When we are parched or dehydrated, we tend to have an increased thirst reflex, which prompts us to drink more water. This is coordinated by the cells monitoring intracellular and extracellular water concentrations.

When water losses exceed water intake, regulatory hormones are stimulated to increase the thirst reflex. In the brain, antidiuretic hormone (ADH) is then excreted, which increases the sense of thirst.

ADH also stimulates the kidneys to reabsorb more water and make less urine. This is a crucial mechanism during times of water deficiency.

Unfortunately, elderly people often have a dysregulated thirst reflex, meaning that they’re not increasing production of ADH levels when they are dehydrated. As a result, they don’t get the stimulus to drink more. For this reason (among others), dehydration is very common in the elderly.

As a result, water intake by older individuals needs to be monitored closely.