Missed Opportunity? Exercise Benefits Sedentary Seniors But Does Not Reverse Cardiac Stiffening

Reed Miller

October 26, 2010

October 26, 2010 (Dallas, Texas) — Exercise cannot reverse the cardiac stiffening effect of years of sedentary behavior in people over 65, but it can improve arterial function and aerobic capacity and induce left-ventricular remodeling, results of a study published online October 18, 2010 in Circulation show [1].

Previous research has shown that the left-ventricular compliance of older athlete "masters" who have exercised intensely for most of their adult lives is indistinguishable from that of healthy younger people, suggesting physical activity plays a critical role in maintaining cardiovascular health as people get older, according to Dr Naoki Fujimoto (University of Texas Southwestern Medical Center, Dallas) and colleagues.

However, it is not clear whether endurance exercise training later in life can reverse this stiffening process. So Fujimoto et al compared the effects of 12 months of regular endurance training in 12 previously sedentary people over 65 with that of 12 elite master athletes.

All subjects underwent invasive hemodynamic measurements with pulmonary artery catheterization to define their Starling and left-ventricular pressure-volume curves, as well as Doppler echocardiography, MRI assessment of cardiac morphology, total aortic compliance and arterial elastance measurements, and maximal exercise testing. Before training, the sedentary subjects had significantly lower VO2max, left-ventricular mass, left-ventricular end-diastolic volume, stroke volume, and left-ventricular compliance than the master athletes.

Nine of 12 sedentary seniors completed the year of endurance training. The year of exercise training had little effect on the measures of cardiac compliance, but it improved VO2max 19% (22.8 vs 27.2 mL/kg/mL; p<0.001) and increased left-ventricular mass by an average of 10% (64.5 vs 71.2 g/m2; p=0.037) without changing the mass-volume ratio.

"We hoped we'd see structural changes in the heart and blood vessels--that the hearts would become bigger and more compliant and the blood vessels would become more compliant, but what we found was that we couldn't touch the structure of either the heart or the blood vessels," coauthor Dr Benjamin Levine (University of Texas Southwestern Medical Center) told heartwire . Improvements in function without structural improvement suggest that the exercise improved ventricular-arterial coupling with improved large-vessel endothelial function in these patients, Levine said. "It was a functional change, but not a structural change," he said.

The authors offer several possible explanations for why neither the left-ventricular pressure-volume curves nor individual left-ventricular stiffness improved after a year of training. It is possible that in persons over 65 it is too late to reverse the stiffening effects of sedentary aging. Cardiovascular aging is characterized by cross-linked advanced glycation end products in vascular and left-ventricular walls and changes in the number and volume of cardiac myocytes, and since these proteins are pathologically irreversible once formed, improvements in left-ventricular compliance from increases in protein content could have been constrained by cross-linked collagen, the authors explain.

Levine said that his group is studying how much exercise an older adult needs to do to improve cardiovascular health. "It's not a very efficient public-health strategy for everyone to have to train as much as a master athlete," so his group is currently preparing a study derived from the Cooper Center Longitudinal Study comparing different levels of weekly exercise. The results so far suggest that exercising two or three times a week does not have much effect but that committed exercisers who work out four or five times a week get almost the same benefits as the competitive athletes who train at least six days a week and regularly participate in organized competitions, Levine said.

His group is also working to identify the age at which the cardiac stiffening process begins. Data from the Dallas Heart Study suggests that the heart starts to stiffen sometime between the ages of 45 to 65. So Levine's group is planning a study of patients ages 45 to 64 training four or five days a week with a combination of endurance training and high-intensity intervals (four minutes at 95% of maximum heart rate followed by three minutes of recovery, repeated four times).

Levine's group is also investigating alagebrium, a cross-link-breaking drug that has been shown to improve left-ventricular and arterial stiffness in animals and therefore might be able to reverse cardiovascular stiffening in the elderly. Levine's group is currently recruiting for a randomized trial (The Effect of Exercise and Alagebrium on the Diastolic Function of the Heart [AGE]) that will study whether alagebrium therapy in conjunction with exercise training reverses the stiffening of the aging heart.