For millions of women, calcium supplements are part of a daily routine meant to protect aging bones and lower fracture risk. But research linking calcium supplements dementia risk in certain women has raised difficult questions, especially for those with vascular disease or a history of stroke. A widely discussed study found that older women with cerebrovascular disease who used calcium supplements faced a significantly higher likelihood of developing dementia compared with similar women who did not supplement. That does not mean every calcium pill is dangerous, but it does suggest that personal health history matters more than many people realize.