Hypernatremia caused by decreased water intake is seen in which groups?

• A. Old
• B. Infant
• C. Both old and infant
• D. Athletes

Answer: (C)

Hypernatremia from a water deficit happens when free water intake is not enough to balance bodily water losses, causing plasma osmolality to rise and cells to shrink. The groups most at risk are those who cannot reliably regulate or obtain fluids: elderly individuals and infants. In the elderly, the thirst sensation often diminishes with age, and cognitive decline or dependence on others can prevent adequate fluid intake; medications and illnesses can also worsen the balance. In infants, there is no self-regulation of intake—their fluids depend entirely on caregivers—and they have relatively higher insensible water losses with immature kidneys that don’t concentrate urine as efficiently. Because of these factors, decreased water intake leading to hypernatremia is commonly seen in both older adults and infants.