Bell 2016.

Study characteristics
Methods	Parallel RCT, individuals randomised
Data	UK, primary care setting. All host trial participants, as a source of the retention trial sample. Host trial participants from 5 centres were followed up using postal questionnaires at the fifth year of follow‐up. Total n = 7,655; range age 70‐85 years; 100% females.
Comparisons	Intervention group received trial‐branded pen with the 60‐month follow‐up questionnaire. Control group 60‐month follow‐up questionnaire alone.
Outcomes	Questionnaire return.
Notes	Retention period: 60 months follow‐up.
Risk of bias
Item	Authors' judgement	Support for judgement
Allocation concealment?	Unclear	Not reported in the paper.
Adequate sequence generation?	Yes	A computer‐randomisation package was used to allocate all eligible participants
Blinding of participants and personnel?	Yes	Not reported in the paper but unblinding not likely to impact objective outcome
Blinding of outcome assessment?	Yes	Not reported in the paper. However, objective outcome, staff have no plausible additional opportunity to influence postal response rate once questionnaires sent.
Incomplete outcome data addressed? All outcomes	Yes	No concerns raised.
Free of selective outcome reporting?	Yes	No concerns raised.
Other sources of bias	Yes	No further concerns raised.
Overall Risk of Bias	Unclear	Unclear