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Predicting missing biomarker data in a longitudinal study of Alzheimer disease.

Abstract

OBJECTIVE
To investigate predictors of missing data in a longitudinal study of Alzheimer disease (AD).
METHODS
The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a clinic-based, multicenter, longitudinal study with blood, CSF, PET, and MRI scans repeatedly measured in 229 participants with normal cognition (NC), 397 with mild cognitive impairment (MCI), and 193 with mild AD during 2005-2007. We used univariate and multivariable logistic regression models to examine the associations between baseline demographic/clinical features and loss of biomarker follow-ups in ADNI.
RESULTS
CSF studies tended to recruit and retain patients with MCI with more AD-like features, including lower levels of baseline CSF Aβ(42). Depression was the major predictor for MCI dropouts, while family history of AD kept more patients with AD enrolled in PET and MRI studies. Poor cognitive performance was associated with loss of follow-up in most biomarker studies, even among NC participants. The presence of vascular risk factors seemed more critical than cognitive function for predicting dropouts in AD.
CONCLUSION
The missing data are not missing completely at random in ADNI and likely conditional on certain features in addition to cognitive function. Missing data predictors vary across biomarkers and even MCI and AD groups do not share the same missing data pattern. Understanding the missing data structure may help in the design of future longitudinal studies and clinical trials in AD.

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    • Authors

    Lo RY, Jagust WJ, Alzheimer's Disease Neuroimaging Initiative

    Institution

    Division of Epidemiology, University of California, Berkeley, USA. rlo@berkeley.edu

    Source

    Neurology 78:18 2012 May 1 pg 1376-82

    MeSH

    Alzheimer Disease
    Amyloid beta-Peptides
    Biological Markers
    Cohort Studies
    Dementia, Vascular
    Fluorodeoxyglucose F18
    Homocysteine
    Humans
    Logistic Models
    Longitudinal Studies
    Magnetic Resonance Imaging
    Mild Cognitive Impairment
    Neuropsychological Tests
    Patient Dropouts
    Peptide Fragments
    Positron-Emission Tomography
    Research Design
    Risk Factors
    tau Proteins

    Pub Type(s)

    Journal Article
    Research Support, N.I.H., Extramural
    Research Support, Non-U.S. Gov't

    Language

    eng

    PubMed ID

    22491869