Holford T R, Zheng T, Mayne S T, McKay L A
Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06510.
Cancer Res. 1992 Oct 1;52(19 Suppl):5443s-5446s.
Factors that need to be considered in the analysis of time trends in disease incidence are age, year of diagnosis, and birth cohort. When these are included in a log-linear model, a nonidentifiability problem arises from the linear dependence among these three time factors so that only specified functions of the parameters can be unambiguously determined. One of these invariant functions is the drift or the sum of the period and cohort trend. Non-Hodgkin's lymphoma incidence rates from Connecticut for the period 1935-1989 were analyzed for males and females. In addition to an age effect, both period and cohort significantly improved the fit of the model. The estimated drift shows that there has been a 10.3% increase in risk every 5 years since 1965 for females and 9.2% for males. It is unlikely that a trend of this magnitude can be attributed entirely to data artifact.
在分析疾病发病率的时间趋势时需要考虑的因素有年龄、诊断年份和出生队列。当将这些因素纳入对数线性模型时，由于这三个时间因素之间的线性相关性会出现不可识别问题，因此只能明确确定参数的特定函数。这些不变函数之一是漂移或时期和队列趋势的总和。对1935年至1989年期间康涅狄格州男性和女性的非霍奇金淋巴瘤发病率进行了分析。除年龄效应外，时期和队列均显著改善了模型的拟合度。估计的漂移表明，自1965年以来，女性每5年风险增加10.3%，男性增加9.2%。如此大的趋势不太可能完全归因于数据假象。
