[Dose-response of aspirin on platelet function in very elderly patients]

Area of Science:

• Geriatric Medicine
• Cardiovascular Pharmacology
• Hematology

Background:

• Aspirin is widely used for cardiovascular prevention, but optimal dosage in very elderly patients remains debated.
• High-dose aspirin (100 mg/d) can increase bleeding risk, particularly in older populations.
• Individual variability in platelet aggregation response to aspirin necessitates personalized dosage considerations.

Purpose of the Study:

• To evaluate the impact of switching from 100 mg/d to 40 mg/d aspirin on cardiovascular benefit, bleeding risk, and platelet aggregation.
• To assess the safety and efficacy of a lower aspirin dosage in very elderly individuals.
• To understand the relationship between aspirin dosage, platelet function, and gastrointestinal outcomes in octogenarians.

Main Methods:

• A cohort of 537 very elderly patients (≥80 years) on 100 mg/d aspirin had their arachidonic acid-induced platelet aggregation (AA-Ag) measured.
• A subgroup of 100 patients with low on-treatment platelet aggregation, high bleeding risk, and low cardiovascular event risk were switched to 40 mg/d aspirin.
• Platelet aggregation, bleeding events, and upper gastrointestinal symptoms were monitored for 3 months post-switch.

Main Results:

• Aspirin 100 mg/d showed heterogeneous AA-Ag (0.42%-28.78%); 71% of patients had low on-treatment platelet aggregation.
• Switching to 40 mg/d aspirin increased AA-Ag to 11.21%±4.95%, with 15% having low platelet aggregation.
• The 40 mg/d group experienced a decrease in gastrointestinal bleeding (12% to 5%) and upper gastrointestinal symptoms (59% to 21%).

Conclusions:

• Lowering aspirin dosage from 100 mg/d to 40 mg/d in very elderly patients significantly reduces bleeding events and improves gastrointestinal symptoms.
• The 40 mg/d dose effectively inhibits platelet aggregation, though with increased variability compared to 100 mg/d.
• This dosage adjustment offers a potential strategy for optimizing aspirin therapy in high-risk elderly individuals, balancing efficacy and safety.