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Atrial fibrillation as an independent risk factor for stroke: the Framingham Study
P A Wolf1, R D Abbott, W B Kannel
1Department of Neurology, Evans Memorial Department of Clinical Research, Boston, Mass.
Insights
Atrial fibrillation significantly increases stroke risk, especially in the elderly, while other cardiovascular conditions have a lesser impact with age. This highlights atrial fibrillation as a key independent stroke risk factor in older adults.
Area of Science:
- Cardiovascular Epidemiology
- Neurology
- Geriatrics
Background:
- Cardiovascular diseases like hypertension and atrial fibrillation are known stroke risk factors.
- The impact of these conditions on stroke incidence may vary with age.
Purpose of the Study:
- To examine the impact of nonrheumatic atrial fibrillation, hypertension, coronary heart disease, and cardiac failure on stroke incidence.
- To assess how these impacts change with advancing age.
Main Methods:
- Analysis of 5,070 participants from the Framingham Study over 34 years.
- Age-adjusted incidence rates and attributable risks were calculated for various cardiovascular conditions.
Main Results:
- Hypertension, coronary heart disease, cardiac failure, and atrial fibrillation all significantly increased stroke incidence.
- The influence of hypertension, coronary heart disease, and cardiac failure on stroke risk decreased with age.
- Atrial fibrillation remained a significant independent stroke risk factor across all ages, with its attributable risk increasing substantially in older adults (80-89 years).
Conclusions:
- Atrial fibrillation is a critical independent predictor of stroke, particularly in the elderly.
- While other cardiovascular conditions' stroke risks diminish with age, atrial fibrillation's impact grows, underscoring its importance in geriatric stroke prevention.
Abstract:
The impact of nonrheumatic atrial fibrillation, hypertension, coronary heart disease, and cardiac failure on stroke incidence was examined in 5,070 participants in the Framingham Study after 34 years of follow-up. Compared with subjects free of these conditions, the age-adjusted incidence of stroke was more than doubled in the presence of coronary heart disease (p less than 0.001) and more than trebled in the presence of hypertension (p less than 0.001). There was a more than fourfold excess of stroke in subjects with cardiac failure (p less than 0.001) and a near fivefold excess when atrial fibrillation was present (p less than 0.001). In persons with coronary heart disease or cardiac failure, atrial fibrillation doubled the stroke risk in men and trebled the risk in women. With increasing age the effects of hypertension, coronary heart disease, and cardiac failure on the risk of stroke became progressively weaker (p less than 0.05). Advancing age, however, did not reduce the significant impact of atrial fibrillation. For persons aged 80-89 years, atrial fibrillation was the sole cardiovascular condition to exert an independent effect on stroke incidence (p less than 0.001). The attributable risk of stroke for all cardiovascular contributors decreased with age except for atrial fibrillation, for which the attributable risk increased significantly (p less than 0.01), rising from 1.5% for those aged 50-59 years to 23.5% for those aged 80-89 years. While these findings highlight the impact of each cardiovascular condition on the risk of stroke, the data suggest that the elderly are particularly vulnerable to stroke when atrial fibrillation is present.(ABSTRACT TRUNCATED AT 250 WORDS)