Compared with patients who avoided these painkillers, those who took an NSAID had a 2.4-fold higher risk of a major bleed and those who took aspirin had a 1.5-fold higher risk. Even though [this warning about major bleeds with NSAIDS or aspirin] is on the warfarin label. . .
5 years. A decade means 10 years, so to find out how many years are  in half of a decade you would simply divide 10 by 2, which is 5.
A millennium equals 1000 years (the plural is millennia). We calculate the beginning of each millenium in the same way as centuries, so for example, the 3rd millennium BCE includes all of the dates between January 1, 2001 BCE and December 31, 3000 BCE.