Dehydration increases neural activity, meaning that the brain is working harder than usual to perform a task. Additionally, dehydration can lead to volume changes in the brain and brain ventricles. Dehydration in older people is considered a common occurrence. It has been reported that between 17 and 28 percent of older adults are dehydrated; it is also frequently a reason for admission to the hospital. One study showed the issue is diagnosed in 8.9 percent of hospitalized patients over the age of 65.