Numerous studies have shown the role of physical activity in improving heart health in patients with type 2 diabetes. However, it was largely unknown whether training at a certain time of the day promised an additional health bonus for this population.
New research published in Diabetes Care reports a correlation between timing of moderate to vigorous physical activity and cardiovascular fitness and health risks for people with type 2 diabetes and obesity or overweight.
The research team of researchers at Brigham and Women’s Hospital and Joslin Diabetes Center and staff found that men who did physical activity in the morning were at the highest risk of developing coronary artery disease (CHD) regardless of their study of 2,035 people become ill with the amount and intensity of weekly physical activity. The most active men at noon had lower cardiorespiratory fitness. In women, the researchers found no connection between the specific time of activity and the risk of CHD or cardiorespiratory fitness.
“The general message to our patient population remains that you should exercise whenever you can, as regular exercise offers significant health benefits,” said author Jingyi Qian of Brigham’s Sleep and Circadian Disorders Division and instructor for medicine at Harvard Medical School. “However, researchers studying the effects of physical activity should consider timing as an additional consideration so that we can provide better advice to the public about how the time of day can affect the relationship between exercise and cardiovascular health.”
The researchers analyzed baseline data from the Look AHEAD (Action for Health in Diabetes) study, a multi-site randomized clinical trial that began in 2001 that monitored the health of more than 5,000 people with type 2 diabetes and being overweight or obese. Among them, over 2,000 people had objectively measured physical activity at the start of the study.
“The study population was very well characterized at the start of the study, with detailed measurements of metabolic and physical activity, which was an advantage of using this data set for our work,” said author Roeland Middelbeek of the Joslin Diabetes Center, who is a co-researcher of the Look AHEAD study.
For the article on Diabetes Care, researchers reviewed data from hip accelerometers that participants wore for a week at the start of the Look AHEAD study. Researchers tracked the “time” of moderate to vigorous daily activity, including labor-intensive work that went beyond more traditional forms of exercise. To assess participants’ risk for CHD over the next four years, the researchers used the well-known Framingham gender-specific risk score algorithm.
Gender-specific physiological differences can help explain the more noticeable correlations found in men who are at risk for CHD earlier in life. However, the researchers note that other factors could also play a role. It remains unclear why time-specific activities can be associated with different health and fitness levels.
The researchers were also unable to take into account the different circadian rhythms of the participants: while jogging at 6 p.m. can be an “evening exercise” for one participant, another participant who wakes up later in the day can biologically be viewed as “afternoon”. regardless of how the time of the activity was recorded in the study.
“Interest in the interaction between physical activity and the circadian system is still emerging,” said Qian. “We developed a method of quantifying and characterizing participants based on the time of their physical activity that researchers can use to conduct other studies in other cohorts.”
In addition to further integrating circadian biology with exercise physiology, researchers also look forward to using longitudinal data to examine how timing of exercise affects cardiovascular health outcomes, especially in diabetic patients who are more prone to cardiovascular events.
Other contributors to the research include Michael P. Walkup, Shyh-Huei Chen, Peter H. Brubaker, Dale S. Bond, Phyllis A. Richey, John M. Jakicic, Kun Hu, Frank AJL Scheer, and the Look AHEAD Research Group.
Funding came from the National Institutes of Health. National Institute of the Heart, Lungs and Blood (K99HL148500). The Look AHEAD study was supported by the Department of Health and Human Services through the following National Institutes of Health Collaboration Agreements (DK57136, DK57149, DK56990, DK57177, DK57171, DK57151, DK57182, DK57131, DK57002, DK57078, DK57, DK57219, DK57008, DK57135 and DK56992). The Indian Health Service (IHS) provided staff, medical supervision and use of the facilities.