Plasma Magnesium Concentrations and Risk of Incident Cancer in Adults with Hypertension: A Nested Case-Control Study

Objective: The association between plasma magnesium and risk of incident cancer remains inconclusive in previous studies. We aimed to investigate the prospective relationship of baseline plasma magnesium concentrations with the risk of incident cancer and to examine possible effect modifiers. Methods: A nested case-control study with 228 incident cancer cases and 228 matched controls was conducted using data from the China Stroke Primary Prevention Trial (CSPPT), a randomized, double-blind, controlled trial, conducted from May 2008 to August 2013. Study outcomes included incident cancer and its subtypes. Results: When plasma magnesium concentrations were assessed as quartiles, a significantly higher incident risk of total cancer was found in participants in quartile 1 (<0.76 mmol/L; odds ratio [OR] = 2.70; 95% CI: 1.33-5.49) and quartile 4 (≥0.89 mmol/L; OR = 2.05; 95% CI: 1.12-3.76), compared with those in quartile 3 (0.83 to <0.89 mmol/L). In cancer site-specific analyses, similar trends were found for gastrointestinal cancer, esophageal cancer, gastric cancer, breast cancer, lung cancer, and other cancers. Furthermore, none of the variables, including age, sex, current smoking status, current alcohol intake, BMI, systolic blood pressure, and total cholesterol levels at baseline significantly modified the association between plasma magnesium and cancer risk. Conclusions: Both low and high plasma magnesium concentrations were significantly associated with an increased incident risk of cancer, compared with the reference concentrations of 0.83 to <0.89 mmol/L among hypertensive adults.