Serum calcium and incident diabetes: a retrospective study in Hong Kong Chinese and a meta-analysis

Abstract

BACKGROUND: Serum calcium and its metabolism play an important role in glucose metabolism, whether serum calcium and calcium intake can predict diabetes remains largely unknown. We aimed to evaluate the association of serum calcium with incident diabetes. METHODS: We conducted a retrospective cohort study on 1702 male and 4394 female Southern Chinese aged 20 years or above free of diabetes at baseline. We also searched PubMed, MEDLINE, and Cochrane library in September 2014 to identify observational studies accessing the association between elevated serum calcium and incident diabetes. The overall relative risks (RRs) were calculated using fixed-effect model with inverse variance method. RESULTS: In 59 130.9 person-years of follow-up, 631 participants developed diabetes. Serum total calcium (third quartile: hazard ratio [HR]=1.42; 95% confidence interval [CI], 1.12-1.8; highest quartile: HR=1.42; 95% CI, 1.11- 1.79; as compared to the lowest quartile) was significantly associated with incident diabetes. Addition of serum total calcium to age, sex, and body mass index (BMI) significantly improved integrated discrimination and category-less net reclassification index. Significant interactions with BMI and age were observed. Greater total calcium intake was significantly associated with lower incident diabetes (comparing extreme quartile, HR=0.78; 95% CI, 0.61-0.98). In meta-analysis, two studies together with our results were included, the total participants were 34 117 and the pooled RR was 1.43 (95% CI, 1.20-1.70) comparing individuals of high serum calcium level who had incident diabetes to those who did not have. CONCLUSIONS: Elevated serum total calcium and probably lower total calcium intake were associated with incident diabetes. Adding serum total calcium to basic clinical risk factors significantly improved risk prediction. The mechanism warrants further investigation.