Does dehydration affect focus, and do electrolytes help?

Dehydration lowers mental performance a little. A 2018 review of 33 studies found small losses in thinking (cognition), mostly in attention, planning and coordination. The losses were larger when people lost more than 2% of body weight as water.^[1] In a trial at 30 °C, water with an electrolyte capsule tended to protect mood best, but the colour of the drink also had an effect.^[2]