There were no significant differences in primary outcomes between the caffeine group and the placebo ( adjusted mean difference of -@ -LSB- @ % confidence interval ( CI ) = -@ to @ min -RSB- ; P = @ for actigraphic total sleep time ; and adjusted rate ratio -LSB- caffeine/placebo -RSB- for apnea-hypopnea index of @ -LSB- @ % CI = @-@ @ -RSB- ; P = @ ) .