Hébert M, Dumont M, Paquet J
Laboratoire de chronobiologie, Hôpital du Sacré-Coeur de Montréal, Université de Montréal, Québec, Canada.
Chronobiol Int. 1998 Jan;15(1):59-70. doi: 10.3109/07420529808998670.
Little is known about the natural pattern of seasonal and diurnal illumination to which normal people are exposed, especially in northern latitudes. In this study, ambient illumination of normal volunteers living at a latitude of 45 degrees 31' N was recorded with ambulatory photosensors worn for 5 to 6 days in winter and summer. Results from 12 normal subjects (6 men, 6 women) aged 18 to 35 years were included in the analyses. The mean daily duration of time awake was similar in both seasons: 14.6h in the summer and 14.9h in the winter. However, the phase of the sleep-wake cycle was advanced in the summer compared to the winter, as shown by an earlier average waketime and bedtime in the summer. Illumination recorded by the ambulatory monitor between waketime and bedtime was categorized according to four ranges of light intensities: very dim (< 1 lux), dim (1-100 lux), moderate (100-1000 lux), and bright (> 1000 lux) illumination. There was no seasonal difference for the time spent in illumination lower than 1000 lux, but the duration of daily exposure to bright light averaged 2.6h in the summer compared to only 0.4h in the winter (p = 0.0004). To evaluate the diurnal distribution of ambient illumination, time spent awake was divided into four time intervals: morning (waketime to 12:00), afternoon (12:00 to 16:00), early evening (16:00 to 20:00), and late evening (20:00 to bedtime). Except for late evening, the time spent in bright illumination was significantly longer during the summer for all time intervals, but the relative distribution of bright light exposure throughout the day was the same in both seasons. The subjects spent more than 50% of their time awake in illumination dimmer than 100 lux, even in the summer. More naturalistic studies are needed to determine whether very short exposure to bright light or longer exposure to light of moderate intensity (100-1000 lux) are sufficient to maintain circadian entrainment and euthymia in normal young subjects.
对于正常人所接触的季节性和昼夜光照的自然模式，我们知之甚少，尤其是在北纬地区。在本研究中，居住在北纬45度31分的正常志愿者的环境光照，通过在冬季和夏季佩戴5至6天的便携式光传感器进行记录。分析纳入了12名年龄在18至35岁的正常受试者（6名男性，6名女性）的结果。两个季节中平均每日清醒时间相似：夏季为14.6小时，冬季为14.9小时。然而，与冬季相比，夏季的睡眠 - 觉醒周期阶段提前，表现为夏季的平均起床时间和就寝时间更早。便携式监测器记录的清醒时间和就寝时间之间的光照，根据四个光照强度范围进行分类：非常昏暗（<1勒克斯）、昏暗（1 - 100勒克斯）、中等（100 - 1000勒克斯）和明亮（>1000勒克斯）光照。低于1000勒克斯的光照时间没有季节性差异，但夏季每日暴露于明亮光照的持续时间平均为2.6小时，而冬季仅为0.4小时（p = 0.0004）。为了评估环境光照的昼夜分布，将清醒时间分为四个时间间隔：早晨（起床时间至12:00）、下午（12:00至16:00）、傍晚（16:00至20:00）和深夜（20:00至就寝时间）。除深夜外，夏季所有时间间隔内处于明亮光照下的时间明显更长，但两个季节中全天明亮光照暴露的相对分布相同。即使在夏季，受试者清醒时间的50%以上是在低于100勒克斯的光照下度过的。需要更多自然主义的研究来确定，对于正常年轻受试者，极短时间暴露于明亮光照或较长时间暴露于中等强度光照（100 - 1000勒克斯）是否足以维持昼夜节律同步和心境正常。
