Vitamin B12 and Risk of Diabetes: New insight from Cross-Sectional and Longitudinal Analyses of the China Stroke Primary Prevention Trial (CSPPT)

Introduction Previous studies in mostly Western populations, have yielded conflicting findings on the association of vitamin B12 with diabetes risk, in part, due to differences in study design and population characteristics. This study sought to examine the vitamin B12 and diabetes association in Chinese hypertensive adults by both cross-sectional and longitudinal analyses. Research Design and Methods This report included a total of 16699 participants from the China Stroke Primary Prevention Trial (CSPPT), with pertinent baseline and follow-up data. Diabetes mellitus (DM) was defined as either physician-diagnosed diabetes, the use of glucose-lowering drugs, or fasting blood glucose (FBG) ≥7.0 mmol/L. New-onset diabetes was defined as any new case of onset diabetes during the follow-up period or fasting blood glucose (FBG) ≥7.0 mmol/L at the exit visit. Results At baseline, there were 1872 (11.2%) diabetic patients; less than 1.5% had clinical B12 deficiency (<148.0 pmol/L). Over a median follow-up period of 4.5 years, there were 1589 (10.7%) cases of new-onset diabetes. Cross-sectional analyses showed a positive association between baseline vitamin B12 levels and FBG levels (β=0.18, 95%CI 0.15-0.21) and diabetes (OR=1.42, 95%CI 1.33-1.51). However, longitudinal analyses showed no association between baseline vitamin B12 and new-onset diabetes or changes in FBG levels. Among a subset of the sample (N=4366) with both baseline and exit B12 measurements, we found a positive association between an increase in B12 and an increase in FBG. Conclusions In this large Chinese hypertensive population mostly sufficient with vitamin B12, parallel cross-sectional and longitudinal analyses provided new insight into the conflicting findings of previous studies, and these results underscore the need for future studies to consider both baseline vitamin B12 and its longitudinal trajectory in order to better elucidate the role of vitamin B12 in the development of diabetes. Such findings, would have important clinical and public health implications.