Handle bar risers

[fyresword]

I've seen a few posts on here about handle bar risers so I'm just wondering what the advantages disadvantages are? If my height makes any difference I'm 6'2", just wondering if they would be any point in me getting any as on long journeys I do get a bit of pain in my lower back (although this could be down to kevlar stuff and not riding position as my jacket is a little on the short side when on the bike, and before you say I know I need to change it

D