When is baseline adjustment useful in analyses of change? An example with education and cognitive change.

TitleWhen is baseline adjustment useful in analyses of change? An example with education and cognitive change.
Publication TypeJournal Article
Year of Publication2005
AuthorsM. Glymour, M, Weuve, J, Berkman, LF, Kawachi, I, Robins, JM
JournalAm J Epidemiol
Date Published2005 Aug 01
ISSN Number0002-9262
Call Numberpubs_2005_Glymour_etal.pdf
KeywordsAge Factors, Aged, Bias, Cognition Disorders, Educational Status, Epidemiologic Methods, Female, Health Status, Humans, Longitudinal Studies, Male, Models, Statistical, Neuropsychological tests, Regression Analysis, United States

In research on the determinants of change in health status, a crucial analytic decision is whether to adjust for baseline health status. In this paper, the authors examine the consequences of baseline adjustment, using for illustration the question of the effect of educational attainment on change in cognitive function in old age. With data from the US-based Assets and Health Dynamics Among the Oldest Old survey (n = 5,726; born before 1924), they show that adjustment for baseline cognitive test score substantially inflates regression coefficient estimates for the effect of schooling on change in cognitive test scores compared with models without baseline adjustment. To explain this finding, they consider various plausible assumptions about relations among variables. Each set of assumptions is represented by a causal diagram. The authors apply simple rules for assessing causal diagrams to demonstrate that, in many plausible situations, baseline adjustment induces a spurious statistical association between education and change in cognitive score. More generally, when exposures are associated with baseline health status, this bias can arise if change in health status preceded baseline assessment or if the dependent variable measurement is unreliable or unstable. In some cases, change-score analyses without baseline adjustment provide unbiased causal effect estimates when baseline-adjusted estimates are biased.

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Endnote Keywords

Methodology/EDUCATION/Health-cognitive ability

Endnote ID


Alternate JournalAm J Epidemiol
Citation Key7055
PubMed ID15987729
Grant ListR37 AI032475 / AI / NIAID NIH HHS / United States
AG000158 / AG / NIA NIH HHS / United States
AG023399 / AG / NIA NIH HHS / United States