Although many possible causes for the high stroke incidence have been investigated, the reasons for the phenomenon have not been determined.[citation needed]
Stroke death rates 2002–2007, adults 35+ by US county.
The stroke belt is typically defined to include the states of Alabama, Arkansas, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, and Virginia.[2] In 1980, these 11 states had age-adjusted stroke mortality rates more than 10% above the national average.[3]
Some investigators also consider North Florida to be a part of the stroke belt, based on a stroke mortality rate higher than several states included in the region.[4]East Texas is also characterized as part of the stroke belt.[1]
Analysis by the CDC of U.S. mortality statistics from the period 1991 to 1998 found that for both blacks and whites the counties with the highest stroke death rates were in the southeastern states and the Mississippi Delta region. Stroke death rates for states ranged from a high of 169 per 100,000 in South Carolina to a low of 89 per 100,000 in New York.[7] While most observational studies have focused primarily on stroke incidence in adults, in 2004 researchers reported that children in the eleven stroke belt states also have an increased risk of death from ischemic and hemorrhagic stroke compared with children in other states.[8]
Glymour et al. (2007) reported that adults who had resided in the stroke belt during childhood and had moved outside the region had higher stroke risk at ages 50 and older than adults who grew up in areas with lower stroke incidence.[9] A study reported in 2011 found that people over age 45 living in the eight "stroke belt" states of Alabama, Arkansas, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee had an 18 percent higher incidence of cognitive decline than people in other U.S. regions. Another researcher noted that, "Stroke by itself is a major contributor to cognitive impairment and dementia."[10] Other researchers have made similar observations.[11][12]
In 2011, CDC researchers mapped the occurrence of diabetes in the U.S. by county, finding that highest prevalence of diabetes is in a "diabetes belt" that has extensive overlap with the stroke belt.[13][14]
Black percentage of the population, US Census 2000.
The causes of the elevated incidence of stroke in the stroke belt region have not been determined.[6][9][15][16] Numerous possible contributing factors have been identified, including hypertension, low socioeconomic status, diet, cultural lifestyle, quality of healthcare facilities, smoking, and infections.[17] Among the specific factors that have been proposed or studied are the following:
It has been suggested that the higher stroke death rates in the stroke belt are due to the region's high African American population, because African Americans' stroke death rates are higher than the national average.[18] However, because White people also have higher rates of stroke death in the stroke belt than in other parts of the country, the higher death rates in the stroke belt cannot be attributed solely to the region's higher proportion of African Americans.[3]
In the early 1990s it was hypothesized that selenium deficiency in the soils of the coastal plain might be a causative factor.[19] The subsequent recognition of high stroke incidence in areas with different soil characteristics led researchers to reject this hypothesis.[20]
Inflammation and infection can increase the risk of stroke in a variety of ways,[21] such as by encouraging the process of atherosclerosis.[22] Residents of the Stroke Belt have a higher incidence of sepsis than the general U.S. population,[23] as well as higher levels of C-reactive protein,[24] which is a sign of inflammation in the body.[25]
Some observers have assumed that more stroke belt residents suffer from untreated hypertension. However, researchers have found that residents of the southern United States are as likely to be aware of hypertension and receiving treatment as residents of other U.S. regions.[17] Additionally, researchers who documented the region's elevated incidence of pediatric stroke noted that "If the stroke belt is solely caused by regional differences in atherosclerotic stroke risk factors, it should not apply to children."[8]
It has been suggested that one cause of higher mortality may be the predominantly rural character of the region, which increases the distances that patients must travel to obtain emergency medical treatment.[16] Regional differences in standards of medical care have also been suggested as a contributing factor. In one study, researchers found that patients discharged from hospitals in the stroke belt after suffering acute myocardial infarction were less likely to be treated with warfarin than patients in most other U.S. regions.[26]
Glymour et al. (2007) suggested that the higher stroke incidence in the stroke belt is related to experiences or exposures in childhood.[9]
The same geographical area also has a higher than national average incidence of lung cancer, as it is where much of the tobacco in the United States is grown. Smoking is reputed to be the strongest contributing factor of developing both diseases.[29]
Public health initiatives to reduce stroke incidence in the region[edit]
The U.S. federal government has conducted public health programs specifically aimed at reducing stroke incidence and mortality in the stroke belt. In the 1990s the Stroke Belt Initiative operated in eleven stroke belt states, providing nutrition education, blood pressure screening, smoking cessation programs, weight loss programs, and other health promotion and public education initiatives targeted at stroke risk factors.[3]
In 2004, the Stroke Belt Elimination Initiative of the U.S. Department of Health and Human Services awarded grants aimed at reducing the high incidence of stroke and high rates of stroke death and disability in the seven states with the highest rates of stroke (Alabama, Arkansas, Georgia, Mississippi, North Carolina, South Carolina, and Tennessee).[15]
^IntroductionArchived 2009-11-24 at the Wayback Machine, Atlas of Stroke Mortality: Racial, Ethnic, and Geographic Disparities in the United States (Casper ML, Barnett E, Williams GI Jr., Halverson JA, Braham VE, Greenlund KJ). Atlanta, GA: Department of Health and Human Services, Centers for Disease Control and Prevention, 2003
