Sex difference in body temperature and thermal perception during nighttime sleep: A time series analysis

Sex differences in body temperature and thermal perception under stable and transient thermal environments: A comparative study

Sex differences in thermal sensitivity and perception: Implications for behavioral and autonomic thermoregulation

BackgroundSex-related differences in human thermal and pain sensitivity are the subject of controversial discussion. The goal of this study in a large number of subjects was to investigate sex differences in thermal and thermal pain perception and the thermal grill illusion (TGI) as a phenomenon reflecting crosstalk between the thermoreceptive and nociceptive systems. The thermal grill illusion is a sensation of strong, but not necessarily painful, heat often preceded by transient cold upon skin contact with spatially interlaced innocuous warm and cool stimuli.MethodsThe TGI was studied in a group of 78 female and 58 male undergraduate students and was evoked by placing the palm of the right hand on the thermal grill (20/40 °C interleaved stimulus). Sex-related thermal perception was investigated by a retrospective analysis of thermal detection and thermal pain threshold data that had been measured in student laboratory courses over 5 years (776 female and 476 male undergraduate students) using the method of quantitative sensory testing (QST). To analyse correlations between thermal pain sensitivity and the TGI, thermal pain threshold and the TGI were determined in a group of 20 female and 20 male undergraduate students.ResultsThe TGI was more pronounced in females than males. Females were more sensitive with respect to thermal detection and thermal pain thresholds. Independent of sex, thermal detection thresholds were dependent on the baseline temperature with a specific progression of an optimum curve for cold detection threshold versus baseline temperature. The distribution of cold pain thresholds was multi-modal and sex-dependent. The more pronounced TGI in females correlated with higher cold sensitivity and cold pain sensitivity in females than in males.ConclusionsOur finding that thermal detection threshold not only differs between the sexes but is also dependent on the baseline temperature reveals a complex processing of “cold” and “warm” inputs in thermal perception. The results of the TGI experiment support the assumption that sex differences in cold-related thermoreception are responsible for sex differences in the TGI.

Four kinds of body temperatures and their relationships with thermal perception

BackgroundPerforming exercise in thermally stressful environments impairs exercise capacity and performance. Cooling during exercise has the potential to attenuate detrimental increases in body temperature and improve exercise capacity and performance.ObjectiveThe objective of this review was to assess the effectiveness of practical cooling strategies applied during continuous exercise in hot environments on body temperature, heart rate, whole body sweat production, rating of perceived exertion (RPE), thermal perception and exercise performance.MethodsElectronic database searches of MEDLINE, SPORTDiscus, Scopus and Physiotherapy Evidence Database (PEDro) were conducted using medical subject headings, indexing terms and keywords. Studies were eligible if participants were defined as ‘healthy’, the exercise task was conducted in an environment ≥25 °C, it used a cooling strategy that would be practical for athletes to use during competition, cooling was applied during a self-paced or fixed-intensity trial, participants exercised continuously, and the study was a randomised controlled trial with the comparator either a thermoneutral equivalent or no cooling. Data for experimental and comparator groups were meta-analysed and expressed as a standardised mean difference and 95 % confidence interval.ResultsFourteen studies including 135 participants met the eligibility criteria. Confidence intervals for meta-analysed data included beneficial and detrimental effects for cooling during exercise on core temperature, mean skin temperature, heart rate and sweat production during fixed-intensity exercise. Cooling benefited RPE and thermal perception during fixed-intensity exercise and improved self-paced exercise performance.ConclusionCooling during fixed-intensity exercise, particularly before a self-paced exercise trial, improves endurance performance in hot environments by benefiting RPE and thermal perception, but does not appear to attenuate increases in body temperature.

Climate change is impacting species globally, with many populations declining at an accelerated rate toward extinction. Ectothermic species are particularly vulnerable given their reproductive success is linked to environmental temperatures. Studies of the effect of temperature on reproductive success in oviparous squamates have focused mostly on nest temperatures, after eggs are deposited. However, in some species gravid females are known to thermoregulate differently than other adults to increase reproductive success. It is essential to understand what influences the thermal biology of breeding adults in a population to implement targeted conservation strategies. The Florida scrub lizard Sceloporus woodi is an endemic species listed as near‐threatened due to decreasing populations. This study is the first to document the thermal biology of these breeding adults in relation to size, sex, and reproductive status. A t test was used to determine whether sexual dimorphism was present in the sampled S. woodi. Full linear mixed‐effects models were used to test the influence of size, sex, and reproductive status on the thermal biology of S. woodi. Despite female‐biased sexual size dimorphism, there were no sex‐based differences in body temperature in the studied population. Interestingly, reproductive status influenced thermal biology of females during the breeding season, with gravid females maintaining lower body temperatures compared to nongravid females. However, gravid females did not regulate their body temperatures more precisely compared to nongravid females. These results indicate the population viability of this endemic species is potentially linked to the different thermoregulatory requirements of gravid females as compared to other adults. Lower body temperatures of gravid females, exacerbated by their lack of thermal precision, have disconcerting conservation implications in the face of climate warming. Future studies focusing on gravid females are warranted to attain effective biodiversity conservation strategies mitigating the impacts of climate warming.

Sexual size dimorphism (SSD) is often assumed to reflect the phenotypic consequences of differential selection operating on each sex. Species that exhibit SSD may also show intersexual differences in other traits, including field-active body temperatures, preferred temperatures, and locomotor performance. For these traits, differences may be correlated with differences in body size or reflect sex-specific trait optima. Male and female Yarrow's spiny lizards, Sceloporus jarrovii, in a population in southeastern Arizona exhibit a difference in body temperature that is unrelated to variation in body size. The observed sexual variation in body temperature may reflect divergence in thermal physiology between the sexes. To test this hypothesis, we measured the preferred body temperatures of male and female lizards when recently fed and fasted. We also estimated the thermal sensitivity of stamina at seven body temperatures. Variation in these traits provided an opportunity to determine whether body size or sex-specific variation unrelated to size shaped their thermal physiology. Female lizards, but not males, preferred a lower body temperature when fasted, and this pattern was unrelated to body size. Larger individuals exhibited greater stamina, but we detected no significant effect of sex on the shape or height of the thermal performance curves. The thermal preference of males and females in a thermal gradient exceeded the optimal temperature for performance in both sexes. Our findings suggest that differences in thermal physiology are both sex- and size-based and that peak performance at low body temperatures may be adaptive given the reproductive cycles of this viviparous species. We consider the implications of our findings for the persistence of S. jarrovii and other montane ectotherms in the face of climate warming.

To examine cardiac function, body temperature and locomotor behaviour in the awake adenosine A(1) receptor knock out mouse of both sexes. Male and female A(1)R (+/+) and (-/-) mice, instrumented with telemetric devices, were recorded during basal conditions and after drug administration. Female mice had higher heart rate, body temperature and locomotion, both during daytime and during the night. Awake A(1)R (-/-) mice had a slightly elevated heart rate, and this was more clear-cut in males. Heart rate was also higher in Langendorff-perfused denervated A(1)R (-/-) hearts. Body temperature was higher in A(1)R (-/-) males and females; locomotor activity was higher in A(1)R (-/-) females, but not in males. The adenosine receptor agonist R-PIA (0.2 mg kg(-1)) decreased heart rate and body temperature, but less in A(1)R (-/-) animals than in A(1)R (+/+) mice (P < 0.001 in both parameters). The unselective adenosine receptor antagonist caffeine had a minor stimulatory effect on heart rate in lower doses, but depressed it at a dose of 75 mg kg(-1). Body temperature was increased after a low dose (7.5 mg kg(-1)) of caffeine in both sexes and genotypes, and markedly reduced after a high dose (75 mg kg(-1)) of caffeine. An intermediary dose of caffeine 30 mg kg(-1) increased or decreased body temperature depending on genotype and sex. Locomotor responses to caffeine were variable depending both on genotype and sex. Thus, the adenosine A(1) receptor is involved in the regulation of heart rate, body temperature and locomotor activity, but the magnitude of the involvement is different in males and females.

Time series analysis is the most commonly used technique for assessing the association between counts of health events over time and exposure to ambient air pollution. Recently, case-crossover analysis has been proposed as an alternative analytical approach. While each technique has its own advantages and disadvantages, there remains considerable uncertainty as to which statistical methodology is preferable for evaluating data of this type. The objective of this paper is to evaluate the performance of different variations of these two procedures using computer simulation. Hospital admission data were generated under realistic models with known parameters permitting estimates based on time series and case-crossover analyses to be compared with these known values. While accurate estimates can be achieved with both methods, both methods require some decisions to be made by the researcher during the course of the analysis. With time series analysis, it is necessary to choose the time span in the LOESS smoothing process, or degrees of freedom when using natural cubic splines. For case-crossover studies using either uni- or bi-directional control selection strategies, the choice of time intervals needs to be made. We prefer the times series approach because the best estimates of risk that can be obtained with time series analysis are more precise than the best estimates based on case-crossover analysis.

Sex differences in physiological responses and thermal perception during repeated extremely cold exposure (−15 °C)

Editorial: Special issue on time series analysis in the biological sciences

Thermal responses and perceptions under distinct ambient temperature and wind conditions

ObjectivesTo investigate the emergence of biological rhythms in the first months of life in human infants, by measuring age-related changes in core body temperature during night-time sleep, hormones (cortisol and...

Variation in metabolism affects energy budgets of individuals and may serve as a mechanism that influences variation at whole organism or population levels. For example, sex differences in metabolic expenditure may contribute to bioenergetic sources of sexual size dimorphism. We measured oxygen consumption rates of 48 western diamondback rattlesnakes (Crotalus atrox) from a sexually dimorphic population and tested the effects of body mass, body temperature and time of day, in three groups of snakes: males, non-reproductive females, and vitellogenic females. Metabolic rates of male and non-reproductive female C. atrox were similar to rates reported for other rattlesnakes (mass exponents ranging from 0.645–0.670). Oxygen consumption was affected by body mass, body temperature and time of day, and was approximately 1.4 times greater in vitellogenic females than in non-reproductive females. No differences were found between males and non-reproductive females. Accordingly, differences in metabolic rate apparently do not contribute directly to sexual dimorphism in this population. Nevertheless, estimates of size-dependent maintenance expenditure lead us to hypothesize that adult female body size may represent a compromise between selection for increased litter size (accomplished by increasing body size), and selection for increased reproductive frequency (accomplished by decreasing body size, and, therefore inactive maintenance expenditure); this is a mechanistic scenario suggested previously for some endotherms.

Thermal relationship between tympanic membrane and hypothalamus in conscious cat and monkey.