While the risk of stroke increased more than fourfold among sedentary people under the age of 60, no significant increase in risk was observed among older individuals, according to the study based on self-reported data from more than 140,000 people. This highlights the need for relevant public health messaging directed at younger people, reported lead author, Raed A. Joundi, MD, DPhil, a stroke fellow at the University of Calgary (Alta.), and colleagues, in the paper published in Stroke.
“Sedentary time has increased over the past 2 decades in the United States and Canada, particularly in the young, raising the importance of characterizing its effect on long-term health , ” the investigators wrote. “A better understanding of the risk of sedentary time specific to stroke may be important for public health campaigns to reduce sedentary behavior.” Dr. Joundi and colleagues reviewed data from the Canadian Community Health Survey, including 143,180 healthy individuals without baseline history of cancer, heart disease, or stroke. Those under the age of 40 years were also excluded from the analysis.
Excess sedentary leisure time was defined as 8 or more hours of sedentary leisure time per day, whereas low physical activity was defined as less than 3.5 metabolic equivalent hours per week. The analysis also included a range of demographic and medical covariates, such as age, sex, marital status, smoking status, presence of hypertension, and others.
After a median follow-up of 9.4 years, 2,965 stroke events occurred, with a median time from survey response of 5.6 years. Risk of stroke among individuals aged younger than 60 years who engaged in low physical activity and excess sedentary leisure time was increased 4.5-fold, compared with individuals with low physical activity who were sedentary less than 4 hours per day (fully adjusted hazard ratio, 4.50; 95% confidence interval, 1.64-12.3).
Findings highlight benefits of physical activity
Similar risk elevations were not observed among individuals aged 60-79 years, or those older than 80. And among people younger than 60, high physical activity appeared to eliminate the additional risk imposed by excess sedentary leisure time.
“Sedentary time is associated with higher risk of stroke in inactive individuals, but not an active individual, ” Dr. Joundi said in an interview. “So it suggests that there’s two ways to lower risk: One would be to lower your sedentary time, and the other would be to engage in physical activity.”
These interpretations are speculative, Dr. Joundi cautioned, as the study was not interventional. Even so, he said that the findings “bring the spotlight back on physical activity,” thereby aligning with previous research.
“The more you exercise, the more that relationship between sedentary time and poor health outcomes is blunted, and in fact, can be completely negated with enough physical activity,” he said.
How exactly physical activity offers such protection remains unclear, Dr. Joundi added. He speculated that regularity of exercise may be key, with each session counteracting the adverse effects of prolonged sedentary time, which may include reduced blood flow, increased insulin resistance, and inflammatory changes that can affect blood vessels.
“This study is particularly a message for younger individuals,” Dr. Joundi said, suggesting that the findings may alter behavior, as many people have witnessed, or are aware of, the long-term impacts of stroke.
“There’s a sort of social or cognitive aversion to stroke, I think, in the general population, because of how disabling it can be, and how it can lower your quality of life,” he said.
Subtle lifestyle changes may be enough.
For those aiming to lower their risk of stroke, Dr. Joundi suggested that subtle lifestyle changes may be enough.
“Ultimately, what we saw is that even minimal amounts of physical activity – walking 3 hours a week, for example – could blunt the impact of sedentary time,” he said. “Doing what you can, even if it’s a small amount, tends to be quite meaningful over a long period of time.”
Daniel T. Lackland, DrPH, professor of epidemiology in the department of neurology at the Medical University of South Carolina, Charleston, offered a similar takeaway, noting that small efforts can lead to great benefits.
“Less intense activity is still better than being sedentary,” he said in an interview. “For many people, if you do get up and you just walk around, move your arms around – do any kind of movement – that’s better than being sedentary.”
Dr. Lackland applauded the practicality of studying sedentary leisure time, versus overall leisure time, as many people can’t control their work environment.
“You can’t do very much about how you work your job,” Dr. Lackland said. “Sometimes we have to sit, and I guess there are things you can do – you can put a treadmill instead of a chair and that kind of thing – but more often than not, you don’t really have that choice to do something. With leisure time, though, you’re in full control. And so what do you do with your leisure time? Do you sit and watch TV, or do you engage in some type of activity? Not necessarily aerobic activity, but some type of activity that would not let you be sedentary. You want to be active as much as you possibly can.”
Dr. Joundi disclosed grant support from the Canadian Institutes of Health Research. The other investigators and Dr. Lackland reported no relevant disclosures.