The primary outcome ( ESS ) improved more on modafinil than placebo ( 3.6 points , 95 % CI 1.3 to 5.8 , p = 0.003 ) and the secondary outcome ( 40-min driving simulator performance ) also improved more on modafinil than placebo ( steering deviation 4.7 cm , 95 % CI 0.8 to 8.5 , p = 0.018 ) .