History of heatstroke – lessons from the workplace
Zachary J. Schlader, PhD, FACSM
In many ways the history of understanding the human body’s responses to exposure to hot environments, often termed heat stress, is founded on observations in the workplace. Arguably, this work started with observations of the regular occurrence of sunstroke in South African gold miners in the late 18th and early 19th centuries. Sunstroke, now known as heatstroke, is the most severe form of heat illness and is described by extreme elevations in internal body temperature and nervous system alterations (including confusion, coma, disorientation). When diagnosis and/or treatment is delayed, heatstroke is often deadly or can cause long-term health challenges. Equally, if not more, important is that observations in the workplace led to the development of strategies to prevent heatstroke. For example, in the South African mines, adaptations caused by repeated exposure to heat, known as heat acclimation, were shown to reduce the incidence of heatstroke in gold miners.
Similarly, observations in the early 19th century with the building of the Hoover Dam in the Mojave Desert in North America highlighted the importance of hydration and supplementation with electrolytes (to offset losses due to prolonged sweating) for optimal functioning during manual labor under heat stress. Indeed, scientific reports from that time documented the profuse loss of electrolytes due to prolonged sweating. Based on these observations, accounts from the 1930’s suggest that a posting in the onsite cafeteria encouraging water and salt intake reduced the occurrence of heatstroke from thirteen in a year to zero the following year.
We know now that fluid and electrolyte replacement is not an effective treatment for heatstroke. Rather, heatstroke should be treated with rapid cooling. That said, maintaining good hydration practices by regularly drinking water, or a beverage containing electrolytes if the work is prolonged, reduces the risk of heatstroke. This is likely because dehydration can cause greater increases in internal body temperature during heat stress compared to when someone is well hydrated. Recent data also show that adequate hydration with an electrolyte beverage before heat stress reduces the severity of organ injury following heatstroke, compared to drinking water. Thus, good hydration practices can reduce the risk of heatstroke, while additional data support that hydration with an electrolyte containing beverage may also have additional health benefits in the workplace.
Lessons learned: With increased heat exposure there is a heightened risk of developing heat illness, including heatstroke. Workers regularly exposed to hot environments take most of the burden of the adverse health effects of heat stress. Historical observations in the workplace have provided important insights into the health challenges of working in the heat. These observations indicate that good hydration practices, including drinking electrolyte containing beverages when work is prolonged, are an important part of the healthy work environment.