Table 3.

Number of person years' treatment needed to produce one excess case of serious upper gastrointestinal bleeding. Estimates are based on data for people aged 50 or above

Exposure	Total drug exposure in background population (person years)	NNTH: person years−1 (95% CI)
Aspirin alone	40 599	1040 (725 to 1641)
Clopidogrel alone	2 391	8800 (NNTH 723 to ∞; NNTB 1832 to ∞)
VKA alone	13 205	985 (550 to 2372)
Dipyridamole alone	8 007	873 (445 to 2557)
Aspirin and clopidogrel	739	124 (54 to 312)
Aspirin and VKA	1 213	184 (93 to 407)
Dipyridamole and aspirin	7 713	595 (348 to 1201)

NNTB=number needed to treat for one patient to benefit; NNTH=number needed to treat for one patient to be harmed; VKA=vitamin K antagonist.