Propensity Score Matching to Determine the Impact of Metformin on All-Cause Mortality in Older Veterans with Diabetes Mellitus.

OBJECTIVES: To determine whether metformin is associated with reduced all-cause mortality in older adults with diabetes mellitus as compared with insulin or sulfonylureas, and to evaluate whether the metformin cumulative exposure followed a dose-response relation. METHODS: Retrospective cohort study with propensity score matching in veterans 65 years old and older with diabetes mellitus. Patients who had new prescriptions for metformin were matched for demographic and clinical factors with patients receiving new prescriptions for insulin or sulfonylureas using propensity score matching. All-cause mortality risks were compared between metformin and insulin/sulfonylureas using multivariate Cox regression models. A similar approach was used for tertiles of cumulative metformin doses. RESULTS: A sample of 174 veterans taking metformin was matched with 174 who took insulin/sulfonylureas. Most patients were men (97.4%), White (80.45%), and their mean ± standard deviation age was 69.15 ± 7.65 years. Metformin exposure was associated with reduced risk of all-cause mortality (hazard ratio 0.57, 95% confidence interval 0.39-0.84, P = 0.005). The upper tertile of cumulative metformin exposure was associated with lower all-cause mortality in the fully adjusted model (hazard ratio 0.28, 95% confidence interval 0.10-0.77, P = 0.013). CONCLUSIONS: This propensity matching study shows that metformin exposure is associated with a lower risk of all-cause mortality. Higher metformin cumulative exposure seems to reduce the risk of all-cause mortality in older veterans with diabetes mellitus.

The association of health literacy domains with hospitalizations and mortality.

OBJECTIVES: To determine whether health literacy, numeracy, and graph literacy are associated with all-cause hospitalizations or mortality in community-dwelling veterans. STUDY DESIGN: Retrospective cohort study. METHODS: A total of 470 community-dwelling veterans underwent evaluations of health literacy, numeracy, and graph literacy with validated instruments in 2012 and were followed until 2018. At the end of follow-up, the associations with all-cause hospitalizations and mortality were determined with the Andersen-Gill model and Cox regression multivariate analysis, respectively. RESULTS: There were no associations of health literacy, numeracy, or graph literacy with all-cause hospitalization or mortality after multivariate adjustment. In subgroup analysis, subjective numeracy was associated with hospitalizations in African Americans. Higher objective and subjective numeracy were associated with future hospitalizations only for those with a history of hospitalization. Higher graph literacy was associated with lower mortality in those with a history of hospitalization. CONCLUSIONS: This study did not show associations of health literacy, numeracy, or graph literacy scores with lower risk of all-cause hospitalization or mortality. Further research is needed with random sampling in a broader spectrum of healthcare settings to better understand what roles health literacy, numeracy, and graph literacy might play in healthcare utilization and clinical outcomes.