the characteristics of psychotherapeutic e-mental health interventions for depression or anxiety that have been trialled and ev...

Introduction: Osteoporosis prevalence will increase in coming decades, with significant financial and economic implications. Whilst alcohol excess has significant detrimental impacts on bone mineral density (BMD), knowledge of low-volume consumption is inconsistent. Type of alcohol may mediate impact on BMD and warrants further investigation. Mat...

Objective: To determine if testosterone treatment effect on glycaemia is mediated through changes in total fat mass, abdominal fat mass, skeletal muscle mass, non-dominant handgrip, oestradiol (E2), and sex hormone-binding globulin (SHBG). Design: Mediation analysis of a randomised placebo-controlled trial of testosterone. Methods: Six Austral...

Purpose Prospective studies examining associations between baseline sleep microarchitecture and future cognitive function recruited from small samples with predominantly short follow-up. This study examined sleep microarchitecture predictors of cognitive function (visual attention, processing speed, and executive function) after 8 years in communit...

Objectives: Previous studies examining associations between sleep spindles and cognitive function attempted to account for obstructive sleep apnea (OSA) without consideration for potential moderating effects. To elucidate associations between sleep spindles, cognitive function, and OSA, this study of community-dwelling men examined cross-sectional...

Study objectives Prospective studies examining associations of obstructive sleep apnea (OSA) and sleep macroarchitecture with future cognitive function remain limited to older participants, many with baseline cognitive impairment, which may be a confounder. This study examined OSA and sleep macroarchitecture predictors of cognitive function (visual...

Study objectives Prospective studies examining associations of sleep microarchitecture with future cognitive function predominantly recruited from small samples with relatively short follow-up. Therefore, this study examined sleep microarchitecture predictors of cognitive function (visual attention, processing speed, and executive function) after 8...

Introduction Cortisol regulates multiple body systems and displays a distinct circadian rhythm. Nightshift disrupts this rhythm likely disturbing physiological processes regulated by cortisol. The cumulative effect of consecutive nightshifts, and eating during nightshift, on cortisol is unclear. This study aimed to determine the impact of four-cons...

BACKGROUND Only a minority of adult males who experience depression or anxiety receive any formal help from a healthcare professional for these issues. While psychotherapeutic e-mental health interventions may circumvent or reduce many of the barriers males face when accessing mental health care, the effects of these interventions in male populatio...

Study Objectives To determine if a novel EEG-derived continuous index of sleep depth/alertness, the odds ratio product (ORP), predicts self-reported daytime sleepiness and poor sleep quality in two large population-based cohorts. Methods ORP values which range from 0 (deep sleep) to 2.5 (fully alert) were calculated in 3s intervals during awake pe...

Aims Very low-carbohydrate (LC) diets are popular for type 2 diabetes (T2DM) management; however, long-term effects on psychological health remain largely unknown. This study reports the effects of a LC diet on mood and cognitive function after 2 years and explores the potential predictors of changes in psychological health. Methods 115 adults (57...

Preliminary research has shown the effectiveness of supervised exercise-based interventions in alleviating sequela resulting from metastatic prostate cancer. However, many individuals encounter barriers that limit the uptake of face-to-face exercise. Technology-enabled interventions offer a distance-based alternative. This pilot study aimed to expl...

Introduction: Sleep microarchitecture metrics determined by quantitative power spectral analysis (PSA) of the electroencephalogram (EEG) have been proposed as potential biomarkers of cognitive function. However, there remain no data from community-based samples. This study examined cross-sectional associations between sleep microarchitecture metric...

Introduction: The association between sleep spindles and cognitive function and the potential confounding influence of obstructive sleep apnea (OSA) remains uncertain. This study examined cross-sectional associations between sleep spindle metrics and cognitive function outcomes in community-dwelling men. Methods: Men, Androgen, Inflammation, Lifes...

Eating architecture is a term that describes meal frequency, meal timing, and meal size and the daily variation in each of these. The aim of this study was to determine the relationship between components of eating architecture on body fat and markers of glycaemic control in healthy adults at increased risk of type 2 diabetes (T2DM). Participants (...

‘Pathological hypogonadism’, reflecting disease within the hypothalamo–pituitary–testicular (HPT) axis occurs in under 2.5% of men. However, low serum testosterone (T) concentrations, which affect up to 40% of middle-aged and elderly men in some populations, are more frequently attributable to acute and chronic disease, medication use, and lifestyl...

Introduction Sleep spindles are thought to play an important role in learning and memory. The association between sleep spindles and cognitive function and the potential confounding influence of obstructive sleep apnea (OSA) is uncertain. We examined the cross-sectional association between sleep spindles and cognitive function controlled for OSA in...

Objective: To examine prostate cancer (PCa) survivors' sexual help-seeking intentions, behaviours, and unmet needs. Methods: In this prospective cohort study, men who underwent active, non-hormonal treatment completed baseline (N = 558) and 6-month follow-up (N = 387) questionnaires. Theory of planned behaviour (TPB) constructs (sexual help-seek...

BACKGROUND Digital health interventions such as tailored websites are emerging as valuable tools to provide individualised exercise and behavioural change information for individuals diagnosed with cancer. OBJECTIVE The purpose of this research was to investigate and iteratively refine the acceptability and usability of a web-based exercise interv...

Background Digital health interventions such as tailored websites are emerging as valuable tools to provide individualized exercise and behavioral change information for individuals diagnosed with cancer. Objective The aim of this study is to investigate and iteratively refine the acceptability and usability of a web-based exercise intervention (E...

Background Moderate to vigorous physical activity (MVPA) interventions reduce the severity of obstructive sleep apnoea, however, little epidemiological research exists to confirm these findings. Methods 789 participants from the population-based Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) Study underwent polysomnography. MV...

Introduction Preliminary research has shown the effectiveness of supervised exercise-based interventions in alleviating sequela resulting from metastatic prostate cancer. Despite this, many individuals do not engage in sufficient exercise to gain the benefits. There are many barriers, which limit the uptake of face-to-face exercise in this populati...

Background Men who are overweight or obese frequently have low serum testosterone concentrations, which are associated with increased risk of type 2 diabetes. We aimed to determine whether testosterone treatment prevents progression to or reverses early type 2 diabetes, beyond the effects of a community-based lifestyle programme. Methods T4DM was...

Despite abundant cross-sectional evidence that low vitamin D status is associated with risk of cognitive decline in ageing, interventional evidence for benefits of vitamin D supplementation is lacking. This study was a 6 month randomised, double-blinded placebo-controlled clinical trial of the effects of vitamin D3 (D3), enhanced vitamin D2 in a mu...

Objective The commute home following a night shift is associated with an increased risk for accidents. This study investigated the relationship between food intake during the night shift and simulated driving performance post-shift. Methods Healthy non-shift working males (N=23) and females (N=16), aged 18–39 years (mean 24.5, standard deviation 5...

Purpose Reduced hand grip strength (HGS) is associated with poorer health in chronic conditions, yet there has been little research examining the association with hand grip strength and obstructive sleep apnea (OSA). Further, these studies have not examined, nor adjusted, for muscle mass. The aim of this study was to determine associations between...

Background: Web-based computer-tailored interventions can assist prostate cancer survivors to become more physically active by providing personally relevant behaviour change support. This study aimed to explore how changing the website architecture (free choice vs. tunnelled) impacted engagement within a physical activity computer-tailored interve...

Background: Few individuals with metastatic prostate cancer have access to prostate cancer-specific exercise support, despite demonstrated benefits. eHealth tools, such as websites, may be viable options for increasing access. To be effective and acceptable, future eHealth websites need to consider end-users' perspectives, capacity and needs. We a...

Background: Colorectal cancer (CRC) is rising in incidence in young adults, and this observation is currently unexplained. We investigated whether having a personal history of type 2 diabetes mellitus (T2D) was a potential risk factor for young‐onset colorectal cancer (YOCRC). Methods: The South Australian Young Onset (SAYO) CRC study is a series o...

Aim This review aimed to assess the effectiveness of multifaceted in-hospital interventions for patients with type 2 diabetes mellitus on hospital readmission, hospital length of stay (LOS), and glycated haemoglobin (HbA1c). Methods The search included MEDLINE, EMBASE, Emcare, Web of Science, PsycINFO and Google Scholar from 2007 to current date a...

Introduction: Preliminary research has shown the effectiveness of supervised exercise-based interventions in alleviating sequela resulting from metastatic prostate cancer. Despite this, many individuals do not engage in sufficient exercise to gain the benefits. There are many barriers which limit the uptake of face-to-face exercise in this populati...

Introduction: Preliminary research has shown the effectiveness of supervised exercise-based interventions in alleviating sequela resulting from metastatic prostate cancer. Despite this, many individuals do not engage in sufficient exercise to gain the benefits. There are many barriers which limit the uptake of face-to-face exercise in this populati...

Background: Effects of very low carbohydrate (VLC) diets on appetite response in individuals with type 2 diabetes remain unclear. Objective: A secondary analysis was conducted to determine appetite responses to an energy-restricted [30% of energy (%E) deficit] very low carbohydrate (VLC) diet compared with a higher carbohydrate (HC) diet in adul...

Altering meal timing could improve cognition, alertness, and thus safety during the nightshift. This study investigated the differential impact of consuming a meal, snack, or not eating during the nightshift on cognitive performance (ANZCTR12615001107516). 39 healthy participants (59% male, age mean±SD: 24.5 ± 5.0y) completed a 7-day laboratory stu...

Background/aims: Participant recruitment to diabetes prevention randomised controlled trials is challenging and expensive. The T4DM study, a multicentre, Australia-based, Phase IIIb randomised controlled trial of testosterone to prevent Type 2 diabetes in men aged 50-74 years, faced the challenge of screening a large number of prospective particip...

The aim of this study was to determine whether testicular volume is correlated with clinical and biochemical markers of hypothalamic-pituitary-testicular (HPT) axis function. This was a cross-sectional substudy of a larger randomized controlled trial including obese men, body mass index (BMI) ≥30 kg m-2, with a total testosterone level <12 nmol l-1...

Introduction: Emerging evidence suggests us of real-time continuous glucose monitoring systems (RT-CGM), can assist to improve glucose control in Type 2 Diabetes (T2D) treatment, however the impact of these devices on patients' stress levels and behaviour is poorly understood. This study aimed to examine the effects of RT-CGM on tolerance and acce...

The Masculinity in Chronic Disease Inventory (MCD-I) is a new measure of internalized masculine beliefs previously validated in the context of prostate cancer. The present study assessed the validity of the MCD-I in men with other chronic diseases to explore its potential for wider application. A cross-sectional survey of 633 men aged 47–93 years o...

Background: Effective interventions are required to prevent the current rapid increase in the prevalence of Type 2 diabetes. Clinical trials of large-scale interventions to prevent Type 2 diabetes are essential but recruitment is challenging and expensive, and there are limited data regarding the most cost-effective and efficient approaches to rec...

Shiftworkers report eating during the night when the body is primed to sleep. This study investigated the impact of altering food timing on subjective responses. Healthy participants (n = 44, 26 male, age Mean ± SD = 25.0 ± 2.9 years, BMI = 23.82 ± 2.59kg/m2) participated in a 7-day simulated shiftwork protocol. Participants were randomly allocated...

Objective: Contrasting findings exist regarding the associations between circulating sex hormone-binding globulin (SHBG) and total testosterone (TT) with type 2 diabetes (T2D) and cardiovascular diseases (CVD) in men. We examined prospective associations of SHBG and TT with incident T2D and CVD, in a cohort of community-dwelling men. Methods: Parti...

Objectives To identify and review evaluations of strategies to recruit men aged 50 years and over to randomised controlled trials (RCTs). Design Systematic review and narrative synthesis. Data sources MEDLINE, EMBASE, CINAHL and ORRCA databases were searched to 1 December 2017. Eligibility criteria Studies using quantitative methods to evaluate...

Objectives: The aim of the study was to compare the response rates and costs of phone call vs. short message service (SMS) screening reminders to prospective randomized controlled trial (RCT) participants. Study design and setting: This study was a randomized evaluation within a large Australian diabetes prevention RCT. Participants were men age...

Objective: The objective of this review is to examine the association between serum testosterone concentration and the presence and severity of depression in men. Introduction: Cross-sectional and longitudinal cohort studies examining the relationship between serum testosterone concentration and depression in men have produced mixed results. The...

Introduction Optimising patient adherence to prescribed lifestyle interventions to achieve improved blood glucose control remains a challenge. Combined use of real-time continuous glucose monitoring systems (RT-CGM) may promote improved glycaemic control. This pilot study examines the effects of a prescriptive lifestyle modification programme when...

Background Aboriginal and Torres Strait Islander men have the highest morbidity and mortality rates, and lowest rates of health service utilization in Australia. There is a current perception that Aboriginal and Torres Strait Islander men are disinterested in their health. This study aimed to identify the perceived motivators, barriers and enablers...

Background Low circulating testosterone is associated with an increased risk of developing type 2 diabetes (T2DM) in overweight men with impaired glucose tolerance (IGT). Aim To determine in a multi‐centre, double‐blinded placebo‐controlled randomised trial, whether testosterone treatment combined with lifestyle intervention (Weight Watchers®) rel...

Multiple inputs, including consumer engagement, is considered best practice for person centred designs for digital intervention design. However, juggling the needs of many stakeholders can be tricky. The tone, content, and capacity to tailor messages have to be balanced between the expert and the needs of the user. All parties agreed that video tut...

Previous studies have shown that people with schizophrenia have high rates of Obstructive Sleep Apnoea (OSA). Despite this, intervention studies to treat OSA in this population have not been undertaken. The ASSET (Assessing Sleep in Schizophrenia and Evaluating Treatment) pilot study investigated Continuous Positive Airway Pressure (CPAP) treatment...

Background Aboriginal and Torres Strait Islander men experience worse health outcomes and are the most marginalized and disadvantaged population group in Australia. Primary health care services are critical to providing both clinical and social and emotional support, however, remain underutilized by Aboriginal and Torres Strait Islander men. This r...

Background There is a direct relationship between bodyweight and risk of diabetes. Lorcaserin, a selective serotonin 2C receptor agonist that suppresses appetite, has been shown to facilitate sustained weight loss in obese or overweight patients. We aimed to evaluate the long-term effects of lorcaserin on diabetes prevention and remission. Methods...

Context In men, circulating 17β-estradiol originates primarily from peripheral aromatization of testosterone particularly in adipose tissue. The effect of ageing and obesity on circulating estradiol remains unclear. Objective Determine five-year changes in serum estradiol and the association with testosterone and fat mass in Australian men. Desig...