EFFECT OF AGING UPON WARFARIN DOSE REQUIREMENTS - A LONGITUDINAL-STUDY

This longitudinal study was designed to establish the rate of age-rela ted change in warfarin dose requirements. Warfarin dosage was recorded retrospectively in 104 patients who had been stabilized on warfarin f or a median period of 10 years (range 6-24 years) for prophylaxis of t hromboembolic disease. There was a significant negative correlation be tween dosage and age at the start of therapy (p = 0.002, r = -0.30). W arfarin requirements fell over time, dosage difference being significa ntly correlated with age difference (p = 0.01, r = 0.25). Use of the r egression equation derived from these data suggests a 21% fall in warf arin requirements in this population over a 15-year period. The relati onship between change in warfarin dose requirements and ageing establi shed in this longitudinal study is in good agreement with that establi shed by cross-sectional studies, suggesting that no major birth cohort effect is influencing requirements in our warfarin-treated population .