Too much sedentary time may up stroke risk

Spending excessive time being sedentary (≥8 hours/day) is associated with an increased risk of stroke in adults younger than 60 years old, particularly in those who also have little physical activity, a study suggests. 

Adults aged <60 years who spent ≥8 hours a day during their free time engaging in sedentary activities — such as watching TV, using a computer, or reading — and who also had low levels of physical activity* showed more than fourfold higher risk of stroke than their counterparts with <8 hours of leisure sedentary time (adjusted hazard ratio [HR], 4.50, 95 percent confidence interval [CI], 1.64–12.3). [Stroke 2021;doi:10.1161/STROKEAHA.121.034985]

The association remained after controlling for demographic, vascular, and social factors such as sex, body mass index, ethnicity, diabetes, hypertension, comorbidities, smoking status, alcohol consumption, income, education, and marital status, among others.

“Adults 60 years and younger should be aware that very high sedentary time with little time spent on physical activity can have adverse effects on health, including increased risk of stroke,” said lead author Dr Raed Joundi from the Cumming School of Medicine at the University of Calgary, Calgary, Canada.

“Physical activity has a very important role in that it reduces the actual time spent sedentary, and it also seems to diminish the negative impact of excess sedentary time,” he added.

For the study, leisure sedentary time is specifically examined, which refers particularly to sedentary activities performed while not at work, Joundi explained. 

The association between leisure sedentary time and increased stroke risk, however, was attenuated among individuals with high levels of physical activity.

Also, such association was only limited to adults younger than 60 years old and did not extend to older adults aged ≥60 years.

“The reason for the age-specific risk is unclear and may relate to longer follow-up in the younger population, selective survival in the older population, or accumulated confounding throughout the life span,” according to the researchers.

They believed that the potential mechanisms underlying the association between excess sedentary time and increased cardiovascular risk included reduction in blood flow, insulin resistance, and inflammatory changes that might impair vascular function. 

The study used health and lifestyle information of 143,180 adults with no history of heart disease, stroke, or cancer who responded to the Canadian Community Health Survey. The participants were followed for an average of 9.4 years on subsequent stroke-related hospitalization or emergency department visits based on hospital records. There were 2965 stroke events during follow-up.

“Our findings may have public health implications due to rising sedentary behaviour and stroke incidence in the younger population,” said Joundi and co-authors.

“Physician recommendations and public health policies should emphasize increased physical activity and lower sedentary time among young adults in combination with other healthy habits to lower the risks of cardiovascular events and stroke,” they urged.

*low physical activity: equivalent to 3.5 MET-hours/week or less