Influence of different light intensities during the daytime on evening dressing behavior in the cold

Objective Measures of Immediate “Energizing” Effect of Light: Studies Review and Data Analysis

While the energizing effect of light has been known since the early years of light therapy, its reliable detection using objective measures is still not well-established. This review aims to ascertain the immediate energizing effect of light and determine its best indicators. Sixty-four articles published before July 2022 were included in the review. The articles described 72 (sub-)studies performed in healthy individuals. Fourteen measures were analyzed. The analysis showed that light causes an energizing effect that can be best documented by measuring core (rectal) body temperature: the proportion of the studies revealing increasing, unchanging, and decreasing rectal temperature was 13/6/1. The second most suitable indicator was heart rate (10/22/1), which showed concordant changes with rectal temperature (a trend, seven mutual studies). There is no evidence from the reviewed articles that oxygen consumption, skin conductance, blood pressure, heart rate variability, non-rectal inner temperature (combined digestive, tympanic, and oral), skin temperature, or cortisol levels can provide light effect detection. Four other measures were found to be unsuitable as well but with less certainty due to the low number of studies (≤3): skin blood flow, noradrenaline, salivary alpha-amylase, and thyroid-stimulating hormone levels. On the other hand, light exposure had a noticeable effect on sympathetic nerve activity measured using microneurography; however, this measure can be accepted as a marker only tentatively as it was employed in a single study. The analysis took into account three factors—study limitation in design/analysis, use of light in day- or nighttime, and relative brightness of the light stimulus—that were found to significantly influence some of the analyzed variables. The review indicates that the energizing effect of light in humans can be reliably detected using rectal temperature and heart rate.

Does thermal control improve visual satisfaction? Interactions between occupants' self-perceived control, visual, thermal, and overall satisfaction

Occupants' satisfaction had been researched independently related to thermal and visual stimuli for many decades showing among others the influence of self-perceived control. Few studies revealed interactions between thermal and visual stimuli affecting occupant satisfaction. In addition, studies including interactions between thermal and visual stimuli are lacking different control scenarios. This study focused on the effects of thermal and visual factors, their interaction, seasonal influences, and the degree of self-perceived control on overall, thermal, and visual satisfaction. A repeated-measures laboratory study with 61 participants running over two years and a total of 986 participant sessions was conducted. Mixed model analyses with overall satisfaction as outcome variable revealed that thermal satisfaction and visual satisfaction are the most important predictors for overall satisfaction with the indoor environment. Self-perceived thermal control served as moderator between thermal satisfaction and overall satisfaction. Season had slight influence on overall satisfaction. Random effects explained the highest amount of variance, indicating that intra- and interindividual differences in the ratings of satisfaction are more prevalent than study condition. Future building design and operation plans aiming at a high level of occupant satisfaction should consider personal control opportunities and take into account the moderating effect of control opportunities in multimodal interactions.

Daylight affects human thermal perception

Understanding the factors that affect human thermal responses is necessary to properly design and operate low-energy buildings. It has been suggested that factors not related to the thermal environment can affect thermal responses of occupants, but these factors have not been integrated in thermal comfort models due to a lack of knowledge of indoor factor interactions. While some studies have investigated the effect of electric light on thermal responses, no study exists on the effect of daylight. This study presents the first controlled experimental investigation on the effect of daylight quantity on thermal responses, combining three levels of daylight illuminance (low ~130 lx, medium ~600 lx, and high ~1400 lx) with three temperature levels (19, 23, 27 °C). Subjective and objective thermal responses of 84 participants were collected through subjective ratings on thermal perception and physiological measurements, respectively. Results indicate that the quantity of daylight influences the thermal perception of people specifically resulting in a cross-modal effect, with a low daylight illuminance leading to a less comfortable and less acceptable thermal environment in cold conditions and to a more comfortable one in warm conditions. No effect on their physiological responses was observed. Moreover, it is hypothesised that a warm thermal environment could be tolerated more whenever daylight is present in the room, as compared to the same thermal condition in a room lit with electric lights. Findings further the understanding of factors affecting human thermal responses and thermal adaptation processes in indoor environments and are relevant for both research and practice. The findings suggest that daylight should be considered as a factor in thermal comfort models and in all thermal comfort investigations, as well as that thermal and daylight illuminance conditions should be tuned and changed through the operation and design strategy of the building to guarantee its occupants’ thermal comfort in existing and future structures.

Combined effects of environmental factors on human perception and objective performance: A review of experimental laboratory works

This study reports the outcomes of a literature survey aimed at exploring how different environmental factors-that is acoustic, thermal, visual, and air quality stimuli-interact in affecting building occupants' perception and performance. Recent laboratory studies have been collected, and their methodological approaches reviewed in terms of experimental design, adopted exposures conditions, perception and performance assessment methods. Results have been summarized and compared to identify interaction patterns between environmental factors and possible practical implications for improving the design of both experimental studies and the built environment. The analysis allows highlighting limitations, potential improvements and future opportunities in this field of research, thus providing a reference for further investigations aimed at a deeper understanding, modeling, and prediction of the impacts caused by the main indoor variables on human comfort and performance.

The influence of light on thermal responses

Light is essential for vision and plays an important role in non-visual responses, thus affecting alertness, mood and circadian rhythms. Furthermore, light influences physiological processes, such as thermoregulation, and therefore may be expected to play a role in thermal comfort (TC) as well. A systematic literature search was performed for human studies exploring the relation between ocular light exposure, thermophysiology and TC. Experimental results show that light in the evening can reduce melatonin secretion, delay the natural decline in core body temperature (CBT) and slow down the increase in distal skin temperature. In the morning though, bright light can result in a faster decline in melatonin levels, thus enabling a faster increase in CBT. Moreover, the colour of light can affect temperature perception of the environment. Light with colour tones towards the red end of the visual spectrum leads to a warmer perception compared to more bluish light tones. It should be noted, however, that many results of light on thermal responses are inconclusive, and a theoretical framework is largely lacking. In conclusion, light is capable of evoking thermophysiological responses and visual input can alter perception of the thermal environment. Therefore, lighting conditions should be taken into consideration during thermophysiological research and in the design of indoor climates.

Differential regulation of circadian melatonin rhythm and sleep-wake cycle by bright lights and nonphotic time cues in humans

Our previous study demonstrated that physical exercise under dim lights (<10 lux) accelerated reentrainment of the sleep-wake cycle but not the circadian melatonin rhythm to an 8-h phase-advanced sleep schedule, indicating differential effects of physical exercise on the human circadian system. The present study examined the effects of bright light (>5,000 lux) on exercise-induced acceleration of reentrainment because timed bright lights are known to reset the circadian pacemaker. Fifteen male subjects spent 12 days in temporal isolation. The sleep schedule was advanced from habitual sleep times by 8 h for 4 days, which was followed by a free-run session. In the shift session, bright lights were given during the waking time. Subjects in the exercise group performed 2-h bicycle running twice a day. Subjects in the control kept quiet. As a result, the sleep-wake cycle was fully entrained by the shift schedule in both groups. Bright light may strengthen the resetting potency of the shift schedule. By contrast, the circadian melatonin rhythm was phase-advanced by 6.9 h on average in the exercise group but only by 2.0 h in the control. Thus physical exercise prevented otherwise unavoidable internal desynchronization. Polysomnographical analyses revealed that deterioration of sleep quality by shift schedule was protected by physical exercise under bright lights. These findings indicate differential regulation of sleep-wake cycle and circadian melatonin rhythm by physical exercise in humans. The melatonin rhythm is regulated primarily by bright lights, whereas the sleep-wake cycle is by nonphotic time cues, such as physical exercise and shift schedule.

Circadian Rhythm of Acute Phase Proteins under the Influence of Bright/Dim Light during the Daytime

We investigated the influence of two different light intensities, dim (100 lx) and bright (5000 lx), during the daytime on the circadian rhythms of selected acute phase proteins of C-reactive protein (CRP), alpha1-acid glycoprotein (AGP), alpha1-antichymotrypsin (ACT), transfferin (TF), alpha2-macroglobulin (alpha2-m), haptoglobin (HP), and ceruloplasmin (CP). Serum samples were collected from 7 healthy volunteers at 4 h intervals during two separate single 24 h spans during which they were exposed to the respective light intensity conditions. A circadian rhythm was detected only in ACT concentration in the bright light condition. The concentration of ACT, a positive acute phase protein (APP), increased (significantly significant differences in the ACT concentration were detected at 14:00 and 22:00 h) and AGP showed a tendency to be higher under the daytime bright compared to dim light conditions. There were no significant differences between the time point means under daytime dim and bright light conditions for alpha2-M, AGP, Tf, Cp, or Hp. The findings suggest that some, but not all, APP may be influenced by the environmental light intensity.

Effect of Dim and Bright Light Exposure on Some Immunological Parameters Measured under Thermal Neutral Conditions

This study assesses the effects of ambient light conditions, under a thermoneutral environment, on selected immunological parameters of 7 healthy young women (aged 19 to 22 yrs). Subjects entered the bioclimatic chamber at 11: 00 h, controlled at 26 degrees C and 60% relative humidity, a "neutral climate". They lead a well-regulated life in the climatic chamber (pre-condition) while exposed to dim (200 lux) or, on the next day, bright (5000 lux) light between 06 : 00 to 12 : 00 h. Just before the end of each period of light exposure, a blood sample was taken for later immunological assay of white blood cell count (WBC), phagocytosis, interferon-gamma (IFN-gamma), interleukin-4 (IL-4), CD69 T cells (CD69), CD4+CD25+ T cells (CD4+CD25+), and transforming growth factor-beta 1 (TGF-beta1). The results, when compared with the pre-condition, were as follows: 1) CD69 and IFN-gamma increased during normal conditions without thermal stress under dim light; 2) WBC increased and IL-4 decreased under bright light; 3) as shown by the highly significant decrease of TGF-beta1, the immune system was activated under bright light; 4) phagocytosis tended to increase under bright light exposure; 5) CD69 and IFN-gamma were significantly higher, and CD4+CD25+ tended to decrease under bright light; 6) phagocytosis tended to be lower and TGF-beta1 significantly higher under dim light, indicating a decline of immune system function. Taken together, this preliminary single time-point sampling study infers that some parameters are activated (CD69) while others are attenuated (phagocytosis, TGF-beta1) according to the environmental light intensity, dim vs. bright, in women adhering to a standardized routine in the absence of thermal stress. These findings are discussed in terms of inhibition of the sympathetic and excitation of the parasympathetic nervous system under the influence of life-style regularity and daytime bright light exposure.

How does light intensity influence evening dressing behavior in the cold?

Core temperature (tympanic and rectal temperatures) is lowered for several hours under diurnal bright light exposure and its evening fall is inhibited under evening bright light exposure. Melatonin may be involved in the behavior of these core temperatures. Diurnal bright light exposure for several hours may make dressing behavior and thermal sensibility in the evening cold slower and dull, compared with diurnal dim light exposure. On the contrary, evening bright light exposure for several hours may make the dressing behavior and thermal sensibility in the evening cold quicker and sharper, compared with evening dim light exposure. The underlying physiological mechanisms for these findings are that the thermoregulatory set-point would be reduced more markedly in the evening under the influence of higher elevation of melatonin under the diurnal bright light exposure, and its evening decline would be inhibited by suppression of the nocturnal rise of melatonin under evening bright light exposure.

Effect of evening exposure to dim or bright light on the digestion of carbohydrate in the supper meal

In a previous study we found that daytime exposure to bright as compared to dim light exerted a beneficial effect on the digestion of the evening meal. This finding prompted us to examine whether the digestion of the evening meal is also affected by evening light intensity. Subjects lived in light of 200 lux during the daytime (08:00-17:00 h) and took their evening meal at 17:00 h under 20 lux (evening dim-light condition: 17:00-02:00 h) or 2000 lux (evening bright-light condition: 17:00-02:00 h) until retiring at 02:00 h. Assessment of carbohydrate digestion of the evening meal was accomplished by a breath hydrogen test that is indicative of the malabsorption of dietary carbohydrate. Hydrogen excretion in the breath in the evening under the dim-light condition was significantly less than under the bright-light condition (p < 0.05). This finding is the opposite to that obtained in previous experiments in which subjects were exposed to the different intensities of light during the daytime, and indicates that the exposure to dim light in the evening exerts a better effect on carbohydrate digestion in the evening meal than does the exposure to bright light.

Effects of diurnal bright/dim light intensity on circadian core temperature and activity rhythms in the Japanese macaque

Circadian rhythms of core temperature and activity were studied using three Japanese macaques under influences of two different light intensities during the daytime. Nocturnal core temperature and activity onset time were lower and advanced, respectively, in bright as compared to dim light. These results suggest the possibility that diurnal bright light could influence the circadian organization.

Acute phase proteins, body temperature and urinary melatonin under the influence of bright and dim light intensities during the daytime

Concentrations of five acute phase proteins: C-reactive protein (CRP), alpha 1-antichymotrypsin (ACT), transferin (Tf), alpha 2-macroglobulin (alpha 2-M) and haptoglobin (Hp) as well as glycosylation profiles of alpha 1-antichymotrypsin (ACT) were studied in sera samples with 7 healthy volunteers under the influence of two different light intensities during the daytime dim (100 lx) and bright (3000 lx) light. Concentration of transferin (negative proteins) under the influence of bright light during the daytime decreased significantly. Other proteins have the tendency to increase (positive proteins) under the influence of daytime bright light. The microheterogeneity of ACT did not change under the influence of different light intensities. Melatonin and rectal temperature were also measured simultaneously. Rectal temperature decreased to be lower during the first half of the night and urinary melatonin secretion rate increased to be higher during the night when the subjects spent time under the bright light during the day. Thus, it is concluded that the diurnal bright light exposure may activate some parameters of acute phase proteins, increase nocturnal melatonin secretion and accelerate a fall of rectal temperature during first half period of night sleep.

Influence of light intensities on dressing behavior in elderly people

With civilized environments in modern society, since the people tend to depend more on artificial illumination than on natural illumination which makes less discrepancy between day and night life, clarifying the relationship between human life and illumination is necessary. In our previous studies, we found that the subjects dressed faster with thicker clothing in the morning than in the evening when the room temperature decreased from 30 degrees C to 15 degrees C over 1 hour. We considered these results in terms of load error between the actual and set-point values in the core temperature. The present study was designed to examine the effect of bright light (3,000 lx)/dim light (50 lx) exposure (09:30 h-14:30 h) on dressing behavior and thermoregulatory responses in the elderly people during the afternoon cold exposure. Five female subjects were instructed to dress to feel comfortable when the room temperature was decreased from 30 degrees C to 15 degrees C (15:00 h-17:00 h). The subjects felt cooler and dressed more quickly with thicker clothing after dim light exposure, it is conceivable that the set-point value of core temperature is reduced under the bright light condition. We discussed these results in terms of the establishment of set-point values in the core temperature at bright light condition. If the set-point of the core temperature is lower in the bright than in the dim light condition in present experiment, the dressing behavior with thinner clothing in the bright light condition is advantageous, since it enables the core temperature to reach its set-point value more easily.

Bright light exposure during the daytime affects circadian rhythms of urinary melatonin and salivary immunoglobulin A

The effects of bright light exposure during the daytime on circadian urinary melatonin and salivary immunoglobulin A (IgA) rhythms were investigated in an environmental chamber controlled at a global temperature of 27 degrees C+/-0.2 degrees C and a relative humidity of 60%+/-5%. Seven diurnally active healthy females were studied twice, in bright and dim light conditions. Bright light of 5000 lux was provided by placing fluorescent lamps about 1 meter in front of the subjects during the daytime exposure (06:30-19:30) from 06:30 on day 1 to 10:30 on day 3. Dim light was controlled at 200 lux, and the subjects were allowed to sleep from 22:30 to 06:30 under both light exposure conditions. Urine and saliva were collected at 4h intervals for assessing melatonin and IgA. Melatonin excretion in the urine was significantly greater during the nighttime (i.e., at 06:30 on day 1 and at 02:30 on day 2) after the bright light condition than during the dim light condition. Furthermore, the concentration and the amount of salivary IgA tended to be higher in the bright light than in the dim light condition, especially during the night-time. Also, salivary IgA concentration and the total amount secreted in the saliva were significantly positively correlated with urinary melatonin. These results are consistent with the hypothesis that bright light exposure during the daytime enhances the nocturnal melatonin increase and activates the mucosal immune response.

Visual alliesthesia--cloth color preference in the evening under the influence of different light intensities during the daytime

The primary purpose of this study was to determine the effect of bright and dim light exposure during the daytime on cloth color preference in the evening. Ten healthy female volunteers were exposed to bright light of 5000 lx ("Bright") or dim light of 200 lx ("Dim") from 0730 +/- 1 h to 1800 hours, 200 lx from 1800 hours to 2330 +/- 1 h, and complete darkness during the sleep period (2330 hours +/- 1 h to 0730 +/- 1 h). The subjects were instructed to select the most preferable single one out of 41 cloth colors (24 x 52 cm, 100% cotton), every 5 min from 2100 hours to 2200 hours. Most subjects preferred a warmer cloth color in the Dim condition. The rectal temperature showed clear circadian rhythm both under Bright and Dim conditions but it was significantly lower during sleep in the Bright condition. On the contrary, leg skin temperature was significantly higher during the evening and sleep in the Bright. It is concluded that warmer cloth color is preferred in the evening after Dim condition at an ambient temperature, being based on the higher set point of core temperature after Dim.

Effects of different light intensities during the daytime on circadian rhythm of core temperature in humans

The present study was to determine the effects of bright light exposure during the daytime on core temperature rhythm. Eight female students participated as subjects. They were exposed to bright light of 5000 lux or dim light of 200 lux for 13 hours (06:30-19:30) for two consecutive days. Except the sleep period (22:30-06:30) and during the bright light exposure, light intensity was controlled at 200 lux. Rectal temperature data were collected every 10 min throughout the whole experimental period. The mean level of rectal temperature was not significantly different between the bright and the dim light conditions. However, the evening fall and the morning rise of rectal temperature were significantly greater in the bright light conditions on Day 2 compared to the dim. Furthermore, cosinor analysis showed that the acrophase of rectal temperature rhythm was earlier on Day 2 in the bright light conditions than the dim, and was significantly delayed on Day 2 compared to Day 1 in the dim light conditions. These results suggest that low intensity during the daytime for two consecutive days may induce a phase delay of core temperature rhythm rather than the bright light exposure at least in normally entrained female subjects.

Effects of different types of clothing on circadian rhythms of core temperature and urinary catecholamines

This study investigated the effects of three different types of clothing on the circadian rhythms of core temperature and urinary catecholamines. One type of clothing consisted of long-sleeved shirts, full-length trousers, and socks (Type L, 1,042 g); the second type was of half-sleeved shirts and knee-length trousers (Type H, 747 g); the third type was of Type H during the daytime and Type L during night sleep (Type M). Six healthy females participated in this study where rectal temperature, skin temperatures, heart rate, and urinary catecholamines were continuously measured for 37.5 h at an ambient temperature of 23.8 +/- 0.2 degrees C and a relative humidity of 60 +/- 5%. The results were as follows: (1) The nocturnal minimum of rectal temperature decreased significantly in the sequence Type L < Type M < Type H clothing, and 27.2 and 12.4% of the circadian amplitude were influenced by type of clothing during the daytime and the nighttime, respectively. (2) The rise of skin temperatures in the extremities increased significantly more after the subjects retired for sleep with Type M or Type H clothing than with Type L. (3) Urinary catecholamines decreased more in the evening and increased more in the morning with Type H and Type M clothing than with Type L. These results show that the circadian rhythm of core temperature, especially the nocturnal minimum value, was influenced by the type of clothing worn not only during the nighttime, but also during the daytime.

Influence of two different light intensities during daytime on endurance performance of handgrip exercise

The effect of two different light intensities (dim, 50 lux and bright, 5,000 lux) on handgrip exercise in a climatic chamber (26 degrees C, 60% relative humidity) were studied in eight female subjects, aged 20-24 years. The subjects were in either the dim or bright light from 1000 hours to 1800 hours. They were then in 50 lux from 1800 hours to 2200 hours in complete darkness from 2200 hours to 0600 hours (sleep), and again in 50 lux from 0600 hours to 0800 hours. They were instructed to perform handgrip exercise with a hand ergometer until the occurrence of exhaustion from 0600 hours. The influence of dim and bright intensities during the previous daytime on the number of contractions was compared. The main findings were firstly that the mean number of contractions was 766.63 SEM 43.28 in dim and 864.5 SEM 54.76 in bright intensities (P < 0.01), and secondly that rectal temperatures were slightly but significantly lower in the bright than in the dim intensities. The reason for the reduced number of contractions in dim was discussed in terms of the establishment of a higher set-point in the core temperature in dim.