How did regional lockdowns during the COVID-19 pandemic affect recruitment into a large multinational cohort study of intrauterine device users?

OBJECTIVES

To investigate the impact of lockdown policies on the recruitment of an ongoing cohort study.

STUDY

DESIGN

We performed descriptive analyses of recruitment, dropout, and baseline characteristics over time. Oxford Stringency Index was used to assess the impact of regional constraints on recruitment.

RESULTS

Drop in recruitment clearly reflected the Stringency Index within the first months of the pandemic. Unexpectedly, drop-out rates declined in 2020/2021. Baseline characteristics were comparable, yet younger women were recruited more frequently during the pandemic.

CONCLUSIONS

There was no strong evidence of recruitment bias due to the pandemic.

IMPLICATIONS: The COVID-19 pandemic is a potential source of bias for ongoing studies and its influence on the study conduct (e.g., recruitment, drop-out) should be thoroughly evaluated to ensure that study results are not biased in this regard. The Oxford's Government Stringency Index can be used to identify pandemic-affected time periods.