August 01, 2019
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Metformin use reduces risk for varicose veins

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Use of metformin appeared to reduce the risk for varicose veins among adults with type 2 diabetes, according to findings from a retrospective cohort study published in Diabetes Metabolism Research and Reviews.

“The study supported the use of metformin as a first-line treatment for type 2 diabetes mellitus in view of its extra bonus beyond glycemic control,” Chin-Hsiao Tseng, MD, PhD, a professor in the department of internal medicine at National Taiwan University College of Medicine in Taipei, Taiwan, told Endocrine Today. “The is the first population-based observational study that showed a significant risk reduction for varicose veins associated with metformin use in [people with] type 2 diabetes.”

Tseng used the Taiwan National Health Insurance database to identify 138,805 adults diagnosed with diabetes between 1999 and 2005. The database provided records of diagnoses of diabetes and varicose veins as well as prescriptions for metformin during a follow-up period that ended Dec. 31, 2011.

Among the total study population, 123,710 individuals had used metformin and 15,095 had not. When comparing these groups, Tseng found that varicose veins occurred at a rate of 191.36 per 100,000 person years among those who did not use metformin and 110.04 per 100,000 person years among those who did (P = .01). Using metformin reduced the chances of developing varicose veins by 43% (HR = 0.57; 95% CI, = 0.47-0.69) compared with not using the medication. More sustained use improved these odds, with a 45% reduction for those on metformin for between 26.3 and 58 months (HR = 0.55; 95% CI, 0.44-0.69) and a 71% reduction for those taking metformin for more than 58 months (HR = 0.29; 95% CI, 0.23-0.37).

Metformin Adobe 2019 
Use of metformin appeared to reduce the risk for varicose veins among adults with type 2 diabetes.
Source: Adobe Stock

To account for potential changes in diabetes treatment, Tseng also examined several subgroups. When assessing participants who did not receive incretin-based therapy, those who took metformin were 37% less likely to develop varicose veins than those not taking metformin (HR = 0.63; 95% CI, 0.52-0.77). Participants who first appeared in the database between 1999 and 2002 were 44% less likely to have varicose veins if they took metformin compared with those who never took the medication (HR = 0.56; 95% CI, 0.42-0.74). Similarly, participants who first appeared in the database between 2003 and 2005 were 43% less likely to have varicose veins if they took metformin vs. never taking it (HR = 0.57; 95% CI, 0.44-0.75). 

In addition to comparing those taking metformin and those not taking the medication in the entire study population, Tseng created two groups for comparison via propensity score matching. Among 15,088 participants who had taken metformin (mean age, 67.62 years; 42.93% women), there was a 40% reduction in varicose vein risk (HR = 0.6; 95% CI, 0.45-0.8) compared with 15,088 matched participants who did not take metformin (mean age, 67.85 years; 42.77% women). The risk was particularly low for those who took metformin for more than 57.3 months (HR = 0.24; 95% CI, 0.13-0.42).

Similarly to the unmatched comparison, matched participants taking metformin were less likely to develop varicose veins than those not taking the medication even when including only those who first appeared in the database between 1999 and 2002 (HR = 0.62; 95% CI, 0.42-0.9) and those first appearing in the database between 2003 and 2005 (HR = 0.55; 95% CI, 0.35-0.86) as well as when incretin users were left out of the analysis (HR = 0.63; 95% CI, 0.52-0.77), according to Tseng.

“This study supports a reduced risk of varicose veins in type 2 diabetes patients who have been treated with metformin. However, confirmation is necessary,” Tseng wrote. “Because metformin is a cheap and safe drug that does not cause hypoglycemia when used as a monotherapy, its protection against varicose veins is worthy of more investigation.” – by Phil Neuffer

Disclosures: Tseng reports no relevant financial disclosures.