Combined Effects of Cold Exposure and 53 Hours of Sleep Deprivation on a Sustained Attention Task

INTRODUCTION It is well documented that sleep deprivation has a negative impact on cognitive performance (Durmer & Dinges 2005). Research also suggests that individuals typically need seven hours of sleep to maintain normal physiological function (Armstrong 2000). While the effects of sleep deprivation are well documented its interaction with acute cold exposure is still unclear. The relationship between sleep deprivation and thermoregulation has only recently come into focus. Castellani et al. (2003) examined shifts in body temperature threshold as a result of numerous detrimental factors (i.e., negative energy balance, sustained activity and sleep loss). They reported that during cold exposure following 84 hours of sustained operations, thermoregulatory variables including metabolic heat production, shivering threshold, respiratory exchange ratio and core temperature, were all lower than those exhibited during the control trial. Young et al. (1998) also utilized multiple stressors (i.e., negative energy balance, sleep deprivation and exertional fatigue) to examine soldiers’ ability to thermoregulate in a cold environment. They found that thermal sensation was more pronounced (soldiers felt colder) immediately following 61 days of military training as opposed to the recovery cold exposure trials (48 hours and 109 days post-training). Additionally, the acute affects of sleep deprivation were documented by a significant decrease in rectal temperature during the cold exposure following the training and to a lesser extent following 48 hours of recovery (Young et al. 1998). More recently, Caine-Bish et al. (2005) examined the effects of acute cold exposure, following 33 hours of sleep deprivation, on hormone concentrations and metabolic rate. In contrast to Castellani et al. (2003) and Young et al. (1998) they observed no change in rectal and skin temperatures, heat production and thermal sensation due to sleep deprivation. To date, little research has focused on the effects of sleep deprivation (> 36 hrs) in conjunction with acute cold exposure on cognitive function. Consequently, this study evaluated the cognitive impact of a repeated two hr cold challenge during 53 hrs without sleep.