The number of actinic keratoses was 11 % lower in the nicotinamide group than in the placebo group at 3 months ( P = 0.01 ) , 14 % lower at 6 months ( P < 0.001 ) , 20 % lower at 9 months ( P < 0.001 ) , and 13 % lower at 12 months ( P = 0.001 ) .