Natural light exposure, sleep and depression among day workers and shiftworkers at Arctic and Equatorial latitudes

Objectives: This study aimed to investigate the relationship between individual natural light exposure, sleep need, and depression at two latitudes, one extreme with a few hours of light per day during winter, and the other with equal hours of light and darkness throughout the year. Methods: This cross-sectional study included a sample of Brazilian workers (Equatorial, n = 488 workers) and a Swedish sample (Arctic, n = 1,273). Results: The reported mean total natural light exposure per 4-week cycle differed significantly between the Equatorial and Arctic regions. However, shiftworkers from both sites reported similar hours of natural light exposure. Short light exposure was a predictor for insufficient sleep. Conclusion: Reduced exposure to natural light appears to increase the perception of obtaining insufficient sleep. Arctic workers were more prone to develop depression than Equatorial workers.

研究目的：本研究旨在探究两种纬度环境下，个体自然光暴露量、睡眠需求与抑郁状态之间的关联；其中一种为冬季每日光照时长极短的极端高纬度环境，另一种为全年昼夜时长均等的环境。
研究方法：本项横断面研究纳入了巴西工人队列（赤道区域，n=488）与瑞典工人队列（北极区域，n=1273）。
研究结果：赤道与北极区域的受试者报告的每4周周期内平均总自然光暴露量存在显著差异。然而，两地的轮班工人报告的自然光暴露时长较为相近。短时长自然光暴露是睡眠不足的预测因素。
研究结论：自然光暴露量减少似乎会加重睡眠不足的主观感知。北极区域工人相较于赤道区域工人更易出现抑郁症状。