Age and systemic acid-base equilibrium: analysis of published data.
To investigate whether systemic acid-base equilibrium changes with aging in normal adult humans, we reviewed published articles reporting the acid-base composition of arterial, arterialized venous, or capillary blood in age-identified healthy subjects. We extracted or calculated blood hydrogen ion concentration ([H+]), plasma bicarbonate concentration ([HCO3(-)]), blood PCO2, and age, and computed a total of 61 age-group means, distributed among eight 10-year intervals from age 20 to 100 years. Using linear regression analysis, we found that with increasing age, there is a significant increase in the steady-state blood [H+] (p < .001), and reduction in steady-state plasma [HCO3(-)] (p < .001), indicative of a progressively worsening low-level metabolic acidosis. Blood PCO2 decreased with age (p < .05), in keeping with the expected respiratory adaptation to metabolic acidosis. Such age-related increasing metabolic acidosis may reflect in part the normal decline of renal function with increasing age. The role of age-related metabolic acidosis in the pathogenesis of the degenerative diseases of aging warrants consideration.
Department of Medicine, University of California, San Francisco.
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D000136:Acid-Base Equilibrium / Q000502:physiology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D004032:Diet; D005260:Female; D006706:Homeostasis; D006801:Humans; D007668:Kidney / Q000502:physiology; D008297:Male; D008875:Middle Aged