Wear and tear are caused not only by changes in function but also by repeated fluctuations of various physiological systems and/or long-term exposure to elevated levels of physiological activity.
Homeostasis: emphasis is on steady state and optimal set points
Allostasis: emphsis is on optimal operating ranges of physiological systems
Allostatic Load: stability through change represents the cumulative, multi-system view of physiological toll that may be exacted on the body through attempts at adaptation.
An organism must vary all parameters of its internal milieu and match them appropriately to environmental demands.
Charlson, M.E., Pompei, E., Ales, K.L. & MacKenzie, C.R. A new method of classifying prognostic co-morbidity in longitudinal studies, development and validation.
J. Chronic Disease, 40: 373-383, 1987
Best of comprehensive indices of physiological competence:
Seeman, T.E., Singer, B.H., Rowe, J.W., Horwitz, R.I. & McEwen, B.S. Price of adaptation-Allostatic load and its health consequences.
Arch. Intern. Med., 157: 2259-2268k, 1997.
1,2. Systolic & diastolic blood pressure (indices of cardiovascular activity)
3. Waist-hip ratio (index of long-term metabolic/lipid deposition)
4,5. Serum HDL and total cholesterol levels (indices of artherosclerotic risk)
6. Blood plasma levels of total glycosylated hemoglobin (iondex of glucose metabolism)
7. Serum dehydroepiandrosterone sulfate levels (index of hypothalamo-pituitary-adrneal [HPA] inhibitor/antagonist)
8. 12-hour urinary cortisol excretion (index of12 hour integrated HPA activity)
9,10. 12-hour urinary norepinephrine & epinephreine excretion levels (index of 12-hr integrated sympathetic activity).
*Systolic blood pressure at risk: > 148mmHg
*Diastolic blood pressure at risk: > 83mmHg
*Waist-hip ratio at risk: > 0.94
Total cholesterol-High Density Lipoprotein (HDL) ratio at risk: > 5.9
Total glycosylated hemoglobin level at risk: > 7.1%
Urinary cortisol level at risk: > 25.7 mg/g creatinine
Urinary epinephrine level at risk: > 5 mg/g creatinine
Urinary norepinephrine level at risk: > 48 mg/g creatinine
*HDL cholesterol level at risk: > 1.45 mmol/L or greater than or equal to 56 mg/dL
*DHEA (Dehydroepiandrosterone) level at risk: > 2.5 micro-molar/L or > 910 ng/mL
Relationship between increased allostatic load and risk of decline in physical performance: greater risk with increased severity of the allostatic load
Relationship between incidence of cardiovascular disease and allostatic load: increased incidence of cardiovascular disease with increased severity of the allostatic load
Relationship between increased allostatic load and increased risk for decline in memory: increased risk for decline in memory with increased severity of the allostatic load