Postural stability and neurobehavioural effects of heat exhaustion among adult men.

The medical complications of heat disorders, including haematological, cardiovascular and renal damage, have been well documented. However, very little has been written on its neurological complications. The objective of this study was to assess the effects of heat exhaustion on postural stability and neurobehavioral functions of men. The study is prospective in design and spans a 3-year period. All soldiers who were diagnosed to have heat exhaustion (cases) from 1 March 1998 to 31 August 1998 were included in the study. For each case, a healthy soldier (matched for age, ethnicity, years of education and military vocation) was recruited to serve as control. Each subject had a neurobehavioral assessment by using the Swedish Performance Evaluation System (SPES), a computerized test battery. The postural stability of the subjects was assessed using a computerized postural sway system. Findings for 37 heat exhaustion cases and 37 controls revealed that cases had a significantly higher prevalence of neurasthenia symptoms compared to the controls. There were significant (small) differences between the cases and controls in the neurobehavioral tests of choice reaction time, digit span and some parts of colour word stress and logical series measures. Postural stability in the cases was significantly poorer when in the "eyes-closed" condition, compared with the controls. Men with heat exhaustion, studied 2 weeks after the acute episode, had significantly more symptoms of neurasthenia, poorer performance in short-term memory and slower reaction time. The cases (as a group) had significantly poorer postural stability.