Experts said that the body water of older individuals tend to decrease with age, from 80 percent in young adulthood to about 55 to 60 percent for people in their 80s. In addition, the temperature sensors in the brain also become less sensitive when people get older. Therefore, senior citizens face a higher risk of dehydration because they may not get the signals to drink enough water during hot days. What's even more dangerous is that elders oftentimes don't feel the typical symptoms of dehydration, such as headache or dizziness but instead they would assume that they're sick or as if they're just feeling bad. Experts added that dehydration can potentially lead to deadly heat stroke, causing muscle cramps, low blood pressure, rapid pulse and nausea. To avoid health hazards caused by the heat, older individuals are advised to drink a quart of water throughout the day, even if one is not thirsty, and try to stay in an air-conditioned room.