Daniel Gagnon

Daniel Gagnon
Montreal Heart Institute · Research Centre

PhD

About

188
Publications
19,715
Reads
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2,912
Citations
Introduction
My research activities are composed of two complementary themes. The first examines the integrated physiological responses to thermal stress in humans and how they are affected by sex, age, and disease. The second examines the potential benefits of heat exposure for the primary and secondary prevention of cardiovascular diseases.
Additional affiliations
October 2013 - April 2016
University of Texas Southwestern Medical Center
Position
  • PostDoc Position
September 2008 - October 2012
University of Ottawa
Position
  • PhD Student

Publications

Publications (188)
Article
Full-text available
Key points With the advent of more frequent extreme heat events, adaptability to hot environments will be crucial for the survival of many species, including humans. However, the mechanisms that mediate human heat adaptation have remained elusive. We tested the hypothesis that heat acclimation improves the neural control of body temperature. Skin s...
Article
As global temperatures continue to rise, extreme heat events are becoming more frequent and intense. Extreme heat affects cardiovascular health as it is associated with a greater risk of adverse cardiovascular events, especially for adults with preexisting cardiovascular diseases. Nonetheless, the pathophysiology underlying the association between...
Article
The human body constantly exchanges heat with the environment. Temperature regulation is a homeostatic feedback control system that ensures deep body temperature is maintained within narrow limits despite wide variations in environmental conditions and activity-related elevations in metabolic heat production. Extensive research has been performed t...
Article
The world is warming at an unprecedent rate and our future will be defined by hotter weather and its associated health risks. Hot weather reduces the likelihood of engaging in outdoor physical activity and increases the risk of heat-related illnesses. Promoting safe physical activity in a warmer climate is especially important for adults with cardi...
Article
Background: Heat extremes are associated with greater risk for cardiovascular death. The pathophysiologic mechanisms mediating this association are unknown. Objective: To quantify the myocardial blood flow (MBF) requirements of heat exposure. Design: Experimental study. (ClinicalTrials.gov: NCT04549974). Setting: Laboratory-based. Participa...
Article
The use of better normalized cardiorespiratory fitness (VO2max) metrics (predicted value (VO2/pred) or lean mass (VO2/LM)) could improve our understanding of the relationship between VO2max and cognition in older adults with cardiovascular risk factors (CVRFs). PURPOSE: Determine the associations between two normalized VO2max metrics (VO2/pred and...
Article
Full-text available
The compensatory reserve index (CRI), derived from machine learning algorithms from peripherally obtained photoplethysmography signals, provides a non‐invasive assessment of cardiovascular stability, that may be useful clinically. Briefly, the CRI device provides a value between 0 and 1, with 1 reflecting full compensable capabilities and 0 reflect...
Article
Full-text available
Background Studies on the associations between cardiorespiratory fitness (VO2max) and cognition have used inconsistent methods, which could explain the variability in the results. Understanding how ventilatory, cardiac and peripheral determinants of VO2max impact cognition would allow us to better prevent cognitive decline. Purpose Determine the r...
Article
Background Cardiac rehabilitation programs provide a valuable opportunity to promote the adoption of healthy lifestyle behaviors in patients with atherosclerotic cardiovascular diseases (ASCVD) and metabolic comorbidities, including metabolic syndrome (MetS) and prediabetes. However, strategies to reverse these conditions remain to be explored. Ob...
Conference Paper
Introduction: Heat extremes are associated with a greater risk of adverse cardiovascular outcomes, especially among adults with coronary artery disease. While air-conditioning provides exceptional protection during heat extremes, it is neither sustainable nor widely accessible. Cold-water foot immersion reduces physiological heat strain in healthy...
Conference Paper
Introduction: Extreme heat events (EHE) continue to increase in frequency, intensity, and duration, posing a significant health threat to vulnerable populations. Despite the development of heat-health action plans, heat-related injuries during EHE persist with the majority occurring at-home. Although epidemiological evidence has identified vulnerab...
Article
Full-text available
INTRODUCTION. To thrive in a warmer climate, humans will need to adapt physiologically. Improved thermoregulatory and cardiovascular responses during heat acclimation have been widely described. However, the cellular and molecular mechanisms mediating these improvements remain understudied in humans. The aim of this study was to perform a broad-spe...
Conference Paper
INTRODUCTION: Extreme heat events are associated with a greater risk of cardiovascular mortality, especially in adults with pre-existing heart disease. The pathophysiological mechanisms mediating these relationships remain unknown. One proposed mechanism, supported by pre-clinical studies employing heat stroke models of severe body hyperthermia, is...
Article
Background: Several studies indicate that various heat exposure interventions improve peripheral endothelial function and microvascular reactivity, as well as reduce central arterial stiffness and blood pressure in various populations. Nonetheless, few studies have considered the potential therapeutic effects of heat exposure for people living with...
Article
Introduction: Aerobic exercise interventions improve peripheral endothelial function in healthy older males. However, this effect is not always observed in healthy postmenopausal females and possible mechanisms underlying this sex-related difference remain unknown. Greater vascular shear stress during acute exercise is a key stimulus mediating long...
Article
Context: Aging is accompanied by a reduced capacity to dissipate heat. Heat acclimation has been shown to improve heat loss capacity in young healthy adults, yet few studies have investigated the capacity of older adults to adapt to repeated bouts of heat exposure, particularly when using a passive heat acclimation protocol. Furthermore, it remains...
Conference Paper
Full-text available
Context: Aging is accompanied by a reduced capacity to dissipate heat. Heat acclimation has been shown to improve heat loss capacity in young healthy adults, yet few studies have investigated the capacity of older adults to adapt to repeated bouts of heat exposure, particularly when using a passive heat acclimation protocol. Furthermore, it remains...
Article
Full-text available
Background: To limit exposures to occupational heat stress, leading occupational health and safety organizations recommend work–rest regimens to prevent core temperature from exceeding 38°C or increasing by ≥1°C. This scoping review aims to map existing knowledge of the effects of work–rest regimens in hot environments and to propose recommendation...
Article
The world is experiencing increased frequency, duration, and severity of life-threatening heat extremes. Most hospitalizations and excess deaths during extreme heat events are associated with pre-existing diseases in older adults. As climate change persists, the global population ages, and the number of individuals with chronic diseases expands, mo...
Article
Full-text available
Hotter climates have important impacts on human health and performance. Yet, the cellular and molecular responses involved in human heat stress and acclimation remain understudied. This dataset includes physiological measurements and the plasma concentration of 2,938 proteins collected from 10 healthy adults, before and during passive heat stress t...
Poster
BACKGROUND: The clinical care of adults with a systemic right ventricle with biventricular circulation (sRV-biV) is influenced by cardiorespiratory fitness (CRF) evaluation. However, prognostic markers for CRF are derived from analyses of adults with a systemic left ventricle (sLV). While some studies suggest that CRF is lower in adults with sRV-bi...
Article
Background: The clinical care of adults with a systemic right ventricle with biventricular circulation (sRV-biV) is influenced by cardiorespiratory fitness (CRF) evaluation. However, prognostic markers for CRF are derived from analyses of adults with a systemic left ventricle (sLV). While some studies suggest that CRF is lower in adults with sRV-bi...
Poster
Full-text available
BACKGROUND: Exercise training (ET) at home can be a good alternative to encourage access and participation to primaryprevention programs in older adults with cardiovascular risk factors (CVRF). ET can improve prognosis, cardiopulmonary, hemodynamic functions, and quality of life of older adults with CVRF. Maximal oxygen uptake (VO2max) is a powerfu...
Poster
BACKGROUND: Cognitive impairment affects up to 50% of patients with heart failure (HF) and is associated with high mortality rates, poor quality of life and reduced functional capacities. There appears to be a bi-directional relationship between HF and cognitive impairment: HF induces cognitive impairment, which can lead to suboptimal treatment adh...
Poster
BACKGROUND: The clinical care of adults with a systemic right ventricle with biventricular circulation (sRV-biV) is, in part, guided by cardiorespiratory fitness (CRF) evaluation. A problem lies in the fact that prognosis is informed by values derived from adults with a systemic left ventricle (sLV). Some studies show that CRF is lower in adults wi...
Article
Full-text available
Planet Earth is warming at an unprecedented rate and our future is now assured to be shaped by the consequences of more frequent hot days and extreme heat. Humans will need to adapt both behaviorally and physiologically to thrive in a hotter climate. From a physiological perspective, countless studies have shown that human heat acclimation increase...
Article
Full-text available
Introduction: Despite proven programmes, implementing lifestyle interventions for pre-diabetes and type 2 diabetes is challenging. Cardiac rehabilitation, provide a valuable opportunity to promote the adoption of healthy lifestyle behaviours for patients with atherosclerotic cardiovascular disease (ASCVD). However, only a limited number of studies...
Article
Aims: Regular Finnish sauna use is associated with a reduced risk of cardiovascular mortality. However, physiological mechanisms underlying this association remain unknown. This study determined if an 8-week Finnish sauna intervention improves peripheral endothelial function, microvascular function, central arterial stiffness, and blood pressure i...
Article
BACKGROUND: Regular Finnish sauna use has been associated with a reduced risk of cardiovascular mortality. However, physiological mechanisms underlying this association remain unknown. Other forms of heat therapy have been shown to improve markers of vascular health in healthy young adults, middle-aged adults with cardiovascular risk factors, and o...
Article
INTRODUCTION. Extreme heat is associated with a greater risk of cardiovascular mortality in older adults. However, the pathophysiology that links extreme heat and cardiovascular mortality remains unknown. One possibility is that myocardial oxygen requirements during heat exposure surpass the capacity for myocardial oxygen delivery, thereby predispo...
Article
Introduction: The prevalence of hypertension is greater in post-menopausal females compared to males of similar age. Previous meta-analyses of normotensive and hypertensive adults have shown that aerobic exercise training reduces systolic (SBP) and/or diastolic (DBP) blood pressure. However, the effect of aerobic exercise training on blood pressur...
Article
Full-text available
This retrospective exploratory analysis aimed to improve our understanding of the effect of passive heat stress and subsequent heat acclimation on the circulating concentration of extracellular vesicles (EVs). Healthy young adults (four females and six males, 25 ± 4 years of age, 1.72 ± 0.08 m in height and weighing 71.6 ± 9.0 kg) were heated with...
Article
Purpose: This study tested the hypothesis that the combination of cold temperature and wind further reduces time to ischemia during treadmill stress testing compared to cold temperature alone. Methods: Eighteen participants (56 ± 9 years) with stable angina performed 4 treadmill stress tests in a randomized crossover design at +20 °C and -8 °C,...
Article
Full-text available
The aim of this study was to gain a better understanding of the acute effect of heat exposure on brachial artery flow‐mediated dilatation (FMD) and postocclusion reactive hyperaemia (PORH) by: characterizing the time course of changes post‐heating; comparing forearm and whole‐body heating; determining the impact of forearm heating during whole‐body...
Article
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The primary aim of this investigation was to determine the individual contribution of the cutaneous and skeletal muscle circulations to the cold‐induced pressor response. To address this, we examined local vascular resistances in the cutaneous and skeletal muscle of the arm and leg. Thirty‐four healthy individuals underwent three different protocol...
Article
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Menopause accelerates increases in arterial stiffness and decreases cognitive performances. The objective of this study was to compare cognitive performances in physically active pre- and post-menopausal females and their relationship with arterial stiffness. We performed a cross-sectional comparison of blood pressure, carotid–femoral pulse wave ve...
Article
Introduction: Extreme heat is associated with a greater risk of cardiovascular mortality in older adults (≥60 years). However, the pathophysiology that links extreme heat and cardiovascular mortality remains unknown. One possibility is that myocardial oxygen requirements during heat exposure cannot be met by sufficient increased in myocardial bloo...
Article
Background: Post-menopausal females appear resistant to the beneficial effects of exercise on endothelial function. Repeated increases in shear stress are considered important mediators of exercise-induced improvements in endothelial function. It is therefore possible that endothelial sensitivity to shear stress is reduced in post-menopausal femal...
Article
Introduction: Extreme heat is associated with a greater risk of mortality that particularly affects older adults with cardiovascular disease (CVD). Regular heat exposure induces an adaptation of thermoregulatory mechanisms (acclimation) that may alleviate thermal and/or cardiac strain during subsequent heat exposure. However, limited research has...
Article
Introduction: Extreme heat is associated with a greater risk of adverse cardiovascular events, especially in people with cardiovascular disease. Many patients with cardiovascular disease are prescribed beta-blockers. Some research suggests that in young healthy adults, cardio-selective beta-blockers may alter heat loss capacity. However, the effec...
Article
Aim: Heat therapy is a promising strategy to improve cardiometabolic health. This study evaluated the acute physiological responses to hot water immersion in adults with type 2 diabetes mellitus (T2DM). Methods: On separate days in randomized order, 13 adults with T2DM (8 males/5 females, 62 ± 12 yrs, BMI: 30.1 ± 4.6 kg/m2) were immersed in ther...
Article
Purpose: The benefits of exercise on vascular health are inconsistent in postmenopausal females. We investigated if blood pressure and markers of vascular function differ between physically active early post- and late premenopausal females. Methods: We performed a cross-sectional comparison of 24-h blood pressure, brachial artery flow-mediated d...
Article
Full-text available
This study evaluated if passive controlled hyperthermia heat acclimation modulates cognitive performance during passive heat stress. Eight healthy adults (25 ± 4 years) underwent 7 consecutive days of hot water immersion (core temperature ≥38.6 °C) and a 7-day time-control period. On days 1 and 7 of heat acclimation, participants performed a digita...
Article
Human thermoregulatory control is often evaluated through the relationship between thermoeffector output and core or mean body temperature. In addition to providing a general indication of whether a variable of interest alters thermoregulatory control, this relationship is often used to determine how this alteration may occur. This latter interpret...
Article
Full-text available
Background While the number of people with hypertension (HBP) continues to increase, the therapeutic target for optimal blood pressure (BP) has been revised to a lower level. Studies have suggested that High-Intensity Interval Training (HIIT) could be as efficient as BP-lowering drugs, but no study has compared their efficacy in a randomized trial....
Article
It is generally accepted that older adults display an impaired cardiovascular response to heat stress, and it has been suggested that this impaired response contributes to their increased risk of mortality during extreme heat events. Seminal studies have shown that cutaneous vasodilation, the redistribution of blood flow from visceral organs and th...
Article
We examined if the change in heart rate variability during passive heat exposure is modified by hot water heat acclimation (HA). Sixteen healthy adults (28 ± 5 years, 5 females/11 males) underwent heat exposure in a water-perfused suit, before and after 7 days of HA (60 min at rectal temperature ≥38.6 °C). During passive heat exposure, heart rate,...
Article
A lower heart rate (HR) during heat exposure is a classic marker of heat acclimation (HA), although it remains unclear whether this adaptation occurs secondary to reduced thermal strain and/or improvements in cardiac function. We evaluated the hypothesis that short-term passive HA reduces HR and improves cardiac function during passive heating. Ech...
Article
New findings: What is the central question of this study? Does passive heat acclimation alter glomerular filtration rate and urine concentrating ability in response to passive heat stress? What is the main finding and its importance? Glomerular filtration rate remained unchanged following passive heat stress, and heat acclimation did not alter thi...
Article
Objectives Finnish sauna bathing is associated with a reduced risk of adverse health outcomes. The acute physiological responses elicited by Finnish sauna bathing that could explain this association remain understudied. This study characterized the acute effect of Finnish sauna bathing on circulating markers of inflammation in healthy middle-aged a...
Article
Background Finnish sauna bathing habits are associated with a decreased risk of cardiovascular mortality. The physiological adaptations mediating this association remain to be fully elucidated. This study tested the hypothesis that Finnish sauna bathing acutely improves peripheral flow-mediated dilation (FMD) in middle-aged and older adults with st...
Article
New findings: What is the topic of this review? The aim is to examine the influence of hypoxia on thermoregulatory and cardiovascular control in the cold. What advances does it highlight? Exposure to hypoxia seems to alter both thermoregulatory and cardiovascular control, but these conclusions are based on limited data and this review highlights t...
Poster
Introduction Insulin resistance and hyperglycemia predispose individuals with type 2 diabetes mellitus (T2DM) to endothelial dysfunction and a greater risk of cardiovascular diseases. Numerous animal studies suggest that heat exposure improves glucose control and human studies suggest that it improves markers of vascular health. However, the physio...
Poster
INTRODUCTION Hyperthermia affects cognitive performance, particularly decision‐making, the speed of performing a task and the ability to perform complex tasks. Cognitive performance is generally thought to be impaired by hyperthermia, although a u‐shaped relationship may exist between the level of hyperthermia and cognitive performance. Few studies...
Poster
INTRODUCTION Heat acclimation attenuates the increase in heart rate during heat exposure. This heat acclimation‐induced bradycardia has been associated with increased stroke volume due to blood volume expansion. However, exercise‐induced heat acclimation also modulates cardiac parasympathetic activity, as measured through heart rate variability (HR...
Article
New findings: What is the central question of this study? Are fitness-related improvements in thermoregulatory responses during uncompensable heat stress mediated by aerobic capacity (VO2max ) or is it the partial acclimation associated with training? What is the main finding and its importance? During uncompensable heat stress, individuals with h...
Article
Full-text available
Background The intensity of inflammatory response triggered by cardiopulmonary bypass (CPB) during cardiac surgery has been associated with adverse outcomes. Neutrophils might contribute to organ injury through the liberation of DNA histone-based structures named “neutrophil extracellular traps” (NETs). Our objective was to assess circulating NETs...
Article
During heat stress, the skin vasculature can greatly increase conductance secondary to vasodilation. The subsequent increase in skin blood flow allows for convective heat transfer from the core to the skin and between the skin surface and the surrounding environment. Measuring skin blood flow, therefore, provides valuable information regarding heat...
Article
Full-text available
Regular Finnish sauna bathing is associated with a reduced risk of all-cause and cardiovascular mortality in middle-aged and older adults. Potential acute physiological adaptations induced by sauna bathing that underlie this relationship remain to be fully elucidated. The purpose of this study was to determine if typical Finnish sauna sessions acut...
Article
Background Frequent Finnish sauna bathing is associated with a decreased risk of cardiovascular mortality in middle‐aged men, including men with pre‐existing cardiovascular diseases. However, the potential physiological adaptations that mediate the protective effect of Finnish sauna bathing remain to be determined. In healthy young and older adults...
Article
Cardiovascular diseases (CVD) are highly prevalent in spinal cord injury (SCI), and peripheral vascular dysfunction might be a contributing factor. Recent evidence demonstrates that exposure to heat stress can improve vascular function and reduce the risk of CVD in uninjured populations. We therefore aimed to examine the extent of vascular dysfunct...
Article
Skeletal muscle blood flow is attenuated in aged humans performing aerobic exercise, which is thought to be due, in part, to impaired local vasodilatory mechanisms. Recent evidence suggests that folic acid improves cutaneous vasodilation during localized and whole‐body heating through nitric oxide‐dependent mechanisms. However, it is unclear if fol...
Article
Following a burn injury, excision of injured skin and subsequent grafting lead to attenuated sweating rates and thereby a diminished capacity for evaporative heat loss, resulting in exacerbated elevations in core temperature and greater risk of heat illness during physical activities. Since the capacity for evaporation is dependent on the absolute...
Article
Whole‐body heat stress increases cardiac output in younger and older individuals (i.e. ≥60 years), though the magnitude of that increase is attenuated in the older group. Recently, it has been identified that attenuated increases in cardiac output in older individuals during heat stress is primarily due to diminished heart rate responses. However,...
Article
Heat stress followed by an accompanying hemorrhagic challenge may influence hemostasis. We tested the hypothesis that hemostatic responses are increased by passive heat stress, and exercise-induced heat stress, each with accompanying central hypovolemia to simulate a hemorrhagic insult. In Aim 1, subjects were exposed to passive heating or normothe...
Article
New findings: What is the central question of this study? Does folic acid supplementation alleviate thermoregulatory and cardiovascular strain of older adults during exposure to extreme heat and humidity? What is the main finding and its importance? Folic acid supplementation for 6 weeks did not affect whole-limb blood flow/vasodilatation, core an...
Article
Cutaneous microvascular function is reduced with advancing age. Recent evidence suggests that chronic local heating of a limb improves cutaneous microvascular function in young healthy humans through nitric oxide‐dependent mechanisms. However, exposure to chronic heating of limb has not been studied in aged adults. The purpose of this study was to...