I'm 60 and find lower bars to be the best for my back. The tops of my bars are 10cm below the top of my saddle and I spend a fair amount of time in the drops. No back issues whatsoever, even on 100+ mile rides and multiple long days in the saddle. It takes conditioning and core strength built up over time. Everybody is different and this certainly may not work for you, but more upright may not either.