What Are the Effects of Fitness on BP Trajectory in Relation to Aging?
Investigating the effects of cardiorespiratory fitness on age-associated blood pressure (BP) changes, a new study has found that BP is inversely associated with fitness levels and people in higher fitness categories have lower BP than those in lower fitness categories, according to a study published Sept. 15 in the Journal of the American College of Cardiology. Further, the interaction between age and fitness was found to be significant for the systolic BP (SBP) trajectory, but not for diastolic BP (DBP), and the SBP trajectory increased linearly with age, while the DBP trajectory had a nonlinear relationship with aging.
Using data from the Aerobics Center Longitudinal Study from a cohort totaling 13,953 men aged 20 to 90 years who were free of hypertension, cardiovascular disease, and cancer and completed 3-28 follow-up examinations between 1970 and 2006, principle author Junxiu Liu, MD, PhD candidate, Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, SC, and colleagues found that in a linear mixed model, DBP tended to increase until nearly age 60, when a decrease was observed. At the same time SBP tended to increase over all age periods.
In a multivariable analysis, average SBP increased by 0.31 mm Hg (95 percent CI, 0.29 to 0.32) with one year age increments, after adjusting for body fat percentage, fitness, resting heart rate, glucose, triglycerides, cholesterol, current smoking, heavy alcohol drinking, and parental history of hypertension. DBP additionally increased with age, with a yearly increase of 0.15 mm Hg (95 percent CI, 0.14 to 0.16). Overall, abnormal SBP (>120 mm Hg) initiated at about age 50, while abnormal DBP (>80 mm Hg) began at to occur at age 60. Men who achieved higher fitness levels experienced abnormal SBP later than those with low fitness levels.
Given that elevated regular physical activity and aerobic exercise can yield significant SBP and DBP reductions, the study authors note that their study has "important clinical implications." While BP reductions ranging from two to five mm Hg for resting SBP and two to three mm Hg for resting DBP may appear small, they are clinically significant because it has been estimated that as little as a two mm Hg reduction in population average resting SBP can reduce coronary heart disease mortality by four percent, and reduction of five mm Hg can reduce coronary heart disease mortality by nine percent, they explain.
Inevitably the findings of the study underscore the potential modifying effect of fitness on BP trajectory with aging over the male adult life span. Promoting fitness to extend the duration of normal SBP levels is a simple and effective means to reduce the potential risk for developing hypertension, cardiovascular disease, and other BP-related chronic diseases, as well as reduce medical costs, major morbidity, and mortality.
In a related editorial comment, Stanley S. Franklin, MD, FACC, and Gary L. Pierce, PhD, add that, "indeed, habitual aerobic exercise/physical activity may even counteract the burden of cardiometabolic abnormalities that accelerate artery stiffening – characterized as 'early vascular aging' – and therefore, slow the onset and severity of isolated systolic hypertension." They note that moving forward, "future studies should investigate fundamental mechanisms of cardiorespiratory fitness that result in 'primordial' prevention of systolic hypertension with advancing age."
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