Adamsson Mathias, Laike Thorbjörn, Morita Takeshi
School of Engineering, Jönköping University, P.O. Box 1026, SE-551 11, Jönköping, Sweden.
Department of Architecture and Built Environment, Lund University, P.O. Box 118, SE-221 00, Lund, Sweden.
J Physiol Anthropol. 2016 Jul 19;36(1):6. doi: 10.1186/s40101-016-0103-9.
Seasonal variations in physiology and behavior have frequently been reported. Light is the major zeitgeber for synchronizing internal circadian rhythms with the external solar day. Non-image forming effects of light radiation, for example, phase resetting of the circadian rhythms, melatonin suppression, and acute alerting effects, depend on several characteristics of the light exposure including intensity, timing and duration, spectral composition and previous light exposure, or light history. The aim of the present study was to report on the natural pattern of diurnal and seasonal light exposure and to examine seasonal variations in the circadian change of melatonin and cortisol concentrations for a group of Swedish office workers.
Fifteen subjects participated in a field study that was carried out in the south of Sweden. Ambulatory equipment was used for monthly measurements of the daily exposure to light radiation across the year. The measurements included illuminance and irradiance. The subjects collected saliva samples every 4 h during 1 day of the monthly measuring period.
The results showed that there were large seasonal differences in daily amount of light exposure across the year. Seasonal differences were observed during the time periods 04:00-08:00, 08:00-12:00, 12:00-16:00, 16:00-20:00, and 20:00-24:00. Moreover, there were seasonal differences regarding the exposure pattern. The subjects were to a larger extent exposed to light in the afternoon/evening in the summer. During the winter, spring, and autumn, the subjects received much of the daily light exposure in the morning and early afternoon. Regarding melatonin, a seasonal variation was observed with a larger peak level during the winter and higher levels in the morning at 07:00.
This study adds to the results from other naturalistic studies by reporting on the diurnal and seasonal light exposure patterns for a group living at a northern latitude of 56° N, with large annual variations in photoperiod length. It seems to be seasonal variation in the lighting conditions, both concerning intensities as well as regarding the pattern of the light exposure to which people living at high latitudes are exposed which may result in seasonal variation in the circadian profile of melatonin.
生理学和行为的季节性变化屡有报道。光是使内部昼夜节律与外部太阳日同步的主要授时因子。光辐射的非成像效应，例如昼夜节律的相位重置、褪黑素抑制和急性警觉效应，取决于光照的几个特征，包括强度、时间和持续时间、光谱组成以及先前的光照暴露或光照历史。本研究的目的是报告瑞典上班族群体的昼夜和季节性光照暴露自然模式，并研究褪黑素和皮质醇浓度昼夜变化的季节性差异。
15名受试者参与了在瑞典南部进行的一项现场研究。使用动态监测设备全年每月测量每日光照暴露情况。测量包括照度和辐照度。在每月测量期的1天内，受试者每4小时采集一次唾液样本。
结果表明，全年每日光照暴露量存在很大的季节性差异。在04:00 - 08:00、08:00 - 12:00、12:00 - 16:00、16:00 - 20:00和20:00 - 24:00时间段观察到季节性差异。此外，光照模式也存在季节性差异。夏季时，受试者在下午/晚上受到更多光照。在冬季、春季和秋季，受试者在上午和下午早些时候接受了大部分日常光照。关于褪黑素，观察到季节性变化，冬季峰值水平更大，且在07:00时上午水平更高。
本研究通过报告居住在北纬56°的群体的昼夜和季节性光照暴露模式，补充了其他自然主义研究的结果，该地区光周期长度存在较大的年度变化。高纬度地区居民所接触的光照条件似乎存在季节性变化，这可能导致褪黑素昼夜节律的季节性变化。
