Abstract P396: The Stroke Belt: Forged in the Heat of the Buckle? A Hypothesis

Abstract

The “stroke belt”(SB) in the SE USA has significantly higher stroke rates in whites (W) and African Americans (AA). HTN is the major driving force. The “Buckle” (B) of the SB, with even higher rates, lies along the costal “low country” plains of the Carolinas. Being born in the B is a powerful exposure that increases risk. Forty percent of all US slaves came thru, slaved and many died in the B of the SB. While reading the scholarly review “Slavery, Disease and Suffering in the Southern Low Country”, by Dr. Peter McCandless, (Cambridge U Press, 2011) I was stuck with the effect of the hot, humid weather with morbidity and mortality in the B. He details three decimating “fevers”. The first two, Malaria and Yellow Fever, are known to have left their mark on the human genome. The third fever, “Malignant Fever” (MF), coined by James Lind in “An Essay on Diseases Incidental to Europeans in Hot Climates” (London, 1768). MF was characterized as a fever of sudden onset resulting in rapid death in a few days. Lind describes MF morality in sailors “wooding” onshore during hot days who died overnight if they failed to return to the “cleaner air” of the ship. Many new arrivals, including military forces, to the SB/B succumbed to MF in days. Especially in the summer. Treatment of MF was removal to an area of “healthier air”/high country which quickly “cured” MF. I suggest this lowered the heat index, improving survival in heat illness/stroke or “Malignant fever”. In addition, an affliction called the “Dry Agues” characterized by muscle spasms, weakness and physical and mental fatigue was a major cause of disability during the summer. I interpret this as the classic features of hypokalemia driven by Na/K losses during heat adaptation and modulated by intakes of Na, K and the RAAS. As death from terminal heat stoke manifests as yellow skin/bleeding diathesis many of these deaths were likely wrongly attributed to Yellow Fever. Recent US military research documents a lower susceptibility to heat injury in both Ws and AAs from the SB/B. As the genes sing the songs of survival, I propose that selective survival, related to heat illnesses, plays a role in today’s greater prevalence of HTN in Ws and AAs in the SB and its B. Study of family trees, their genes and the physiology of heat control systems should be informative.