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Study Overview
Objective. To assess whether metformin use is associated with lower risk of fatal or nonfatal major adverse cardiovascular events (MACE) as compared to sulfonylurea use among diabetic patients with reduced kidney function.
Design. Retrospective cohort study of US Veterans receiving care within the Veterans Health Administration, with data supplemented by linkage to Medicare, Medicaid, and National Death Index data from 2001 through 2016.
Setting and participants. A retrospective cohort of Veterans Health Administration (VHA) patients, aged 18 years and older. Pharmacy data included medication, date filled, days supplied, and number of pills dispensed. For Medicare and Medicaid patients, enrollees’ claims files and prescription (Part D) data were obtained. In addition, dates and cause of death were obtained from vital status and the National Death Index files.
Patients with new-onset type 2 diabetes were identified by selecting new users of metformin, glipizide, glyburide, or glimepiride. These patients were followed longitudinally and the date of cohort entry and start of follow-up was the day of reaching a reduced kidney function threshold, defined as either an estimated glomerular filtration rate (eGFR) of less than 60 mL/m
Main outcome measures. Primary outcome was the composite of MACE including hospitalization for acute myocardial infarction (AMI), ischemic or hemorrhagic stroke, transient ischemic attack (TIA), or date of cardiovascular death. The secondary outcome excluded TIA as part of the composite MACE event because not all patients who sustain a TIA are admitted to the hospital.
Main results. From January 1, 2002 through December 30, 2015, 67,749 new metformin users and 28,976 new sulfonylurea users who persisted with treatment were identified. After using propensity score-weighted matching, 24,679 metformin users and 24,799 sulfonylurea users entered the final analysis. Cohort patients were 98% male and 81.8% white. Metformin users were younger than sulfonylurea users, with a median age of 61 years versus 71 years, respectively.
For the main outcome, there were 1048 composite MACE events among metformin patients with reduced kidney function and 1394 MACE events among sulfonylurea patients, yielding 23.0 (95% confidence interval [CI], 21.7-24.4) versus 29.2 (95% CI, 27.7-30.7) events per 1000 person-years of use, respectively, after propensity score-weighting. After covariate adjustment, the cause-specific adjusted hazard ratio (aHR) for MACE was 0.80 (95% CI, 0.75-0.86) among metformin users compared with sulfonylurea users. The adjusted incidence rate difference was 5.8 (95% CI, 4.1-7.3) fewer events per 1000-person years for metformin compared with sulfonylurea users. Results were also consistent for each component of the primary outcome, including cardiovascular hospitalizations (aHR, 0.87; 95% CI, 0.80-0.95) and cardiovascular deaths (aHR, 0.70; 95% CI, 0.63-0.78).
Analysis of secondary outcomes, which included AMI, stroke, and cardiovascular death and excluded TIA, demonstrated similar results, with a cause-specific aHR of 0.78 (95% CI, 0.72-0.84) among metformin users compared with sulfonylurea users. The adjusted incidence rate difference was 5.9 (95% CI, 4.3-7.6) fewer events per 1000-person years for metformin compared with sulfonylurea users.
Conclusion. For patients with diabetes and reduced kidney function, treatment with metformin monotherapy, as compared with a sulfonylurea, was associated with a lower risk of MACE.
Commentary
There are approximately 30 million US adults with a diagnosis of type 2 diabetes (T2DM), of whom 20% also have impaired kidney function or chronic kidney disease (CKD).1 Metformin hydrochloride has remained the preferred first-line treatment for T2DM based on safety and effectiveness, as well as low cost.2 Metformin is eliminated by the kidneys and can accumulate as eGFR declines. Based on the negative clinical experience, the US Food and Drug Administration (FDA) issued a safety warning restricting metformin for patients with serum creatinine levels of 1.5 mg/dL or greater for men or 1.4 mg/dL or greater for women. The FDA recommended against starting metformin therapy in patients with CKD with eGFR between 30 and 45 mL/min/1.73 m2, although patients already taking metformin can continue with caution in that setting.1,3
There are several limitations in conducting observational studies comparing metformin to other glucose-lowering medications. First, metformin trials typically excluded patients with CKD due to the FDA warnings. Second, there is usually a time-lag bias in which patients who initiate glucose-lowering medications other than metformin are at a later stage of disease. Third, there is often an allocation bias, as there are substantial differences in baseline characteristics between metformin and sulfonylurea monotherapy users, with metformin users usually being younger and healthier.4
In this retrospective cohort study by Roumie et al, the authors used propensity score–weighted matching to reduce the impacts on time-lag and allocation bias. However, several major limitations remained in this study. First, the study design excluded those who began diabetes treatment after the onset of reduced kidney function; therefore, this study cannot be generalized to patients who already have reduced eGFR at the time of metformin initiation. Second, cohort entry and the start of follow-up was either an elevated serum creatinine or reduced eGFR less than 60 mL/min/1.73 m2. The cohort may have included some patients with an acute kidney injury event, rather than progression to CKD, who recovered from their acute kidney injury. Third, the study population was mostly elderly white men; together with the lack of dose analysis, this study may not be generalizable to other populations.
Applications for Clinical Practice
The current study demonstrated that metformin use, as compared to sulfonylureas, has a lower risk of fatal or nonfatal major adverse cardiovascular events among patients with reduced kidney function. When clinicians are managing hyperglycemia in patients with type 2 diabetes, it is important to keep in mind that all medications have adverse effects. There are now 11 drug classes for treating diabetes, in addition to multiple insulin options, and the challenge for clinicians is to present clear information to guide patients using shared decision making, based on each patient’s clinical circumstances and preferences, to achieve individualized glycemic target ranges.
–Ka Ming Gordon Ngai, MD, MPH
1. Geiss LS, Kirtland K, Lin J, et al. Changes in diagnosed diabetes, obesity, and physical inactivity prevalence in US counties, 2004-2012. PLoS One. 2017;12:e0173428.
2. Good CB, Pogach LM. Should metformin be first-line therapy for patients with type 2 diabetes and chronic kidney disease? JAMA Intern Med. 2018;178:911-912.
3. US Food and Drug Administration. FDA revises warnings regarding use of the diabetes medicine metformin in certain patients with reduced kidney function. https://www.fda.gov/downloads/Drugs/DrugSafety/UCM494140.pdf. Accessed September 30, 2019.
4. Wexler DJ. Sulfonylureas and cardiovascular safety the final verdict? JAMA. 2019;322:1147-1149.
Study Overview
Objective. To assess whether metformin use is associated with lower risk of fatal or nonfatal major adverse cardiovascular events (MACE) as compared to sulfonylurea use among diabetic patients with reduced kidney function.
Design. Retrospective cohort study of US Veterans receiving care within the Veterans Health Administration, with data supplemented by linkage to Medicare, Medicaid, and National Death Index data from 2001 through 2016.
Setting and participants. A retrospective cohort of Veterans Health Administration (VHA) patients, aged 18 years and older. Pharmacy data included medication, date filled, days supplied, and number of pills dispensed. For Medicare and Medicaid patients, enrollees’ claims files and prescription (Part D) data were obtained. In addition, dates and cause of death were obtained from vital status and the National Death Index files.
Patients with new-onset type 2 diabetes were identified by selecting new users of metformin, glipizide, glyburide, or glimepiride. These patients were followed longitudinally and the date of cohort entry and start of follow-up was the day of reaching a reduced kidney function threshold, defined as either an estimated glomerular filtration rate (eGFR) of less than 60 mL/m
Main outcome measures. Primary outcome was the composite of MACE including hospitalization for acute myocardial infarction (AMI), ischemic or hemorrhagic stroke, transient ischemic attack (TIA), or date of cardiovascular death. The secondary outcome excluded TIA as part of the composite MACE event because not all patients who sustain a TIA are admitted to the hospital.
Main results. From January 1, 2002 through December 30, 2015, 67,749 new metformin users and 28,976 new sulfonylurea users who persisted with treatment were identified. After using propensity score-weighted matching, 24,679 metformin users and 24,799 sulfonylurea users entered the final analysis. Cohort patients were 98% male and 81.8% white. Metformin users were younger than sulfonylurea users, with a median age of 61 years versus 71 years, respectively.
For the main outcome, there were 1048 composite MACE events among metformin patients with reduced kidney function and 1394 MACE events among sulfonylurea patients, yielding 23.0 (95% confidence interval [CI], 21.7-24.4) versus 29.2 (95% CI, 27.7-30.7) events per 1000 person-years of use, respectively, after propensity score-weighting. After covariate adjustment, the cause-specific adjusted hazard ratio (aHR) for MACE was 0.80 (95% CI, 0.75-0.86) among metformin users compared with sulfonylurea users. The adjusted incidence rate difference was 5.8 (95% CI, 4.1-7.3) fewer events per 1000-person years for metformin compared with sulfonylurea users. Results were also consistent for each component of the primary outcome, including cardiovascular hospitalizations (aHR, 0.87; 95% CI, 0.80-0.95) and cardiovascular deaths (aHR, 0.70; 95% CI, 0.63-0.78).
Analysis of secondary outcomes, which included AMI, stroke, and cardiovascular death and excluded TIA, demonstrated similar results, with a cause-specific aHR of 0.78 (95% CI, 0.72-0.84) among metformin users compared with sulfonylurea users. The adjusted incidence rate difference was 5.9 (95% CI, 4.3-7.6) fewer events per 1000-person years for metformin compared with sulfonylurea users.
Conclusion. For patients with diabetes and reduced kidney function, treatment with metformin monotherapy, as compared with a sulfonylurea, was associated with a lower risk of MACE.
Commentary
There are approximately 30 million US adults with a diagnosis of type 2 diabetes (T2DM), of whom 20% also have impaired kidney function or chronic kidney disease (CKD).1 Metformin hydrochloride has remained the preferred first-line treatment for T2DM based on safety and effectiveness, as well as low cost.2 Metformin is eliminated by the kidneys and can accumulate as eGFR declines. Based on the negative clinical experience, the US Food and Drug Administration (FDA) issued a safety warning restricting metformin for patients with serum creatinine levels of 1.5 mg/dL or greater for men or 1.4 mg/dL or greater for women. The FDA recommended against starting metformin therapy in patients with CKD with eGFR between 30 and 45 mL/min/1.73 m2, although patients already taking metformin can continue with caution in that setting.1,3
There are several limitations in conducting observational studies comparing metformin to other glucose-lowering medications. First, metformin trials typically excluded patients with CKD due to the FDA warnings. Second, there is usually a time-lag bias in which patients who initiate glucose-lowering medications other than metformin are at a later stage of disease. Third, there is often an allocation bias, as there are substantial differences in baseline characteristics between metformin and sulfonylurea monotherapy users, with metformin users usually being younger and healthier.4
In this retrospective cohort study by Roumie et al, the authors used propensity score–weighted matching to reduce the impacts on time-lag and allocation bias. However, several major limitations remained in this study. First, the study design excluded those who began diabetes treatment after the onset of reduced kidney function; therefore, this study cannot be generalized to patients who already have reduced eGFR at the time of metformin initiation. Second, cohort entry and the start of follow-up was either an elevated serum creatinine or reduced eGFR less than 60 mL/min/1.73 m2. The cohort may have included some patients with an acute kidney injury event, rather than progression to CKD, who recovered from their acute kidney injury. Third, the study population was mostly elderly white men; together with the lack of dose analysis, this study may not be generalizable to other populations.
Applications for Clinical Practice
The current study demonstrated that metformin use, as compared to sulfonylureas, has a lower risk of fatal or nonfatal major adverse cardiovascular events among patients with reduced kidney function. When clinicians are managing hyperglycemia in patients with type 2 diabetes, it is important to keep in mind that all medications have adverse effects. There are now 11 drug classes for treating diabetes, in addition to multiple insulin options, and the challenge for clinicians is to present clear information to guide patients using shared decision making, based on each patient’s clinical circumstances and preferences, to achieve individualized glycemic target ranges.
–Ka Ming Gordon Ngai, MD, MPH
Study Overview
Objective. To assess whether metformin use is associated with lower risk of fatal or nonfatal major adverse cardiovascular events (MACE) as compared to sulfonylurea use among diabetic patients with reduced kidney function.
Design. Retrospective cohort study of US Veterans receiving care within the Veterans Health Administration, with data supplemented by linkage to Medicare, Medicaid, and National Death Index data from 2001 through 2016.
Setting and participants. A retrospective cohort of Veterans Health Administration (VHA) patients, aged 18 years and older. Pharmacy data included medication, date filled, days supplied, and number of pills dispensed. For Medicare and Medicaid patients, enrollees’ claims files and prescription (Part D) data were obtained. In addition, dates and cause of death were obtained from vital status and the National Death Index files.
Patients with new-onset type 2 diabetes were identified by selecting new users of metformin, glipizide, glyburide, or glimepiride. These patients were followed longitudinally and the date of cohort entry and start of follow-up was the day of reaching a reduced kidney function threshold, defined as either an estimated glomerular filtration rate (eGFR) of less than 60 mL/m
Main outcome measures. Primary outcome was the composite of MACE including hospitalization for acute myocardial infarction (AMI), ischemic or hemorrhagic stroke, transient ischemic attack (TIA), or date of cardiovascular death. The secondary outcome excluded TIA as part of the composite MACE event because not all patients who sustain a TIA are admitted to the hospital.
Main results. From January 1, 2002 through December 30, 2015, 67,749 new metformin users and 28,976 new sulfonylurea users who persisted with treatment were identified. After using propensity score-weighted matching, 24,679 metformin users and 24,799 sulfonylurea users entered the final analysis. Cohort patients were 98% male and 81.8% white. Metformin users were younger than sulfonylurea users, with a median age of 61 years versus 71 years, respectively.
For the main outcome, there were 1048 composite MACE events among metformin patients with reduced kidney function and 1394 MACE events among sulfonylurea patients, yielding 23.0 (95% confidence interval [CI], 21.7-24.4) versus 29.2 (95% CI, 27.7-30.7) events per 1000 person-years of use, respectively, after propensity score-weighting. After covariate adjustment, the cause-specific adjusted hazard ratio (aHR) for MACE was 0.80 (95% CI, 0.75-0.86) among metformin users compared with sulfonylurea users. The adjusted incidence rate difference was 5.8 (95% CI, 4.1-7.3) fewer events per 1000-person years for metformin compared with sulfonylurea users. Results were also consistent for each component of the primary outcome, including cardiovascular hospitalizations (aHR, 0.87; 95% CI, 0.80-0.95) and cardiovascular deaths (aHR, 0.70; 95% CI, 0.63-0.78).
Analysis of secondary outcomes, which included AMI, stroke, and cardiovascular death and excluded TIA, demonstrated similar results, with a cause-specific aHR of 0.78 (95% CI, 0.72-0.84) among metformin users compared with sulfonylurea users. The adjusted incidence rate difference was 5.9 (95% CI, 4.3-7.6) fewer events per 1000-person years for metformin compared with sulfonylurea users.
Conclusion. For patients with diabetes and reduced kidney function, treatment with metformin monotherapy, as compared with a sulfonylurea, was associated with a lower risk of MACE.
Commentary
There are approximately 30 million US adults with a diagnosis of type 2 diabetes (T2DM), of whom 20% also have impaired kidney function or chronic kidney disease (CKD).1 Metformin hydrochloride has remained the preferred first-line treatment for T2DM based on safety and effectiveness, as well as low cost.2 Metformin is eliminated by the kidneys and can accumulate as eGFR declines. Based on the negative clinical experience, the US Food and Drug Administration (FDA) issued a safety warning restricting metformin for patients with serum creatinine levels of 1.5 mg/dL or greater for men or 1.4 mg/dL or greater for women. The FDA recommended against starting metformin therapy in patients with CKD with eGFR between 30 and 45 mL/min/1.73 m2, although patients already taking metformin can continue with caution in that setting.1,3
There are several limitations in conducting observational studies comparing metformin to other glucose-lowering medications. First, metformin trials typically excluded patients with CKD due to the FDA warnings. Second, there is usually a time-lag bias in which patients who initiate glucose-lowering medications other than metformin are at a later stage of disease. Third, there is often an allocation bias, as there are substantial differences in baseline characteristics between metformin and sulfonylurea monotherapy users, with metformin users usually being younger and healthier.4
In this retrospective cohort study by Roumie et al, the authors used propensity score–weighted matching to reduce the impacts on time-lag and allocation bias. However, several major limitations remained in this study. First, the study design excluded those who began diabetes treatment after the onset of reduced kidney function; therefore, this study cannot be generalized to patients who already have reduced eGFR at the time of metformin initiation. Second, cohort entry and the start of follow-up was either an elevated serum creatinine or reduced eGFR less than 60 mL/min/1.73 m2. The cohort may have included some patients with an acute kidney injury event, rather than progression to CKD, who recovered from their acute kidney injury. Third, the study population was mostly elderly white men; together with the lack of dose analysis, this study may not be generalizable to other populations.
Applications for Clinical Practice
The current study demonstrated that metformin use, as compared to sulfonylureas, has a lower risk of fatal or nonfatal major adverse cardiovascular events among patients with reduced kidney function. When clinicians are managing hyperglycemia in patients with type 2 diabetes, it is important to keep in mind that all medications have adverse effects. There are now 11 drug classes for treating diabetes, in addition to multiple insulin options, and the challenge for clinicians is to present clear information to guide patients using shared decision making, based on each patient’s clinical circumstances and preferences, to achieve individualized glycemic target ranges.
–Ka Ming Gordon Ngai, MD, MPH
1. Geiss LS, Kirtland K, Lin J, et al. Changes in diagnosed diabetes, obesity, and physical inactivity prevalence in US counties, 2004-2012. PLoS One. 2017;12:e0173428.
2. Good CB, Pogach LM. Should metformin be first-line therapy for patients with type 2 diabetes and chronic kidney disease? JAMA Intern Med. 2018;178:911-912.
3. US Food and Drug Administration. FDA revises warnings regarding use of the diabetes medicine metformin in certain patients with reduced kidney function. https://www.fda.gov/downloads/Drugs/DrugSafety/UCM494140.pdf. Accessed September 30, 2019.
4. Wexler DJ. Sulfonylureas and cardiovascular safety the final verdict? JAMA. 2019;322:1147-1149.
1. Geiss LS, Kirtland K, Lin J, et al. Changes in diagnosed diabetes, obesity, and physical inactivity prevalence in US counties, 2004-2012. PLoS One. 2017;12:e0173428.
2. Good CB, Pogach LM. Should metformin be first-line therapy for patients with type 2 diabetes and chronic kidney disease? JAMA Intern Med. 2018;178:911-912.
3. US Food and Drug Administration. FDA revises warnings regarding use of the diabetes medicine metformin in certain patients with reduced kidney function. https://www.fda.gov/downloads/Drugs/DrugSafety/UCM494140.pdf. Accessed September 30, 2019.
4. Wexler DJ. Sulfonylureas and cardiovascular safety the final verdict? JAMA. 2019;322:1147-1149.