Department of Psychology, Institute for Mind and Biology, University of Chicago, Chicago, IL 60637, USA.
J Biol Rhythms. 2011 Aug;26(4):345-52. doi: 10.1177/0748730411409708.
Amplitude of the seasonal change in day length increases with distance from the equator, and changes in day length markedly alter immune function in diverse nonhuman animal models of infection. Historical records of mortality data, ambient temperature, population density, geography, and economic indicators from 42 countries during 1918-1920 were analyzed to determine relative contributions toward human mortality during the "Spanish" influenza pandemic of 1918-1920. The data identify a strong negative relation between distance from the equator and mortality during the 1918-1920 influenza pandemic, which, in a multiple regression model, manifested independent of major economic, demographic, and temperature variables. Enhanced survival was evident in populations that experienced a winter nadir day length ≤10 h light/day, relative to those that experienced lower amplitude changes in photoperiod. Numerous reports indicate that exposure to short day lengths, typical of those occurring outside the tropics during winter, yields robust and enduring reductions in the magnitude of cytokine, febrile, and behavioral responses to infection. The present results are preliminary but prompt the conjecture that, if similar mechanisms are operant in humans, then they would be predicted to mitigate symptoms of infection in proportion to an individual's distance from the equator. Although limitations and uncertainties accompany regression-based analyses of historical epidemiological data, latitude, per se, may be an underrecognized factor in mortality during the 1918-1920 influenza pandemic. The author proposes that some proportion of the global variance in morbidity and mortality from infectious diseases may be explained by effects of day length on the innate immune response to infection.
昼夜长度季节性变化的幅度随与赤道的距离增加而增加，并且昼夜长度的变化显著改变了多种非人类动物感染模型中的免疫功能。分析了 1918-1920 年 42 个国家的死亡率数据、环境温度、人口密度、地理位置和经济指标的历史记录，以确定在 1918-1920 年“西班牙”流感大流行期间对人类死亡率的相对贡献。数据表明，与赤道的距离与 1918-1920 年流感大流行期间的死亡率之间存在很强的负相关关系，在多元回归模型中，这种关系独立于主要的经济、人口和温度变量。在经历冬季最低日长≤10 小时光照/天的人群中，生存能力增强，与经历光周期振幅变化较小的人群相比，生存能力增强。许多报告表明，暴露于短日长，类似于冬季在热带以外发生的日长，会导致细胞因子、发热和行为对感染的反应幅度显著降低，且具有持久性。目前的结果是初步的，但促使人们猜测，如果类似的机制在人类中起作用，那么它们将根据个体与赤道的距离成比例地减轻感染症状。尽管对历史流行病学数据进行回归分析存在局限性和不确定性，但纬度本身可能是 1918-1920 年流感大流行期间死亡率的一个未被充分认识的因素。作者提出，某些传染病发病率和死亡率的全球差异可能部分归因于昼夜长度对感染的固有免疫反应的影响。
