STROKE

The word ‘stroke’ is used to describe damage to the brain resulting from lack of blood when arteries burst or become blocked. Like heart disease it is a result of hardening of the arteries and high blood pressure. For more than half a century strokes have been more common in the southeast of the USA than anywhere else in the country. The so-called ‘stroke belt’ comprises a contiguous cluster of states in the southeast, with South Carolina as the focus. High death rates from stroke affect men and women, blacks and whites, with especially high rates in young blacks. High blood pressure is also more common in the ‘stroke belt’. Despite intensive investigations over many years there is no agreed explanation for the existence of the belt. There seems to be no common lifestyle differences that would explain it, and neither do differences in medical care offer an explanation.

There are, however, two clues. The first comes from South Carolina which for decades has had the highest death rates from stroke in the United States, with rates 50% to 60% above the national average. Within the state stroke is most common among people who were born there; it is less common among those born elsewhere in the southeast; and least common in those born outside the southeast. To be part of the stroke belt you have to be born there. This conclusion is supported by findings among black people in New York. As a group they have high death rates from stroke, but these high rates are confined to people who were born in the southern states.

two clues suggest that stroke originates before birthThe second clue to the stroke belt is that within the belt the highest death rates are in people with poor education, low incomes and unskilled occupations. Among affluent people there is no excess of stroke mortality in the southeast, no stroke belt. The two clues suggest that stroke originates before birth, and is therefore linked to mothers, and specifically to mothers from poor backgrounds. There is important new evidence on this. Studies in Helsinki, Finland, show that the mothers of men and women who had high blood pressure and suffered a stroke had small pelvic bones. These are known to be a persisting consequence of undernutrition during infancy, in particular lack of Vitamin D. To understand the US stroke belt we may therefore need to go back to the childhoods of the mothers of people now getting strokes. This is a one century backwards leap to a time when malnutrition was widespread among people living in the stroke belt. The social disruption which began in the Civil War and continued until the depression brought with it food shortages and vitamin deficiencies. The babies of mothers born at this time may have been vulnerable to stroke because the blood vessels in their brains were poorly developed, and weakened with advancing age, bursting or becoming blocked.