Is exercising late in the morning associated with a reduced risk of cardiovascular disease?

Is exercising late in the morning associated with a reduced risk of cardiovascular disease?

Cardiologue et Directeur de la prévention, Institut de Cardiologie de Montréal. Professeur titulaire de clinique, Faculté de médecine de l'Université de Montréal. / Cardiologist and Director of Prevention, Montreal Heart Institute. Clinical Professor, Faculty of Medicine, University of Montreal.14 December 2022

OVERVIEW

  • Participants in a study who exercised in the late morning had a 16% lower risk of a coronary event and a 17% lower risk of a stroke compared to those who exercised at another time of day.
  • These effects were particularly pronounced in women, but are non-significant when considering data for men only.
  • These results illustrate the potential importance of chronoactivity in the prevention of cardiovascular disease.

Is it better to exercise in the morning or later in the day to reduce the risk of cardiovascular disease? This is a question that Dutch researchers have tried to answer in a study of 86,657 participants in the UK-Biobank cohort, aged 62 on average. Participants’ physical activity data was collected at the start of the study using a wrist-worn triaxial accelerometer over a 7-day period. Six years after the start of the study, 3,707 cardiovascular events had been reported. Participants who exercised late in the morning had a 16% lower risk of a coronary event and a 17% lower risk of a stroke, compared to those who exercised at another time of day.

These effects were particularly pronounced in women. In contrast, most of the favourable associations of morning physical activity disappeared when the researchers analyzed data from men only. This difference remains unexplained and raises the possibility that a confounding factor may be the cause. Do women who exercise in the morning have better lifestyle habits, unrelated to physical exercise, such as better diet?

Previous studies had shown a favourable association between morning physical activity and better cardiometabolic health, both for obesity (see here, here and here), type 2 diabetes, and hypertension. However, a number of studies have shown completely opposite results. For example, a recent study in Brazil indicates that for hypertensive men, evening exercise was more effective than morning exercise in restoring the heart rate and lowering blood pressure. Additionally, a Swedish study of men with type 2 diabetes indicates that high-intensity interval training (HIIT) performed in the afternoon was more effective than morning exercise in improving blood sugar levels. It should be noted that these last two intervention studies are of the “randomized and controlled” type, a study design that provides a relatively high level of scientific evidence, even if these studies were carried out with a small number of participants.

Further studies will be needed to better understand the chronoactivity phenomena, but regardless of whether it is done in the morning, afternoon or evening, it is well established that physical exercise is beneficial for cardiovascular health, mental health and overall health.

Walking in the forest has positive impacts on the brain

Walking in the forest has positive impacts on the brain

Professeur titulaire au Département de Médecine de l’Université de Montréal. Directeur du Centre ÉPIC de l’Institut de cardiologie de Montréal.12 December 2022

A multitude of studies have shown that the interaction of humans with nature generates several positive effects on health, both physically and psychologically. A recent review of these studies (in French), recently carried out by our team, revealed that these beneficial effects are particularly compelling with regard to the reduction of stress and anxiety that results from an interaction with a natural environment.

Decreased activity of the amygdala
To better understand the mechanisms involved in this nature-mediated stress reduction, a team of German researchers investigated the potential involvement of the amygdala, a region of the brain that plays a predominant role in the stress response.

In this study, the researchers recruited 63 participants and randomly divided them into two groups: 1) a “city” group, in which the volunteers (31 participants) had to walk for one hour in an urban area (a commercial street in Berlin) and 2) a “nature” group, in which the volunteers (32 participants) also had to walk for an hour, but this time in nature (the Grunewald forest, located southwest of Berlin).

By measuring the activity of the amygdala of all participants using functional magnetic resonance imaging (fMRI), before and after their assigned route, the researchers observed major differences between both groups: while walking in urban areas had no measurable effect, walking in the forest caused a significant decrease (about 50%) in participants’ amygdala activity. Moreover, this effect was observed equivalently when the participants were exposed to images of neutral faces or to faces expressing fear, which are supposed to induce a higher stress response. It therefore seems that simply interacting with nature for a short period of time is enough to positively influence the brain centre involved in stress.

Even if it is at this stage premature to conclude that this decrease in amygdala activity alone is responsible for the soothing properties of nature, these results nevertheless remain very interesting, because they show for the first time that interacting with nature has measurable positive effects on the activity of certain areas of the brain, particularly in an area involved in the stress response.