We appreciate Zhang's comment (1) on our recent article (2). Our study concluded that type 2 diabetes mellitus (DM) “was inversely associated with adenoma risk in women older than 55 years … but not in women 55 years or younger” (2).
This finding was unexpected, and we hypothesized that it could be related to changes in diet and other lifestyle factors after a DM diagnosis or to the use of metformin for the treatment of DM. We mentioned the small sample size for stratified analyses and the lack of details on metformin use as possible limitations of our study (2). Zhang suggests that differential use of screening endoscopy by DM status could also be a possible source of bias in our study, with DM patients being more likely to receive colorectal cancer (CRC) screening compared to women without DM (1). We believe this is unlikely because only those participants who reported undergoing a screening colonoscopy or sigmoidoscopy for CRC were eligible to be included in our nested case-control analysis (2).
Moreover, evidence of the association of DM with a higher likelihood of receiving CRC screening is conflicting. A study using National Health Interview Survey data did not find an association between DM and CRC screening among women (3). Another study using Medicare claims data suggested that CRC screening rates are lower among elderly diabetic women compared to those without diabetes (4).
Acknowledgments
Conflict of interest: none declared.
References
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