Ahacic Kozma, Parker Marti G, Thorslund Mats
Aging Research Center, Karolinska Institute and Stockholm University, Box 6401, 113 82 Stockholm, Sweden.
Department of social work, Stockholm University, Stockholm, Sweden.
Eur J Ageing. 2007 May 10;4(2):83-91. doi: 10.1007/s10433-007-0049-1. eCollection 2007 Jun.
By corroborating cross-sectional with longitudinal analyses, this study illustrates how cohort effects can confound trends over age and time. Mobility (walking difficulties) and edentulousness (toothlessness) were studied from 1968 to 2002 in a nationally representative panel aged 18-75 (5 waves, ≈ 5,000) and ages 77+ at later waves (2 waves, ≈ 500). Three analyses were done: cross-sectional 10-year age group differences in 5 waves, time-lag differences between waves (shifts across time) for age groups, and within-cohort differences between waves for 10-year birth cohorts followed over time. Complementary age-period-cohort models using logistic regression analysis evaluated differences. Both mobility and edentulousness have earlier been shown to be strongly related to age cross-sectionally. For mobility, cross-sectional and longitudinal analyses showed large changes, whereas time-lag analysis indicated no or marginal changes. Both cross-sectional and longitudinal results showed an exponential curvilinear age dependency for mobility limitations, with limitations becoming more usual in older ages. In contrast, cross-sectional and time-lag analyses of edentulousness showed large differences, whereas longitudinal analysis indicated no or marginal changes. Rates of edentulousness became increasingly lower for successively later cohorts in a curvilinear fashion. These patterns demonstrate that age effects dominated mobility, whereas cohort effects dominated edentulousness. Age-period-cohort models confirmed these findings. The cohort effect of edentulousness implies that the cohorts' movement through time gives a false impression of age and period effects in cross-sectional data.
通过将横断面分析与纵向分析相结合，本研究阐明了队列效应如何混淆年龄和时间趋势。1968年至2002年期间，对一个具有全国代表性的年龄在18 - 75岁的样本组（共5轮，约5000人）以及后期几轮中77岁及以上的人群（2轮，约500人）的行动能力（行走困难）和无牙情况进行了研究。进行了三项分析：5轮中10岁年龄组的横断面差异、各年龄组不同轮次之间的时间滞后差异（随时间推移的变化）以及随时间跟踪的10年出生队列在不同轮次之间的队列内差异。使用逻辑回归分析的互补年龄 - 时期 - 队列模型评估了差异。此前已表明，行动能力和无牙情况在横断面研究中都与年龄密切相关。对于行动能力，横断面分析和纵向分析显示出较大变化，而时间滞后分析表明变化不大或几乎没有变化。横断面和纵向结果均显示行动能力受限呈指数曲线年龄依赖性，在老年时受限情况更为常见。相比之下，无牙情况的横断面分析和时间滞后分析显示出较大差异，而纵向分析表明变化不大或几乎没有变化。无牙率在各相继队列中呈曲线下降趋势，且越来越低。这些模式表明年龄效应主导了行动能力，而队列效应主导了无牙情况。年龄 - 时期 - 队列模型证实了这些发现。无牙情况的队列效应意味着各队列随时间推移的变化在横断面数据中给人一种年龄和时期效应的错误印象。
