Bae JB, Han JW, Song J, et al. - Experts aspired to explore whether hypohomocysteinemia, like hyperhomocysteinemia, could increase the risk of dementia and Alzheimer disease (AD) in a large population-based cohort of older adults. From 2010 to 2018, this prospective cohort study followed 2,655 randomly selected community-dwelling, non-demented individuals aged 60 or older. Using Cox proportional hazards models, the authors measured baseline serum total homocysteine (tHcy) levels and investigated the effect of serum tHcy on the risks of dementia and AD. Dementia and AD developed in 85 and 64 participants during the follow-up period (mean = 5.4 years, SD = 0.9). In older adults, both hyperhomocysteinemia and hypohomocysteinemia increased the risk of dementia and AD. The risk of dementia related to vitamin supplement overuse or misuse should be recognized, and homocysteine-lowering health strategies should be adapted to account for dementia concerns associated with hypohomocysteinemia.