Altered water excretion in healthy elderly men

Area of Science:

• Nephrology
• Gerontology
• Endocrinology

Background:

• Aging is associated with physiological changes affecting fluid balance.
• Kidney function, including glomerular filtration rate (GFR), typically declines with age.
• Understanding age-related differences in water handling is crucial for maintaining health in older adults.

Purpose of the Study:

• To investigate the renal and vasopressin (AVP) response to an oral water load in healthy elderly men.
• To compare water excretion capacity in elderly men versus young healthy volunteers (both water-replete and water-deprived).
• To determine the role of reduced glomerular filtration rate in age-related water excretion impairment.

Main Methods:

• A standard oral water load (20 ml/kg) was administered to elderly men and two groups of young volunteers.
• Urine output, diuresis, free-water clearance, and plasma AVP levels were measured over time.
• Creatinine clearance (Ccr) was assessed to adjust for differences in kidney function.

Main Results:

• Elderly men excreted significantly less water (41%) compared to water-replete (100.7%) and water-deprived (70%) young adults within 2 hours.
• Peak diuresis and free-water clearance were significantly lower and delayed in the elderly group.
• After adjusting for reduced creatinine clearance, the differences in water excretion indices between young and old groups were no longer significant.
• Plasma AVP levels decreased similarly in all groups, with no significant differences between age groups.

Conclusions:

• Healthy elderly men exhibit an impaired ability to promptly excrete excess water.
• This impairment is partly attributed to an age-related reduction in glomerular filtration rate.
• Fluid balance regulation in the elderly may be compromised by age-associated decreases in kidney function.