Impact of Traditional Stroke Risk Factors on Stroke Risk Lessens Over Time, Study Finds

George Howard, DrPH

An analysis of data from nearly 30,000 adults with more than 275,000 years of follow-up data suggests risk of stroke from traditional risk factors, such as hypertension and diabetes, may decrease as people age.

With support from the National Institute of Neurological Disorders and Stroke and the National Institute on Aging, the analysis of the REGARDS cohort has returned results indicating the impact of these risk factors may decrease over time, such as the relative risk imposed by hypertension decreasing from an 80% increase in risk of stroke for younger patients to a 50% increase in risk of stroke among older patients when compared to their counterparts without hypertension.

“High blood pressure and diabetes are two important risk factors for stroke that can be managed by medication, decreasing a person’s risk,” said lead investigator George Howard, DrPH, of the University of Alabama at Birmingham School of Public Health, in a statement. “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.”

As the population continues to age, a thorough understanding of the differences in relative risk imposed by presence of various risk factors stands to have a substantial impact on risk mitigation as health systems grapple with this aging population. With this in mind, Howard and a team of colleagues from the University of Alabama at Birmingham, launched the current research endeavor with the intent of assessing the impact of hypertension, diabetes, smoking, atrial fibrillation, left ventricular hypertrophy, and cardiovascular disease.

From the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort, investigators identified 28,235 individuals for inclusion in the current analysis. These patients experienced a total of 1405 ischemic stroke events during a follow-up period lasting a median of 11.3 years, with 276,074 person-years of exposure in total.

For the purpose of analysis, investigators estimated associations of stroke risk factors with incident stroke using both proportional hazards analysis based on baseline age of the participants and Poisson regression analysis based on age at exposure. Investigators noted the age groups used in the proportional hazards analysis were defined as 45-64 years, 65-73 years, and 74 years and older while the age groups for Poisson regression were defined as 45-69 years, 70-79 years, and 80 years or older.

In both analytic approaches used in the study, results indicate the magnitude of association with incident stroke was significantly less at older ages for diabetes (hazard or relative risk decreasing from ~2.0 in younger strata to ~1.3 in older strata), heart disease (from ~2.0 to ~1.3), and hypertension defined at a threshold of 140/90 mmHg (from ~1.80 to ~1.50). However, in contrast, no significant age-related differences were observed for magnitude of association for smoking, atrial fibrillation, or left ventricular hypertrophy.

Investigators noted limitations within their study for clinicians to consider before overinterpreting results but pointed out the decreasing magnitude of risk does not mitigate the importance of treating and recognizing these risk factors.

“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. “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.”

This study, “Age-Related Differences in the Role of Risk Factors for Ischemic Stroke,” was published in Neurology.