"This research was prompted by a patient who challenged me to justify my recommendation to anticoagulate her on her 65th birthday," Dr. Husam Abdel-Qadir of Women's College Hospital in Toronto told Reuters Health by email. "She asked me what her risk of stroke would be if she chose not to anticoagulate and whether it would outweigh her risk of bleeding and the inconvenience of the medication."
Although stroke risk increases with age, he said, "there is controversy about the age at which the risk of stroke in someone with AF becomes high enough that it is worthwhile to start blood thinners if they do not have other things that put them at higher stroke risk."
"The American College of Chest Physicians and the Canadian Cardiovascular Society Guidelines state that everyone ages 65 years or older should start a blood thinner," he noted. "In contrast, the American College of Cardiology and the European Society of Cardiology tell practitioners to consider a blood thinner, but do not provide clear guidance on how to do so."
"Importantly," he added, "none of the guidelines distinguish between younger and older people in the 65-74 year old age range - they are all treated the same. They also do not distinguish between the type of blood thinner to use."
"So, we set out to estimate the risk of stroke for patients in this gray zone to help them, and the main finding was that everyone's risk of stroke was NOT high enough to warrant blood thinners," he said.
As reported in JAMA Cardiology, Dr. Abdel-Qadir and colleagues analyzed data on more than 16,000 individuals ages 66 to 74 (median age, 70; 51%, men) who were newly diagnosed with AF in Ontario, Canada, between 2007-2017.
The team assessed the risk of stroke without anticoagulation therapy in those without other CHA2DS2-VASc risk factors (congestive heart failure, hypertension, age 75 or older diabetes, stroke, vascular disease, age 65-74 years, female sex).
A total of 6,314 individuals (38.6%) started anticoagulation therapy during follow-up.
The overall one-year stroke incidence among those who did not receive anticoagulation was 1.1%, and the incidence of death without stroke was 8.1%.
The estimated 1-year stroke risk increased with age from 66 (0.7%) to 74 (1.7%).
The incidence of stroke was not significantly associated with sex.
The authors conclude, "These data suggest that anticoagulation therapy is more likely to benefit older individuals within this group of patients, whereas younger individuals are less likely to gain net clinical benefit from anticoagulation therapy."
Dr. Abdel-Qadir added, "This implies that practitioners should more strongly consider using direct oral anticoagulants (DOACs) as these patients approach 70 years of age. However, the risk of stroke was not high enough to justify the risk and inconvenience of the older and less safe blood thinner, warfarin." Previous research suggests that warfarin benefits patients whose stroke risk exceeds 1.7% per year, and DOACs are likely beneficial when patients' annual stroke risk exceeds 0.9%. (https://bit.ly/3i4EqKm)
Statistician Dr. Laine Thomas of Duke University in Durham, coauthor of a related editorial, told Reuters Health by email, "Abdel-Qadir and colleagues showed that the risk of stroke in one year without anticoagulation more than doubles as age increases from 66 to 74 years. This suggests that the decision to start anticoagulation may be different across this age range."
"To obtain accurate estimates," he said, "studies like this one require sophisticated statistical methods that address the competing risk of death, which precludes stroke, and also to account for the fact that some people chose to start anticoagulation during follow-up."
Dr. Thomas concluded in his editorial that the approach taken by the authors "can serve as a practical guiding example for addressing (these issues) in analogous settings."
SOURCE: https://bit.ly/2ThHZm4 and https://bit.ly/3cjUhkP JAMA Cardiology, online May 19, 2021.
By Marilynn Larkin
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