Tiffany Collinsworth

Cognitive function during acute cold exposure with or without sleep deprivation lasting 53 hours.

INTRODUCTION Cold exposure and sleep deprivation are independently associated with transient cognitive impairment, including difficulty in attention, reaction time, and executive function. The possible interactive effects of cold exposure and sleep deprivation on cognition have not previously been examined. METHODS Six apparently healthy young adult men participated in a within-subjects design with two counterbalanced 53-h protocols: 2-h cold exposure (10 degrees C) blocks every 24 h with normal sleep (Cold), and the same cold exposure in addition to 53 h of complete sleep deprivation (Cold + Sdep). Computerized cognitive tasks of attention, reaction time, and executive function were completed every 4 h during Cold + Sdep, and every 4 waking hours during Cold. RESULTS Cold was associated with a decline in attention over time (b = -0.06). Cold + Sdep was associated with greater attentional decline than Cold (b = -0.13), a significantly reduced speeded/reaction time performance (b = 0.02; b = -0.13), and a trend toward reduced cognitive inhibition over time (b = -0.10). DISCUSSION Findings suggest an additive effect of sleep deprivation to cold exposure in attention and reaction time, and a trend toward this pattern in aspects of executive functioning. These findings raise concern for errors when careful attention and speeded cognitive flexibility are necessary and optimal sleep and protection from the environment is not possible. Mechanisms are not entirely clear, but may be related to transient cerebrovascular or neurochemical changes, or direct physiological effects. Further work is needed to clarify mechanisms for the additive cognitive decline associated with cold exposure and sleep deprivation.

The Influence of Ethnicity on Thermoregulation After Acute Cold Exposure

Abstract Objective.—It is well established that a combination of factors, including ethnicity, may influence an individuals response to cold stress. Previous work from our laboratory has demonstrated that when faced with a cold challenge, there is a similar response in heat production between Caucasian (CAU) and African American (AA) individuals that is accompanied by a differential response in core temperature. The objective of this study was to evaluate the influence of ethnicity (CAU vs AA) on the thermoregulatory response after acute cold exposure (ACE-REC, 25°C air). Methods.—Five AA males (20.8 ± 0.5 years) and 10 CAU males (25.6±4.9 years) underwent pre-experimental testing to determine Vo2max (AA = 37.2 ± 0.1 mL·kg−1·min−1, CAU = 44.3 ± 8.7 mL·kg−1·min−1) and body composition (AA = 14.6 ± 5.4%, CAU = 19.2 ± 5.0%). Participants underwent acute cold exposure that consisted of 120 minutes of exposure to 10°C air (ACE) followed by 120 minutes of recovery in 25°C air (ACE-REC). Rectal temperature (Tre) was measured via a rectal thermistor. Mean skin temperature (Tsk) was assessed with thermistors. Oxygen consumption (Vo2) was assessed via indirect open circuit spirometry. Rectal temperature and Tsk were measured continuously, and if Tre ≤ 35°C, testing was terminated. Results.—Analysis of variance for ACE-REC revealed a significant main effect for Tsk across time (P < .001), Tre across time (P < .001), and Vo2 across time (P < .001). In addition, a significant time × ethnicity interaction was revealed for Tre (P = .008), Tsk (P = .042), and Vo2 (P = .019) during ACE-REC. Conclusions.—Based on these data, there is a differential response between CAU and AA across time for Vo2, Tre, and Tsk ACE-REC.

Increased S100beta is associated with reduced cognitive function in healthy older adults.

Objectives: Vascular pathology is associated with reduced performance on neuropsychological tests, particularly in older adults. A likely explanation involves a disruption in the blood brain barrier (BBB). Work from clinical samples show alterations in BBB function is associated with cognitive dysfunction on testing, though no study has examined this possibility in healthy older adults. Materials and Methods: 35 older adults, without significant neurological or psychiatric history, underwent fasting blood draw and neuropsychological testing. Serum levels of S100β were quantified to provide a measure of BBB function. Results: Partial correlations showed S100β levels were inversely related to performance in multiple cognitive domains, including memory (r = 0.43, p = 0.02), psychomotor speed and visual attention (r = 0.37, p = 0.05), and working memory (r = –0.48, p = 0.008). Conclusions: Findings indicate that increased S100β levels are associated with poorer cognitive function in neurologically healthy older adults, implicating BBB function in age-related cognitive decline. Further work is needed to clarify possible mechanisms, particularly longitudinal studies that involve neuroimaging.