Patients with heart disease who sit a lot have worse health even if they include exercise in their lives. That is the conclusion of new findings that looked at the activity levels and corresponding health indicators of patients with coronary artery disease.
“Limiting the amount of time we spend sitting may be as important as the amount we exercise,” said lead author Stephanie Prince, PhD, post-doctorate fellow in the Division of Prevention and Rehabilitation at the University of Ottawa Heart Institute. “Sitting, watching TV, working at a computer and driving in a car are all sedentary behaviours and we need to take breaks from them.”
Previous research has shown that being sedentary increases the risk of cardiovascular disease, but until now, its effect on patients with established heart disease was unknown.
The current study, published in November in the European Journal of Cardiovascular Prevention, investigated levels of sedentary behaviour and the effect on health in 278 patients with coronary artery disease. The patients had been through a cardiac rehabilitation programme which taught them how to improve their levels of exercise in the long term.
Patients wore an activity monitor during their waking hours for nine days. The monitors allowed the researchers to measure how long patients spent being sedentary, or doing light, moderate or vigorous levels of physical activity.
The researchers also assessed various markers of health including BMI and cardiorespiratory fitness to determine whether the amount of time a person spent being sedentary (mainly sitting) was related to these markers.
The patients spent an average of eight hours each day being sedentary. “This was surprising given that they had taken classes on how to exercise more,” said Dr. Prince. “We assumed they would be less sedentary but they spent the majority of their day sitting.”
Men spent more time sitting than women—an average of one additional hour each day. This difference was primarily because women tended to do more light-intensity movement—things like light housework, walking to the end of the drive, or running errands.
Dr. Prince said: “Women with coronary artery disease spend less time sitting for long periods, but we need to do more research to understand why. There is some research which suggests that at around the age of 60 men become more sedentary than women and may watch more TV.”
The patients who sat more had a higher BMI and had lower cardiorespiratory fitness. This was assessed using their aerobic capacity. This is the maximum rate at which the heart, lungs and muscles use oxygen during an exercise test.
“These relationships remained even when we controlled for an individual’s age, gender or physical activity levels,” said Dr. Prince. “In other words, people who sat for longer periods were heavier and less fit regardless of how much they exercised.”
Dr. Prince emphasized that sitting less was not a replacement for exercise. “It’s important to limit prolonged bouts of sitting and in addition to be physically active,” she said. “Sedentary time may be another area of focus for cardiac rehabilitation programmes along with exercise.”