Sedentary Time After Cardiac Rehab Linked to Poor CR Fitness

Deborah Brauser

December 07, 2015

OTTAWA, ON — Spending large amounts of time participating in sedentary behaviors, such as watching TV and checking the computer, by patients with CAD can worsen various cardiometabolic markers—even if the patients also spend  time exercising, new research suggests[1].

Secondary analysis of the Efficacy and Economics of Exercise Maintenance Post-Cardiac Rehabilitation (ECO-PCR) study of 263 patients at centers in Canada, all of whom had recently completed a cardiac rehab program emphasizing the importance of exercise, showed that accelerometer-measured sedentary time averaged almost 8 hours per day and was significantly associated with low VO2peak (a marker of poor cardiorespiratory [CR] fitness), as well as low levels of HDL cholesterol, high body-mass index (BMI), and high triglycerides.

The association between high sedentary time and VO2peak and BMI remained significant (P=0.003 and 0.03, respectively) even after adjustment for variables such as age, sex, and medication use.

In addition, the male participants had nearly 1 hour of more sedentary time each day vs the female participants, possibly due to the latter group participating in more light-intensity daily-living movements, such as running errands or cleaning house. Still, even the women's sitting time was much more than it should be, note the investigators, led by Dr Stephanie A Prince (University of Ottawa Heart Institute, Ontario).

The overall results showed that, even among a patient population expected to be more active than other CHD patients, sedentary time remained high and was linked to poor CR fitness, "suggesting a possible new area of focus" for future interventions, write the researchers.

The findings were published online November 25, 2015 in the European Journal of Preventive Cardiology.

Strong Associations

Cardiac rehab "is an evidence-based standard of care" for patients who have had a cardiac condition and recommends 30 to 60 minutes per day of moderate-to-vigorous physical activity (MVPA), note the investigators.

In this analysis, they examined 263 ECO-PCR participants with CAD who had undergone supervised cardiac rehab programs. All of the rehab graduates wore accelerometers during waking hours, which was defined as at least 10 hours per day for at least 7 days.

The full group of participants had a mean total of 468.9 minutes of sedentary time per day; the men had 483.6 minutes per day vs 424.2 minutes per day for the women (P<0.0001).

In addition, the men had more sedentary breaks (13.4 vs 11 per day, respectively; P<0.0001) but less light-activity time (306.3 vs 356.3 minutes/day, P<0.0001).

However, the men did have more total MVPA minutes per day vs the women (46.1 vs 38.1, P=0.03).

Significant correlations were found between sedentary time in the full group and high BMI (P=0.009), waist circumference (P=0.007), and triglycerides (P=0.03); and between sedentary time and low HDL (P=0.005) and VO2peak (P=0.02).

In addition, "for every 1-hour increase in sedentary time per day, waist circumference increased by ~2 cm and VO2peak decreased by 1.05 mL/kg/min," write the investigators. "Adjusting for MVPA did not change the strength of the association."

After full adjustments, the strongest association with sedentary time was found for logVO2peak, which "is of particular importance given the prognostic value of cardiorespiratory fitness on cardiovascular health and mortality."

The researchers note that because CR fitness is a key indicator of how well a particular cardiac rehabilitation program works, "sedentary time may offer a unique opportunity to improve outcomes." However, more longitudinal and/or interventional studies are now needed to look into these issues, they conclude.

The ECO-PCR study was funded by a grant from the Heart and Stroke Foundation of Ontario. Prince is funded by fellowships from the University of Ottawa Heart Institute Foundation and from the Canadian Institutes of Health Research. She and the coauthors report no relevant financial relationships.

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