title: Plasma calcium and risk of hypertension: propensity score analysis using data from the korean genome and epidemiology study.
abstract: OBJECTIVE
  To investigate associations between plasma calcium and future incidence of hypertension in a healthy population.
  
  
  METHODS
  We used prospective data from Ansung and Ansan cohorts (n = 10,038) of the Korean Genome and Epidemiology Study. Data from baseline (2001-02) to the fourth study (2007-08) were used. After excluding hypertensive cases at baseline, missing data, and outliers, 5560 participants were analyzed. Propensity scores for having higher plasma calcium (≥2.37 mmol/L) were created for each participant. After propensity score matching (1:1 nearest neighbor matching within caliper), 2153 pairs were left for analysis. Factors that were significantly different between the lower and higher plasma calcium groups before matching either became nonsignificant or the difference decreased in size.
  
  
  RESULTS
  Using multivariable Cox proportional hazard models with robust standard errors accounting for clustering of matched pairs, higher plasma calcium was associated with higher incidence of hypertension (adjusted HR, 1.24; robust 95%CI, 1.07-1.43). Among those with higher plasma calcium, low dietary calcium intake increased the development of hypertension, but the effect was not significant. Sensitivity analysis showed that our results were robust to hidden bias.
  
  
  CONCLUSIONS
  Plasma calcium was positively associated with incidence of hypertension. These results expand on cross-sectional associations between hypercalcemia and the metabolic syndrome, and extend the link to future risk of hypertension.
authors.affiliation: Division of Epidemiology and Health Index, Korea National Institute of Health, Osong, Korea ; Department of Gastroenterology, Asan Medical Center, Seoul, Korea.
authors.forename: Jong Wook
authors.initials: JW
authors.lastname: Kim
authors.forename: Kwang-Pil
authors.initials: KP
authors.lastname: Ko
authors.forename: Hee Jo
authors.initials: HJ
authors.lastname: Koo
authors.forename: Younjhin
authors.initials: Y
authors.lastname: Ahn
authors.forename: Seon-Joo
authors.initials: SJ
authors.lastname: Park
authors.forename: Hyo-Mi
authors.initials: HM
authors.lastname: Kim
authors.forename: Yeonjung
authors.initials: Y
authors.lastname: Kim
authors.forename: Sung Soo
authors.initials: SS
authors.lastname: Kim
keywords: hypertension; plasma calcium; propensity scores