The drink has also aroused criticism for its use of caffeine, which can cause physical dependence (caffeine dependence),[21] and can reduce sleep quality.[22] A link has been shown between long-term regular cola intake and osteoporosis in older women (but not men).[23] This was thought to be due to the presence of phosphoric acid, and the risk for women was found to be greater for sugared and caffeinated colas than diet and decaffeinated variants, with a higher intake of cola correlating with lower bone density.