Russell D, Douglas A S, Allan T M
Department of Public Health, Medical School, University of Aberdeen, Foresterhill.
J Epidemiol Community Health. 1993 Oct;47(5):362-7. doi: 10.1136/jech.47.5.362.
Seasonality of birth was examined to determine whether this has changed over the last half century.
Time-series analysis was carried out on retrospective data, both for the full 50 year period and for the five decades within that period. Although the primary objective was to investigate seasonality by fitting an appropriate model and examining changes over the period studied, non-seasonal trends were also examined.
Data by month were obtained from the Registrar General on all births in Scotland during the years 1938-87.
There was a total of 4,325,000 births in the 50 years examined.
There are two peaks to the seasonality rhythm--one wide, in spring/early summer and one narrow, in October. Cosinor analysis, modified to allow for the second peak, was used to fit a sine curve model. Analysis of variance showed that this was adequate and established the significance of both peaks. The main peak of seasonal excess rose to a maximum in 1948-57, and thereafter declined by two thirds. While the position of the main peak moved forward two months over the 50 years, the October peak remained unchanged until the final decade, when it rose slightly; thus its relative importance increased steadily from 1948 onwards.
The changing biological rhythm may be related to alterations in the climate and environment or to social differences.
研究出生季节性，以确定在过去半个世纪中其是否发生了变化。
对回顾性数据进行时间序列分析，数据涵盖整个50年期间以及该期间内的五个十年。虽然主要目的是通过拟合适当模型并研究研究期间的变化来调查季节性，但也研究了非季节性趋势。
每月数据来自苏格兰总登记官，涵盖1938年至1987年期间苏格兰的所有出生情况。
在研究的50年中共有432.5万例出生。
季节性节律有两个峰值——一个较宽，出现在春季/初夏；另一个较窄，出现在10月。采用经修改以考虑第二个峰值的余弦分析来拟合正弦曲线模型。方差分析表明该模型是合适的，并确定了两个峰值的显著性。季节性超额的主要峰值在1948年至1957年达到最大值，此后下降了三分之二。在这50年中，主要峰值的位置提前了两个月，而10月的峰值直到最后十年才保持不变，随后略有上升；因此，从1948年起其相对重要性稳步增加。
生物节律的变化可能与气候和环境的改变或社会差异有关。
