Differences in Mortality at the Low End of the Fitness Spectrum
Purpose: A graded nonlinear relationship exists between fitness and mortality with the most remarkable difference in mortality rates observed between the least-fit (first, Q1) and the next-least-fit (second, Q2) quintile of fitness. The purpose of this study was to compare clinical characteristics, exercise test responses, and physical activity patterns in Q1 versus Q2 in apparently healthy individuals.
Methods: A total of 4384 subjects referred for clinical treadmill testing from 1986 to 2006 were followed for a mean ± SD period of 8.7 ± 5.3 yr. All subjects had normal exercise ECG responses and no history of cardiovascular disease. Subjects were classified into quintiles of exercise capacity measured in METs. Clinical characteristics, physical activity patterns, and treadmill test results were compared between the first two quintiles (Q1: METs < 5.9 (n = 693); Q2: METs 6.0-7.9 (n = 842)).
Results: Small differences in age (64 ± 11 vs 60 ± 10 yr, P < 0.001), use of antihypertensive medications, prevalence of diabetes (21% vs 16%, P = 0.02), and dyslipidemia (43% vs 49%, P = 0.04) were observed between Q1 and Q2. When the Cox proportional hazards model was adjusted for age and other clinical characteristics, the relative risk of mortality remained almost two times greater in Q1 versus Q2 (cardiovascular mortality: HR: 4.01 vs 2.01, P < 0.001; reference group: fittest subjects (Q5)). In a subset of 802 subjects, recent recreational physical activity was significantly lower in Q1 versus Q2.
Conclusions: Reduced physical activity patterns rather than differences in clinical characteristics contribute to the striking difference in mortality rates between the least-fit and the next-least-fit quintile of fitness in healthy individuals.
Numerous epidemiological studies in recent years have reported an inverse, graded, and dose-dependent relationship between physical fitness and mortality in individuals with and without cardiovascular disease. Accumulating evidence suggests that this relationship is nonlinear, with the greatest decline in risk of mortality occurring between the least-fit (first, Q1) and the next-least-fit (second, Q2) quintile of fitness. These findings have led the current consensus statements on physical activity to emphasize that the greatest health benefits are achieved by increasing physical activity among the least-fit individuals. However, factors that may explain the steep mortality gradient at the lowest end of the fitness spectrum have not been explored. Therefore, it remains unknown whether differences in clinical characteristics (reflecting differences in severity of underlying disease), physical activity patterns, other behaviors, environmental, or other factors such as genetics could explain the steep mortality gradient between Q1 and Q2. The purpose of this retrospective study was to compare clinical characteristics, exercise test responses, and physical activity patterns between Q1 and Q2 in apparently healthy individuals.
Abstract and Introduction
Abstract
Purpose: A graded nonlinear relationship exists between fitness and mortality with the most remarkable difference in mortality rates observed between the least-fit (first, Q1) and the next-least-fit (second, Q2) quintile of fitness. The purpose of this study was to compare clinical characteristics, exercise test responses, and physical activity patterns in Q1 versus Q2 in apparently healthy individuals.
Methods: A total of 4384 subjects referred for clinical treadmill testing from 1986 to 2006 were followed for a mean ± SD period of 8.7 ± 5.3 yr. All subjects had normal exercise ECG responses and no history of cardiovascular disease. Subjects were classified into quintiles of exercise capacity measured in METs. Clinical characteristics, physical activity patterns, and treadmill test results were compared between the first two quintiles (Q1: METs < 5.9 (n = 693); Q2: METs 6.0-7.9 (n = 842)).
Results: Small differences in age (64 ± 11 vs 60 ± 10 yr, P < 0.001), use of antihypertensive medications, prevalence of diabetes (21% vs 16%, P = 0.02), and dyslipidemia (43% vs 49%, P = 0.04) were observed between Q1 and Q2. When the Cox proportional hazards model was adjusted for age and other clinical characteristics, the relative risk of mortality remained almost two times greater in Q1 versus Q2 (cardiovascular mortality: HR: 4.01 vs 2.01, P < 0.001; reference group: fittest subjects (Q5)). In a subset of 802 subjects, recent recreational physical activity was significantly lower in Q1 versus Q2.
Conclusions: Reduced physical activity patterns rather than differences in clinical characteristics contribute to the striking difference in mortality rates between the least-fit and the next-least-fit quintile of fitness in healthy individuals.
Introduction
Numerous epidemiological studies in recent years have reported an inverse, graded, and dose-dependent relationship between physical fitness and mortality in individuals with and without cardiovascular disease. Accumulating evidence suggests that this relationship is nonlinear, with the greatest decline in risk of mortality occurring between the least-fit (first, Q1) and the next-least-fit (second, Q2) quintile of fitness. These findings have led the current consensus statements on physical activity to emphasize that the greatest health benefits are achieved by increasing physical activity among the least-fit individuals. However, factors that may explain the steep mortality gradient at the lowest end of the fitness spectrum have not been explored. Therefore, it remains unknown whether differences in clinical characteristics (reflecting differences in severity of underlying disease), physical activity patterns, other behaviors, environmental, or other factors such as genetics could explain the steep mortality gradient between Q1 and Q2. The purpose of this retrospective study was to compare clinical characteristics, exercise test responses, and physical activity patterns between Q1 and Q2 in apparently healthy individuals.