Serum folate levels and fatality among diabetic adults: A 15-y follow-up study of a national cohort

Objective: Folate is involved in carbohydrate metabolism, a process that can have clinical implications regarding diabetes management. The aim of this study was to assess the relationship between serum folate and fatality among adults with diabetes. Methods: A retrospective cohort study was conducted with 532 adults with diabetes who participated in Phase II of NHANES III (National Health and Nutrition Examination Survey III; 19911994). This study served as baseline and was linked to the National Death Index database for a 15-y (1991-2006) follow-up study. Estimates of hazard ratios (HRs) for all-cause and cancer-related deaths, cardiovascular disease (CVD), and diabetes for individuals with different serum folate levels were obtained from Cox proportional hazards regression. Results: The mean age of adults with diabetes and detected serum folate at baseline was 63.2 y (SD 13.8 y). During follow-up, diabetes was listed as a contributor for 138 of 299 deaths. For all-cause deaths, the fatality rate of the upper quartile (74.30/1000 person-years [PY]) was almost twofold higher than the lower quartile (41.75/1000 PY) of serum folate levels. After adjusting for several covariates, including serum vitamin B-12, cotinine, homocysteine and CVD history at baseline; the HRs for all-cause fatalities were 1.00 (reference), 1.62 (95% confidence interval [CI], 1.06-2.47) and 1.76 (95% CI, 1.09-2.83) among adults with diabetes in the lower, intermediate, and upper quartiles of serum folate levels, respectively. Conclusion: Results indicate that high serum folate concentrations are associated with an increased fatality risk among adults with diabetes. Further studies are warranted to determine the mechanism(s) of this phenomenon. (C) 2016 Elsevier Inc. All rights reserved.