Attrition in an exercise intervention: a comparison of early and later dropouts.
OBJECTIVE
To identify reasons for dropout and factors that may predict dropout from an exercise intervention aimed at improving physical function in frail older persons.


METHODS
An 18-month randomized controlled intervention in a community setting. The intervention comprised 2 groups: class-based and self-paced exercise.


METHODS
155 community-dwelling older persons, mean age 77.4, with mildly to moderately compromised mobility.


METHODS
The primary outcome measure was dropout. Dropouts were grouped as: D0, dropout between baseline and 3-month assessment, and D3, dropout after 3-month assessment.


METHODS
Measurements of demographics, health, and physical performance included self-rated health, SF-36, disease burden, adverse events, PPT-8, MacArthur battery, 6-minute walk, and gait velocity.


RESULTS
There were 56 dropouts (36%), 31 in first 3 months. Compared with retained subjects (R), the D0 group had greater disease burden (P = .011), worse self-perceived physical health (P = .014), slower usual gait speed (P = .001), and walked a shorter distance over 6 minutes (P<.001). No differences were found between R and D3. Multinomial logistic regression showed 6-minute walk (P<.001) and usual gait velocity (P<.001) were the strongest independent predictors of dropout. Controlling for all other variables, adverse events after randomization and 6-minute walk distance were the strongest independent predictors of dropout, and self-paced exercise assignment increased the risk of dropout.


CONCLUSIONS
We observed baseline differences between early dropouts and retained subjects in disease burden, physical function, and endurance, suggesting that these factors at baseline may predict dropout. Improved understanding of factors that lead to and predict dropout could allow researchers to identify subjects at risk of dropout before randomization. Assigning targeted retention techniques in accordance with these factors could result in decreased attrition in future studies. Therefore, the results of selective attrition of frailer subjects, such as decreased heterogeneity, restricted generalizability of study findings, and limited understanding of exercise effects in this population, would be avoided.
Schmidt
J A
JA
Dept of Neurology, UConn Health Center, Farmington, Connecticut 06030-1840, USA.
Gruman
C
C
King
M B
MB
Wolfson
L I
LI
D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D005080:Exercise Test; D005081:Exercise Therapy / Q000009:adverse effects; D005260:Female; D016330:Frail Elderly / Q000523:psychology* / Q000706:statistics & numerical data; D015577:Geriatric Assessment; D006304:Health Status; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D010352:Patient Dropouts / Q000523:psychology* / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011795:Surveys and Questionnaires; D013997:Time Factors; D016138:Walking