Sedentary Time Ups CVD Risk in Dose-Response Way: Study

Larry Hand

July 22, 2016

DALLAS, TX — A new study has found that sedentary time is associated with increased risk of cardiovascular disease (CVD) only if total sedentary time comes to more than 10 hours a day[1].

The findings could have implications for future guideline recommendations related to sedentary behavior, according to researchers, especially for individuals whose comorbidities limit their ability to meet guideline-recommended physical-activity levels.

"Sedentary time at very high levels is associated with a higher risk of cardiovascular disease independent of other well-established risk factors, including low physical activity and high body-mass index," Dr Ambarish Pandey (University of Texas Southwestern Medical Center, Dallas) told heartwire from Medscape by email.

Pandey and colleagues conducted a meta-analysis of nine prospective cohort studies published before July 6, 2015 covering 720,425 participants (mean age 54.5, 57.1% women) and 25,769 unique cardiovascular events. Median follow-up came to 11 years.

The meta-analysis was published online July 13, 2016 in JAMA Cardiology. The studies assessed sedentary behavior by self-report.

In the current study, researchers found that participants who reported the highest sedentary times (mean 12.5 h/day) had an increased risk for CVD (pooled HR 1.14) compared with participants who reported the least amount of sedentary time (mean 2.5 h/day). They found the association between participants with intermediate sedentary time, compared with least sedentary time, to be not clinically significant.

"In continuous analyses, we found a nonlinear association between sedentary time and CVD risk (P<0.001 for nonlinearity), with a nonsignificant increased risk observed only at sedentary times more than 6.8 h/day (pooled HR 1.01; 95% CI 0.95–1.08), and that became statistically significant at times more than 10.0 h/day (pooled HR 1.08; 95% CI 1.00–1.14)," the researchers wrote.

As far as future recommendations, the study provided "important insights into the thresholds beyond which sedentary time may be detrimental to CV health," they wrote. Reductions in sedentary time may be especially relevant for individuals who, because of comorbidities or other limitations, might not be able to meet guideline-recommended physical-activity levels of 30 minutes of moderate to vigorous activity most days of the week.

Because of conflicting studies in the literature, "The exact levels of sedentary time that should be avoided to lower CVD risk is not known. Our study-level meta-analysis provided a unique opportunity to evaluate the dose-response relationship between sedentary time and CVD risk by pooling data from all the available studies in this area," Pandey told heartwire.

"Clinicians should advise patients to avoid prolonged sedentary durations in their day-to-day life. Increasing physical activity and workplace interventions such as sit-stand workstations and activity-permissive desks may be useful to lower sedentary time," he said.

In a meta-analysis published last year, researchers found prolonged sitting to be associated with all-cause mortality, cancer, CVD, and type 2 diabetes, also independent of physical-activity level.

The study was funded by the Dedman Family Scholar in Clinical Care Endowment and American Heart Association. The authors reported no relevant financial relationships.

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