China: A retrospective cohort study from Hong Kong has found that calcium supplementation alone may increase the risk of recurrent cardiovascular events in individuals with established cardiovascular disease (CVD). However, this increased risk was not observed when calcium was combined with vitamin D, suggesting a potential protective or mitigating role of vitamin D. Overall, the findings do not support the cardiovascular safety of calcium supplementation alone in patients with pre-existing CVD. The study, published in the Journal of the American Heart Association, was led by Xiaowen Zhang from the Department of Pharmacology and Pharmacy, The University of Hong Kong. It aimed to clarify the long-debated relationship between calcium supplement use and cardiovascular outcomes, particularly in individuals already diagnosed with major cardiovascular conditions.For this purpose, the researchers conducted a large population-based retrospective cohort study involving individuals aged 40 years or older who were newly diagnosed with CVD between 2006 and 2015. Patients prescribed calcium supplements were compared with those who had never received such prescriptions. Using propensity score matching to ensure comparable baseline characteristics, the study included 17,720 patients in each group. Statistical analysis was performed using Cox proportional hazard models to estimate the risk of recurrent cardiovascular events. The following were the key findings:Calcium supplementation was associated with a modest but statistically significant increase in the risk of recurrent cardiovascular events.Patients using calcium supplements had a higher likelihood of CVD-related hospitalizations or emergency department visits.The increased risk was more pronounced with calcium-only supplementation.No similar increase in risk was observed when calcium was combined with vitamin D.The association between calcium supplementation and recurrent cardiovascular events was stronger in men than in women.These findings indicate potential sex-based differences in cardiovascular risk related to supplement use.The study adds to growing evidence suggesting that calcium supplementation, particularly when used without vitamin D, may not be as safe as previously assumed in high-risk populations. While calcium is commonly prescribed for bone health, especially in older adults, its potential cardiovascular implications warrant careful consideration.The authors emphasized that clinicians should exercise caution when recommending calcium supplements to patients with established cardiovascular disease. The combination of calcium with vitamin D may represent a safer alternative, although further research is needed to confirm this observation.Overall, the study highlights the importance of individualized treatment decisions, particularly in patients with pre-existing cardiovascular conditions. It also highlights the need for clinicians to balance the benefits of calcium supplementation for bone health against its potential risks for cardiovascular outcomes.Reference: https://doi.org/10.1161/JAHA.125.047455