Characteristics of non-responders to self-reported questionnaires in a large inflammatory bowel disease cohort study.
BACKGROUND
A major threat to the validity of longitudinal cohort studies is non-response to follow-up, which can lead to erroneous conclusions. The objective of this study was to evaluate the profile of non-responders to self-reported questionnaires in the Swiss inflammatory bowel disease (IBD) Cohort.


METHODS
We used data from adult patients enrolled between November 2006 and June 2011. Responders versus non-responders were compared according to socio-demographic, clinical and psychosocial characteristics. Odds ratio for non-response to initial patient questionnaire (IPQ) compared to 1-year follow-up questionnaire (FPQ) were calculated.


RESULTS
A total of 1943 patients received IPQ, in which 331 (17%) did not respond. Factors inversely associated with non-response to IPQ were age >50 and female gender (OR = 0.37; p < 0.001 respectively OR = 0.63; p = 0.003) among Crohn's disease (CD) patients, and disease duration >16 years (OR = 0.48; p = 0.025) among patients with ulcerative colitis (UC). FPQ was sent to 1586 patients who had completed the IPQ; 263 (17%) did not respond. Risk factors of non-response to FPQ were mild depression (OR = 2.17; p = 0.003) for CD, and mild anxiety (OR = 1.83; p = 0.024) for UC. Factors inversely associated with non-response to FPQ were: age >30 years, colonic only disease location, higher education and higher IBD-related quality of life for CD, and age >50 years or having a positive social support for UC.


CONCLUSIONS
Characteristics of non-responders differed between UC and CD. The risk of non-response to repetitive solicitations (longitudinal versus transversal study) seemed to decrease with age. Assessing non-respondents' characteristics is important to document potential bias in longitudinal studies.
University of Lausanne , Lausanne , Switzerland.
Eléonore
E
Multone
John-Paul
JP
Vader
Christian
C
Mottet
Alain
A
Schoepfer
Nicolas
N
Fournier
Bernard
B
Burnand
Pierre
P
Michetti
Valérie
V
Pittet
D000328:Adult; D000367:Age Factors; D001007:Anxiety; D003093:Colitis, Ulcerative / Q000523:psychology*; D003424:Crohn Disease / Q000523:psychology*; D003863:Depression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D059012:Lost to Follow-Up; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011788:Quality of Life; D012307:Risk Factors; D015983:Selection Bias; D057566:Self Report; D011795:Surveys and Questionnaires; D013557:Switzerland
Crohn’s disease; cohort study; inflammatory bowel disease; selection bias; self-administrated questionnaires; ulcerative colitis