My mother-in-law has arthritis in her hands, and couldn't use the deore thumb shifters anymore. Pushing against the lower thumb shifter caused her a lot of pain. So I upgraded her to drop bars/105 shifters (5700), this meant using the full hand of fingers to change gear, regardless of going up or down. No more thumb problems, and she can shift gears easily, no problem.
Other wise, look at gripshifters. But the only decent ones about are Sram X9 (I believe?)