Among older adults navigating the uncertain terrain between normal aging and dementia, a small but striking study suggests that something as humble as a daily vitamin may carry unexpected weight. Researchers at Emory University found that participants with mild cognitive impairment and disrupted sleep who took at least 5,000 IU of vitamin D daily scored meaningfully higher on standard cognitive assessments — a finding that points not to a cure, but to a window, a moment in the arc of cognitive decline when the brain may still be reachable. The study, published in Sleep Medicine, does not yet p