Role of lifestyle and aging on the longitudinal change in cardiorespiratory fitness

Abstract

Background: Cardiorespiratory fitness (CRF) in adults decreases with age and is influenced by lifestyle. Low CRF is associated with risk of diseases and the ability of older persons to function independently. We defined the longitudinal rate of CRF decline with aging and the association of aging and lifestyle with CRF.

Methods: We studied a cohort of 3429 women and 16 889 men, aged 20 to 96 years, from the Aerobics Center Longitudinal Study who completed 2 to 33 health examinations from 1974 to 2006. The lifestyle variables were body mass index, self-reported aerobic exercise, and smoking behavior. Cardiorespiratory fitness was measured by a maximal Balke treadmill exercise test.

Results: Linear mixed models regression analysis stratified by sex showed that the decline in CRF with age was not linear. After 45 years of age, CRF declined at an accelerated rate. For each unit of increase in body mass index, the CRF of women declined 0.20 metabolic equivalents (METs) (95% confidence interval, -0.21 to -0.19); that of men, 0.32 METs (-0.33 to -0.20). Current smokers of both sexes also had lower CRF (-0.29 METs [95% confidence interval, -0.40 to -0.19] for women and -0.41 METS [-0.44 to -0.38] for men). Cardiorespiratory fitness was positively associated with self-reported physical activity.

Conclusions: Cardiorespiratory fitness in men and women declines at a nonlinear rate that accelerates after 45 years of age. Maintaining a low BMI, being physically active, and not smoking are associated with higher CRF across the adult life span.

Figure 1

Age-related cardiorespiratory fitness (CRF) changes in women and men. Changes are expressed in metabolic equivalents (METs) (A) and as a percentage of peak CRF (B).

Figure 2

Quadratic trends in cardiorespiratory fitness (CRF) for selected body mass index values (BMI; calculated as weight in kilograms divided by height in meters squared) and self-reported physical activity index (PAI). The conditions are defined with linear mixed models (LMM) II, controlling for lifestyle, for women (A) and men (B). An explanation of PAI is given in the “Clinical Examination” subsection of the “Methods” section. Provided for reference are the nonlinear regression line at which lifestyle is not statistically controlled (solid line) and the Aerobics Center Longitudinal Study moderate CRF levels (for women, 7 metabolic equivalents [METs] and for men, 8 METs) associated with higher risk of adverse health outcomes (dashed line).