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Diabetes Obes Metab. 2019 Sep;21(9):2029-2038. doi: 10.1111/dom.13766. Epub 2019 May 29.

Glucose-lowering medications and the risk of cancer: A methodological review of studies based on real-world data.

Author information

1
Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
2
Science, Aetion Inc., Boston, Massachusetts.
3
Optum Epidemiology, Boston, Massachusetts.

Abstract

AIM:

To review the methodology of observational studies examining the association between glucose-lowering medications and cancer to identify the most common methodological challenges and sources of bias.

METHODS:

We searched PubMed systematically to identify observational studies on glucose-lowering medications and cancer published between January 2000 and January 2016. We assessed the design and analytical methods used in each study, with a focus on their ability to achieve study validity, and further evaluated the prevalence of major methodological choices over time.

RESULTS:

Of 155 studies evaluated, only 26% implemented a new-user design, 41% used an active comparator, 33% implemented a lag or latency period, and 51% adjusted for diabetes duration. Potential for immortal person-time bias was identified in 63% of the studies; 55% of the studies adjusted for variables measured during the follow-up without appropriate statistical methods. Aside from a decreasing trend in adjusting for variables measured during the follow-up, we observed no trends in methodological choices over time.

CONCLUSIONS:

The prevalence of well-known design and analysis flaws that may lead to biased results remains high among observational studies on glucose-lowering medications and cancer, limiting the conclusions that can be drawn from these studies. Avoiding known pitfalls could substantially improve the quality and validity of real-world evidence in this field.

KEYWORDS:

bias; cancer; epidemiological methods; glucose-lowering medications; review

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