My wife was having wrist and shoulder issues when we went to Seattle to pick up a tandem last summer (she rides captain). At the last minute, she mentioned this to the shop owner. He told her he had the same issues and had some success by changing to carbon bars. She figured $300 was a lot less than the medical costs she might be looking at, so it was worth a try. The next day, we got on the bike and rode 450 miles home over the weekend. She didn't have any issues at all and credits the bars. She used to put all sorts of padding on the bars, but is happy with just a bit of cloth tape on the carbon bars. (By the way, we run 26X1.25 tires, which is approximately 32mm wide)
I just picked up a pair for half that price on Chainlove for our other tandem. Maybe I'll put some on for me when I find a wide enough set on sale.