Comprehensive assessment on the association of dietary vitamins with all-cause and cardiovascular mortality among individuals with prediabetes: evidence from NHANES 1999–2018

Background Prediabetes has become a global health issue, and currently, the relationship between vitamin levels and mortality in prediabetes remains unclear. This study aims to investigate the association between the levels of eleven vitamins and all-cause and cardiovascular disease (CVD) mortality in prediabetes patients. Methods This cross-sectional study included 14634 prediabetes patients from 10 cycles of the National Health and Nutrition Examination Survey between 1999 and 2018. Mortality and underlying causes of death were determined by linking records from the National Death Index until December 31, 2019. Multivariable Cox proportional hazards regression models were established to assess hazard ratios and 95% confidence intervals for all-cause, CVD, cancer, and other mortalities. Restricted cubic splines were used to visualize non-linear associations between various vitamins and mortality risk. Results During the follow-up period, 2316/14634 prediabetes patients died (12.55%), with 722 deaths (3.68%) attributed to CVD. After multivariable adjustment, vitamin B1, niacin, folate, vitamin C, vitamin E, and vitamin K levels exhibited non-linear associations with all-cause mortality (all p<0.05). Vitamin B1, niacin, and vitamin E levels showed non-linear associations with CVD mortality (p<0.05. Vitamin B6 exhibited a linear negative association with all-cause, CVD, and other mortalities (p>0.05). However, vitamins A and B2 levels were not significantly associated with mortality rates (all p>0.05). Consistent results were observed in the subgroup analyses after complete adjustment for variables. Conclusions Higher levels of dietary vitamins B1, B6, niacin, folate, vitamin C, vitamin E, and vitamin K were significantly associated with lower risk of all-cause mortality and CVD mortality in patients with prediabetes. There was no association between vitamin A and B2 levels and all-cause and CVD mortality among individuals with prediabetes. These findings suggest the importance of correcting vitamin deficiencies to prevent mortality in prediabetes patients.