Numerous studies have shown the role of physical activity in improving heart health in patients with type 2 diabetes. But whether exercise at certain times of the day promised an additional health bonus for this population was still largely unknown.
A new study published in the journal Diabetes Care reports on a correlation between time to moderate to vigorous physical activity and cardiovascular fitness and health risks for people with type 2 diabetes and obesity or overweight.
A research team from Brigham and Women’s Hospital and Joslin Diabetes Center, along with colleagues, found that in a study of 2,035 people, men who exercised in the morning had the highest risk of developing coronary heart disease (CHD), regardless of the amount and intensity physical activity weekly. The men most active at noon had a lower level of cardiorespiratory fitness. In women, the researchers did not find a link between a specific time of activity and the risk of CHD or cardiorespiratory condition.
“The general message for our patient population is that you need to exercise whenever you can because regular exercise brings significant health benefits,” said co-author Jingyi Qian of Brigham’s Department of Sleep Disorders and Circadian Diseases and a medical instructor at Harvard Medical School. “But researchers studying the effects of physical activity should consider time as an additional consideration so we can make better recommendations to the general 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 study, a multicellular, randomized clinical trial that began in 2001 and monitored the health of more than 5,000 people with type 2 diabetes and overweight or obesity. Among them, over 2,000 people objectively measured physical activity at baseline.
“The study population was very well characterized at baseline, with detailed measurements of metabolism and physical activity, which was an advantage of using this dataset for our work,” said lead author Roeland Middelbeek of the Joslin Diabetes Center, a co-researcher at Look AHEAD. .
For diabetes care the researchers reviewed hip accelerometer data that participants wore for one week at the start of the Look AHEAD study. The researchers tracked the “time” of daily moderate to vigorous activities, including work-intensive work that extends beyond more traditionally defined forms of exercise. To assess participants’ risk levels of having CHD over the next four years, the researchers used the well-known Framingham risk assessment algorithm.
Gender-specific physiological differences may help explain the more pronounced correlations seen in men who tend to be at risk for CHD earlier in life. However, researchers note that other factors could be at play. It remains unclear why timed activities may be associated with different levels of health and fitness.
The researchers also could not explain the different circadian rhythms of the participants: while running at 6 pm for one participant can be an “evening exercise”, another participant prone to waking up later in the day may, biologically, consider it “afternoon”. regardless of how the activity time was recorded in the study.
“Interest in the interaction between physical activity and the circadian system is still emerging,” Qian said. “We have formed a methodology for quantifying and characterizing participants based on the time of their physical activity, which allows researchers to conduct other studies in other groups.”
In addition to further integrating circadian biology with exercise physiology, researchers are also excited to use longitudinal data to investigate how exercise time relates to cardiovascular health outcomes, especially among diabetic patients who are more vulnerable to cardiovascular events.
Other research collaborators include Michael P. Walkup, Shyh-Huei Chen, Peter H. Brubaker, Dale S. Bond, Phyllis A. Richey, John M. Jakičić, Kun Hu, Frank AJL Scheer, and the Look AHEAD research group.
Funding was provided by the National Institutes of Health. National Heart, Lung and Blood Institute (K99HL148500). The Look AHEAD experiment was supported by the Department of Health and Social Services with the following cooperation agreements with the National Institutes of Health (DK57136, DK57149, DK56990, DK57177, DK57171, DK57151, DK57182, DK57131, DK57002, DK57078, DK57154, DK57178, DK5 and DK56992). The Indian Health Service (IHS) provided staff, medical supervision and use of the facilities.