Prolonged Sitting Time Linked to CVD Events, Mortality

Megan Brooks

June 17, 2022

A new analysis using data from the Prospective Urban Rural Epidemiology (PURE) study shows that sitting more than 8 hours per day was associated with an increased risk of a composite of all-cause death and cardiovascular disease (CVD) events.

In this study that tracked over 100,000 adults from 21 countries for 8 to 12 years, more time spent sitting during the day was associated with increased risk of early death and CVD events, including cardiovascular death, myocardial infarction (MI), stroke, or heart failure.

The combination of prolonged sitting and physical inactivity was particularly harmful, accounting for nearly 9% of all deaths.

"This is close to the contribution of smoking (10.6% in our study)," Scott Lear, PhD, with Simon Fraser University, Vancouver, British Columbia, told | Medscape Cardiology. Importantly, the increased risks of prolonged sitting were offset by increased physical activity, he said.

The observation held across the economically diverse settings in this study and was even more pronounced in lower- and lower-middle-income countries, they note. "Reducing sedentary time and along with increasing physical activity might be an important strategy for easing the global burden of premature deaths and CVD," the authors conclude.

The study was published online June 15 in JAMA Cardiology.

The findings are based on data from 105,677 adults aged 35 to 70 years (mean age, 50 years; 59% women) from the PURE cohort. During a median follow-up of 11 years, there were 6233 deaths and 5696 major CVD events.

In multivariable adjusted models, compared to those who sat for fewer than 4 hours per day, those who sat for 8 or more hours per day had a 20% higher risk for all-cause death (hazard ratio [HR], 1.20; 95% CI, 1.1 – 1.31; P for trend < .001) and a 21% higher risk for major CVD (HR, 1.21; 95% CI, 1.1 – 1.34; P for trend < .001).

Sitting for 6 to 8 hours per day was associated with a 12% increased risk for death (HR 1.12; 95% CI, 1.03 – 1.21; P for trend < .001) and a 13% increased risk for major CVD (HR, 1.13; 95% CI, 1.04 – 1.23; P for trend < .001).

The association held for high-, middle-, and low-income countries but was stronger in low-income and lower-middle-income countries.

"We can only speculate why, but it may be due to socioeconomic factors, such that sitting in high-income countries is associated more with higher-paid jobs and higher socioeconomic status," Lear said.

"If you must sit, getting in more exercise at other times during the day can help offset the risks," he noted.

In the study, those who sat for 8+ hours per day and were the least active had the highest risk (up to 50% greater). In contrast, in those who sat the most but were most active, the risk was only 17%. Those who sat the least and were the most active had the lowest risk.

"It's important for clinicians to realize the scope of the problem and how substantially sitting and physical inactivity contribute to disease," Lear told | Medscape Cardiology.

He encourages clinicians to focus on the "low-cost intervention of promoting physical activity and reducing sitting time. Clinicians too, should take these findings to heart and ensure they are following the activity guidelines to ensure they are maintaining their health," Lear said.

Reached for comment, Harlan Krumholz, MD, with Yale New Haven Hospital and Yale School of Medicine, New Haven, Connecticut, said it's "always challenging to make causal inferences from observational data, but this is a well-done study of a massive and diverse population.

"The association of sedentary behavior with adverse outcomes is plausible, and the solution, more physical activity, has little downside and much upside," Krumholz said.

"As our society increasingly drifts toward more screen time and less physical activity, we need to consider what effects that might have on our long-term health and function," he said.

"Humans seem built to move ― and to suffer if we do not. This article certainly supports my bias toward encouraging people to be active and stay active as a way to promote health and lifelong function," Krumholz added.

The PURE study is funded by the Population Health Research Institute, the Hamilton Health Sciences Research Institute, the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario, the Canadian Institutes of Health Research's Strategy for Patient Oriented Research through the Ontario SPOR Support Unit, the Ontario Ministry of Health and Long-Term Care, and through unrestricted grants from AstraZeneca (Canada), Sanofi-Aventis (France and Canada), Boehringer Ingelheim (Germany and Canada), Servier, and GlaxoSmithKline, and additional contributions from Novartis and King Pharma and from various national or local organizations in participating countries. Lear and Krumholz have disclosed no relevant financial relationships.

JAMA Cardiol. Published online June 15, 2022. Abstract

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