Abstract
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, n ≈ 5,000) and ages 77+ at later waves (2 waves, n ≈ 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.
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Acknowledgments
This research was performed with financial support from the Swedish Council for Working Life and Social Research (grants 2003-0539 and 2003-0515) and the Swedish Research Council (grant 2005-2182).
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Ahacic, K., Parker, M.G. & Thorslund, M. Aging in disguise: age, period and cohort effects in mobility and edentulousness over three decades. Eur J Ageing 4, 83–91 (2007). https://doi.org/10.1007/s10433-007-0049-1
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DOI: https://doi.org/10.1007/s10433-007-0049-1