Stroke incidence has decreased over the last few decades, though studies suggest that most of this decline is in older adults—those over 65 years of age. At least part of the decline is thought to be due to primary prevention via better control of risk factors, including blood pressure. A new study aimed at characterizing trends in the rates of ischemic stroke, published in the journal Stroke, finds that there has been a greater decrease in the risk of stroke among older adults when compared to the decrease in adults at midlife. Previous studies have yielded conflicting results; some show a slight decrease in incidence, while others have suggested an increase in strokes at midlife.1
Decline in stroke risk greatest in older adults
The authors used data from the Framingham Heart Study to compare the 10-year incidence of ischemic stroke over four time periods: 1962 to 1967, 1971 to 1976, 1987 to 1991, and 1998 to 2005. While long-term rates of stroke declined in the entire sample, the decline was greater in older adults compared with younger adults. The researchers found that both age groups showed a long-term decline in stroke risk caused by “traditional vascular factors.”1 For the midlife group, strokes were most commonly categorized as atherosclerotic brain infarction or cardioembolism.
In addition to determining the 10-year incidence of ischemic stroke during each time period, the researchers used the Framingham Stroke Risk Profile, a risk prediction tool that uses multiple variables, to determine how likely the occurrence of stroke is over the next 10 years.1 The results show that at midlife (defined as 35-54 years), the risk of ischemic stroke declined by approximately 39 percent, while the risk of stroke at older age (55 years and older) declined by 53 percent, when comparing the two time periods 1998 to 2005 and 1962 to 1967.1
Risk factors for ischemic stroke also on the decline
In both age groups in the study, the prevalence of most classic risk factors for stroke—hypertension, smoking, and high cholesterol—declined. However, the prevalence of obesity increased across the time periods, and prevalent atrial fibrillation increased in the older adults.1
Looking at previous studies, stroke trends in younger adults have not shown a consistent pattern. While some studies have shown a slight decrease in incidence, others have shown an increase in strokes among this age group. Some of these studies have suggested that vascular risk factors, infective endocarditis, and atrial fibrillation may be on the rise among the younger age group presenting with stroke. One study found that midlife stroke caused by cardioembolism and small vessel occlusion may be on the decline.1
This study may have been limited by the relatively low number of stroke events overall in the midlife group. This may have limited the power of the study to accurately detect a downward trend in this group and contributed to the smaller decrease in the midlife group compared to older adults.1
Newer imaging technology and thrombolytic therapy may contribute to lower stroke incidence
The researchers suggest that the emergence of magnetic resonance imaging (MRI) and the use of thrombolytic therapy for acute stroke “may have led to improved diagnosis of mild or atypical stroke symptoms, especially in younger adults where clinical suspicion for stroke is lower." The authors cite an earlier study which found that since 1993, the number of young adults experiencing their first-ever stroke who received MRI has increased. MRI use increased dramatically during the second half of the time period that the study encompassed.1
To decrease risk of stroke in midlife, more public education about risk factors
Corresponding author Hugo J. Aparicio, MD, MPH, assistant professor of neurology at Boston University School of Medicine, told ScienceDaily that continued preventive efforts, including public health education about risk factors like blood pressure, diabetes, and smoking, are important to decreasing the rate of stroke.
“Our findings demonstrate how continued preventive efforts need to be made to reduce the occurrence of stroke among middle-aged adults,” he said. “Physicians should continue to emphasize to their patients that stroke can occur at any age. Lifestyle choices such as exercise, eating a healthy diet, not smoking, and getting proper sleep likely will reduce the risk of stroke at middle age, just as it does in later life.”2
1. Temporal Trends in Ischemic Stroke Incidence in Younger Adults in the Framingham Study. Stroke. https://www.ahajournals.org/doi/10.1161/STROKEAHA.119.025171 Last accessed October 1, 2019.
2. Long-Term Decline In Stroke Greater In Older Adults: Younger Adults Show Less Steep Decline. ScienceDaily. https://www.sciencedaily.com/releases/2019/05/190516114623.htm Last accessed October 1, 2019.