Although the magnitude of the association for smoking, atrial fibrillation and left ventricular hypertrophy did not decrease, their importance for stroke risk likely increases with age.
A recently published study in Neurology showed that the known associations of hypertension and diabetes with stroke may decrease with age.1
The magnitude association for stroke was significantly less in patients at older ages with diabetes (HR decreased between ≈2.0 in younger strata and ≈1.3 in older strata). In addition, the magnitude of stroke risk decreased in older patients with heart disease (between ≈2.0 and ≈1.3), and hypertension, at a threshold of 140/90 mmHg (between ≈1.80 and ≈1.50). However, no age-related difference was observed in the magnitude of the association for smoking, atrial fibrillation or left ventricular hypertrophy.
“High blood pressure and diabetes are two important risk factors for stroke that can be managed by medication, decreasing a person’s risk,” lead investigator George Howard, DrPH, professor of biostatistics, University of Alabama at Birmingham School of Public Health, and colleagues said in a statement.2 “Our findings show that their association with stroke risk may be substantially less at older ages, yet other risk factors do not change with age. These differences in risk factors imply that determining whether a person is at high risk for stroke may differ depending on their age.”
The study recruited 28235 stroke-free patients (41% Black, 59% White). between 2003 and 2007 from the REasons for Geographic And Racial Differences in Stroke (REGARDS) cohort study and were followed an average 11 years for incident stroke. Stroke risk factors were assessed by proportional hazards analysis, based on participant baseline age, while Poisson regression analysis assessed associations for participant age change during follow-up. Age stratas 45-64, 65-73, and 74+ years were selected for the proportional hazards analysis; and 45-69, 70-79 and 80+ years for Poisson regression in each analysis.
“It is important to note that our results do not suggest that treatment of high blood pressure and diabetes becomes unimportant in older age,” Howard added in a statement.2 “Such treatments are still very important for a person’s health. But it also may be wise for doctors to focus on managing risk factors such as atrial fibrillation, smoking and left ventricular hypertrophy as people age.”
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Investigators interviewed and physically examined participants at the start of the study to evaluate stroke risk factors. The risk factors for stroke included high blood pressure, diabetes, smoking, atrial fibrillation, heart disease and left ventricular hypertrophy. In addition, race was considered for a risk factor as research has shown that Black patients have a higher risk of stroke than White patients.2 Three age groups were compared, the younger group of patients included ages between 45 and 69, the middle group had ages between late 60s and 70s, then the older group had patients 74 years and older.
Every 6 months, patients followed up to confirm strokes in their medical records. Investigators observed 1405 ischemic strokes among 28235 participants during the median follow-up of 11 years and a total of 276074 person-years exposure.
Patients with diabetes in the younger age group were approximately twice at risk of stroke as patients of similar age without diabetes; whereas patients with diabetes in the older age group had a 30% higher risk for stroke in comparison with patients of similar older age without diabetes. Additionally, the younger age group with high blood pressure had an 80% higher stroke risk than patients of similar age without high blood pressure. Stroke risk decreased to 50% for patients with high blood pressure in the older age group compared with patients of similar age without high blood pressure. A higher risk of stroke was observed in Black patients in the younger age group compared with White patients in the same group. In the older age group, race difference for risk of stroke decreased.
Based on the findings, researchers estimated about 2.0% of patients without high blood pressure had a stroke, compared with 3.6% of patients with high blood pressure in the younger age group. They also estimated that 6.2% of patients with normal blood pressure had a stroke, compared with 9.3% of patients with high blood pressure in the older age group.2 One limitation in the study was the risk factors were only assessed once at the beginning of the study, meaning they might have changed over time.