IN “REGARDS” TO THE STROKE BELT
A stroke is a sudden interruption of blood to the brain, caused by a clogged or ruptured blood vessel. There are two main types of strokes: ischemic stroke is caused by a blockage, usually a clot, in the artery of the brain. Less commonly, a hemorrhagic stroke results from a head injury or an aneurysm, or ballooning of the blood vessel wall. It can manifest itself as sudden, unexplained numbness or tingling, especially on one side of the body, slurred speech, blurred vision, dizziness, confusion, fainting, and severe unexplained headache. Approximately 800,000 Americans suffer a stroke every year with over 130,000 dying from it. There are some clusters of strokes in the US with increased prevalence in certain regions – this is called the stroke belt.
What is the definition of the Stroke Belt?
The higher stroke mortality rate in the Southeastern United States has been noted for over 50 years and in the mid-1970s, this region was referred to as the Stroke Belt. The CDC reports the stroke mortality rates in the Southeastern US to be two to four times higher than in other regions. At the state level, these include North Carolina, South Carolina, Georgia, Tennessee, Alabama, Mississippi, Arkansas, and Louisiana. These States have an age-adjusted rate of stroke mortality of at least 10% above the national average. The incidence of stroke has continued to rise over the past 20 yrs but the age-adjusted stroke mortality has declined significantly. Nevertheless, the geographic disparity persists with mortality still in excess of 27% in the Stroke Belt relative to other regions.
What is the “REGARDS” Study?
“REGARDS” is an abbreviation for REasons for Geographic And Racial Difference in Stroke. It is an observational study of risk factors for stroke in adults 45 years or older. It is co-sponsored by the National Institute of Neurological Disorders and Stroke and the National Institute on Aging. It recruited 30,239 participants between 2003 and 2007. They completed a telephone interview followed by an in-home physical examination. Measurements included risk factors such as blood pressure and cholesterol levels and an ECG. At six-month intervals, participants are called and asked about stroke symptoms, hospitalizations, and health status. The study involves the careful follow-up of people from all different regions of the US with 56% coming from the Stroke Belt, 42% Black, and 55% women. It is designed to root out the cause of vascular disease including stroke and potentially lead to the prevention of stroke.
What are the contributing factors to the Stroke Belt?
The Stroke Belt has a higher proportion of non-Hispanic black residents (26%) compared to the rest of the US (10%). Despite the fact that the excess mortality in the Stroke Belt had declined to 25% for blacks in the last decade, it remains in excess of 20% compared to white. It is unclear whether this is related to a higher prevalence of risk factors or other social determinants of health prevalent in the Stroke Belt.
Reports have shown a higher prevalence of hypertension and diabetes mellitus in the Stroke Belt. The prevalence of cigarette smoking is second highest in the Midwest at 16.9%. These factors certainly could contribute to the higher stroke mortality in the Stroke Belt.
Inflammation and Infections are recognized risk factors for stroke and are more prevalent in the Stroke Belt. Residents in the Stroke Belt have been shown to have a higher adjusted risk of sepsis. A higher level of inflammation as measured by CRP (C-reactive protein) and IL-6 (interleukin-6) has been documented in the Stroke Belt and its relation to social determinants of health and contribution to higher stroke mortality are being investigated.
Another contributing factor is the poorer dietary intake in the region. The southern dietary pattern includes a high intake of fried foods, organ meat, processed meat, egg dishes, high-fat dairy foods, sugar-sweetened beverages, and bread. This dietary pattern has been associated with a 39% increase in stroke risk. Interestingly, this dietary pattern is not geographically different in the Stroke Belt compared to the rest of the US. Several studies have documented the benefits of the Mediterranean dietary pattern with a 15-25% reduction in the incidence of stroke. This pattern was seen in 25% of residents in the Stroke Belt and was not different from other regions.
Physical activity has been shown to reduce the risk of stroke by 25% and stroke mortality by 17% with some differences by sex and degree of activity. REGARDS demonstrated that inactive people had a 20% higher risk of stroke. However, there was no difference in the level of activity reported in the Stroke Belt compared to other regions with 30% of residents exercising >4 times per week, 36% exercising 1-3 times per week and 33% not exercising at all.
The influence of socioeconomic status on stroke risk and outcomes has been well documented. The unemployment rate, percent of the population with a high school or lower education level, and proportion of the population in poverty have been correlated with stroke mortality. It is difficult to differentiate between the effects of social determinants of health and the higher prevalence of stroke risk factors among individuals with lower socioeconomic status.
Other factors such as depression, stress, discrimination, and genetics remained under investigation. Other factors such as regional disparity and access to care and quality of care should be considered in future studies.