Abstract
Background: Missing data are common in longitudinal studies, and more so, in studies of older adults, who are
susceptible to health and functional decline that limit completion of assessments. We assessed the extent, current
reporting, and handling of missing data in longitudinal studies of older adults.
Methods: Medline and Embase databases were searched from 2015 to 2019 for publications on longitudinal observational
studies conducted among persons ≥55 years old. The search was restricted to 10 general geriatric journals
published in English. Reporting and handling of missing data were assessed using questions developed from the
recommended standards. Data were summarised descriptively as frequencies and proportions.
Results: A total of 165 studies were included in the review from 7032 identified records. In approximately half of the
studies 97 (62.5%), there was either no comment on missing data or unclear descriptions. The percentage of missing
data varied from 0.1 to 55%, with a 14% average among the studies that reported having missing data. Complete case
analysis was the most common method for handling missing data with nearly 75% of the studies (n = 52) excluding
individual observations due to missing data, at the initial phase of study inclusion or at the analysis stage. Of the 10
studies where multiple imputation was used, only 1 (10.0%) study followed the guideline for reporting the procedure
fully using online supplementary documents.
Conclusion: The current reporting and handling of missing data in longitudinal observational studies of older adults
are inadequate. Journal endorsement and implementation of guidelines may potentially improve the quality of missing
data reporting. Further, authors should be encouraged to use online supplementary files to provide additional
details on how missing data were addressed, to allow for more transparency and comprehensive appraisal of studies.