An investigation into the relationship between age and physiological function in highly active older adults

Abstract

Key points: The relationship between age and physiological function remains poorly defined and there are no physiological markers that can be used to reliably predict the age of an individual. This could be due to a variety of confounding genetic and lifestyle factors, and in particular to ill-defined and low levels of physical activity. This study assessed the relationship between age and a diverse range of physiological functions in a cohort of highly active older individuals (cyclists) aged 55-79 years in whom the effects of lifestyle factors would be ameliorated. Significant associations between age and function were observed for many functions. V̇O2max was most closely associated with age, but even here the variance in age for any given level was high, precluding the clear identification of the age of any individual. The data suggest that the relationship between human ageing and physiological function is highly individualistic and modified by inactivity.

Abstract: Despite extensive research, the relationship between age and physiological function remains poorly characterised and there are currently no reliable markers of human ageing. This is probably due to a number of confounding factors, particularly in studies of a cross-sectional nature. These include inter-subject genetic variation, as well as inter-generational differences in nutrition, healthcare and insufficient levels of physical activity as well as other environmental factors. We have studied a cohort of highly and homogeneously active older male (n = 84) and female (n = 41) cyclists aged 55-79 years who it is proposed represent a model for the study of human ageing free from the majority of confounding factors, especially inactivity. The aim of the study was to identify physiological markers of ageing by assessing the relationship between function and age across a wide range of indices. Each participant underwent a detailed physiological profiling which included measures of cardiovascular, respiratory, neuromuscular, metabolic, endocrine and cognitive functions, bone strength, and health and well-being. Significant associations between age and function were observed for many functions. The maximal rate of oxygen consumption (V̇O2max) showed the closest association with age (r = -0.443 to -0.664; P < 0.001), but even here the variance in age for any given level was high, precluding the clear identification of the age of any individual. The results of this cross-sectional study suggest that even when many confounding variables are removed the relationship between function and healthy ageing is complex and likely to be highly individualistic and that physical activity levels must be taken into account in ageing studies.

Figure 1

Maximal aerobic capacity relationships with age The relationship of age with maximal aerobic capacity (in absolute terms, A; relative to body weight, B; and fat free mass (FFM)) and maximum heart rate (D). Data are displayed on scatterplots (A–D) and graphs of functional equivalence (E–H). Data are from females (• and continuous line) and males (∇ and dashed line).

Figure 2

Ventialtory threshold and O₂ uptake kinetics relationship with age Ventilatory threshold (A–D) and O₂ uptake kinetics (E) with age. Data are from females (• and continuous line) and males (∇ and dashed line).

Figure 3

Relationship of skeletal muscle mass index and bone strength with age Relationship between skeletal muscle mass index (SMI, A), whole body (B), hip (C) and lumbar spine (D) bone mineral density (BMD) with age. Data are from females (• and continuous line) and males (∇ and dashed line).

Figure 4

Relationship between age and hormone levels Relationship between age and cortisol, DHEAS, testosterone and IGF-1 levels. Data are from females (•) and males (∇).

Figure 5

Relationship between cardiovascular function and age Relationship between cardiovascular (A–C) and lung (D–G) function with age. BP; blood pressure; PEF, peak expiratory flow rate; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity. Data are from females (• and continuous line) and males (∇ and dashed line).

Figure 6

Neuromuscular function associations with age Relationship between age and neuromuscular function. NCV, nerve conduction velocity; rms, root mean square; AP, anterior–posterior; ML, medio-lateral; EC, eyes closed; TUG, timed up and go. Data are from females (• and continuous line) and males (∇ and dashed line).