Figure 6. The cumulative loss of reserve over time functions leads to increasing organismal vulnerability.

Increasing molecular and cellular disorder as we age leads to loss of tissue organ and system reserve functions. A. The rate of increased vulnerability of reserve in our various functions (thin lines) is variable, and not always monotonic but sometimes biphasic or oscillatory due to compensatory mechanisms that occur among functions. The eigen vector for loss of reserve function, however (thick arrows), progressively increases with advancing adult age and underlies phenomena presently referred to as diseases and “frailty”, or the inability to perform normal activity of daily living. The lines are arbitrary functions that decline at arbitrary rates. B. The cumulative loss of our reserve functions over time leads to age-associated increasing vulnerability to diseases and frailty from which we were protected at earlier ages.