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Cohort effect

The inhabitants of Vlaardingen and Vlagtwedde participated in a longitudinal study, which included measurements of FEV1 and FVC. After 12 years up to 5 measurements were available for each subject. This allows investigating to what extent cross-sectional and longitudinal findings disclose the same age-related trends in spirometry. The results are depicted in the animation below.

The main findings are:

It follows that in repeated measurements on the same person one should be careful in making comparisons with the observed longitudinal behavior and the age-related trend derived from cross-sectional studies. The latter, for one thing, comprises:

  1. a cohort effect
  2. an intra-individual effect of aging.
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