Vitamin D has been known for many years to play a critical role in skeletal health, such that very low levels of this hormone (<20 nmol/L) can cause osteomalacia, a disorder of impaired bone mineralization.1 More recently, observational studies have reported inverse associations between levels of serum 25-hydroxyvitamin D (25[OH]D), the metabolite that best reflects overall vitamin D status, and the risk of a wide range of diseases, including cancer, vascular disease, infectious conditions, autoimmune diseases, osteoporosis, type 2 diabetes mellitus, and obesity.1 In this issue of the Archives, Llewellyn et al2 report that, in a prospective cohort study of 858 Italian adults 65 years and older, baseline levels of serum 25(OH)D were inversely related to the rate of cognitive decline during a median follow-up of 6 years. This effect was most apparent in participants with the lowest levels of 25(OH)D (<25 nmol/L) and persisted after adjusting for several potential confounding variables. Thus, accelerated cognitive decline is now added to the list of conditions that have been associated with lower levels of vitamin D.
Grey A, Bolland M. Vitamin DA Place in the Sun?. Arch Intern Med. 2010;170(13):1099-1100. doi:10.1001/archinternmed.2010.174