Effect of age on international normalized ratio at the time of major bleeding in patients treated with warfarin.
OBJECTIVE
Because the risk of major bleeding associated with warfarin increases with increasing international normalized ratio (INR) as well as with advanced age, we evaluated the association between age and INR in patients with major bleeding events related to anticoagulation with warfarin.


METHODS
Retrospective record review.


METHODS
Two university-affiliated anticoagulation clinics.


METHODS
Sixty-six patients (mean age 61.2 yrs, range 21-90 yrs) receiving warfarin therapy who experienced major bleeding, defined as bleeding requiring hospitalization, during a 20-month index period.


RESULTS
In patients aged 65 years or older, the mean INR at the time of a major bleeding event was significantly lower than that in patients younger than 65 years (INR 3.1 vs 4.2, respectively; p=0.01). For every 1-year increase in age, mean INR at the time of a major bleeding event decreased by 0.03 (p=0.02).


CONCLUSIONS
Patients aged 65 years or older experience warfarin-related major bleeding events at a mean INR 1.1 units lower (95% confidence interval -1.9 to -0.27) than patients younger than 65 years. Older patients may require more aggressive management of overanticoagulation to minimize the risk of major bleeding.
Wittkowsky
Ann K
AK
School of Pharmacy, University of Washington, Seattle, Washington 98195, USA. akwitt@u.washington.edu
Whitely
Kelly S
KS
Devine
Emily Beth
EB
Nutescu
Edith
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced*; D006801:Humans; D019934:International Normalized Ratio; D016014:Linear Models; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D012189:Retrospective Studies; D014859:Warfarin / Q000009:adverse effects*
D014859:Warfarin