Caffeine extends worm life span at 15°C and 20°C. (A) Caffeine concentrations in the 5 to 20 mM range increase life span at 15°C. (B) Caffeine concentrations in the 0.5 to 10 mM range increase life span at 20°C. (C) Caffeine dose response curves reveal optimal concentrations for increased life span. *P < 0.05 vs. 0 mM at the same temperature.