A research conducted by the University of Connecticut found that even a loss of 1.5 percent of water from human body can make one feel fatigued and severely affect their mood. Tests conducted on young men revealed that mild dehydration generally affects mental tasks such as memory and vigilance. This is in addition to other effects like fatigue and headaches. Tests on women revealed a higher degree of fatigue and difficulty in concentration. Advanced research on the heat exhaustion has revealed that once dehydration is detected by brain neurons it signals other parts of the brain, thereby regulating mood and affecting mental capabilities.

Via: http://www.medindia.net/news/dehydration-can-alter-peoples-moods-97708-1.htm#ixzz1pLcEuNjV

A study on heat mortality rates in over 40 U.S. cities found that at the onset of summer, the risk of mortality due to heat exhaustion is as high as 5.05 percent, when compared to mid-summer, when the figure is around 2.65 percent. The findings mean that for every 1 degree rise in Fahrenheit the risk of deaths related to heat exhaustion increases by 2.6 percent. 

Via: http://www.medindia.net/news/Beware-of-Early-Summer-Heat-Waves-77512-1.htm#ixzz1pLcUv300

Researchers from Rhode Island Hospital have found out that the three common scales used to asses the level of dehydration in children due to reasons like heat exhaustion, cholera, and diarrhea, are inaccurate and hence unreliable. The scales commonly used are: WHO Scale, the Clinical Dehydration Scale (CDS) and the Gorelick scale. Research is now on to develop clinical scales that are more accurate so that the extent of dehydration can be properly assessed among different age groups.

Via: http://www.medindia.net/news/Dehydration-Levels-in-Children-may-Not-be-Accurately-Estimated-by-Dehydration-Scales-RI-Hospital-93197-1.htm#ixzz1pLcNrABf