Biomedical Engineering Reference
In-Depth Information
Figure 7
. The physiologic basis of frailty. Multiple interacting physiologic inputs (top) pro-
duce highly irregular, complex dynamics (middle), which impart a high level of functionality
(bottom) on an organism. As the inputs and their connections degrade, the output signal be-
comes more regular and less complex, resulting in functional decline. Ultimately, with contin-
ued loss of physiologic complexity, function may fall to the critical level below which
an organism can no longer adapt to stress (the frailty threshold). Reprinted with permission
from (2).
7.
CONCLUSION
In conclusion, aging results in a number of changes in anatomic structures
and physiologic control processes that result in a reduction in system complexity
and a loss of ability to adapt to common stresses in the external and internal en-
vironment. This loss of complexity may be the physiologic basis of frailty. New
interventions aimed at restoring complex dynamics may be able to enhance
physiologic adaptation and prevent the onset of disease and disability.
8.
ACKNOWLEDGMENTS
This work was supported by Grants AG04390 and AG08812 from the Na-
tional Institute on Aging, Bethesda, Maryland. Dr. Lipsitz holds the Irving and
