Can Vitamin D3 Improve Cognitive Function in Individuals With Type 2 Diabetes? (THINK-D)

Study Aims Diabetes increases the risk of cognitive dysfunction. The incidence of dementia is 1.5 to 2.5 times higher in persons with diabetes than the general population (1). There is evidence that cognitive decline significantly impacts the ability to self-manage diabetes (2). Strategies to prevent cognitive decline in persons with diabetes has not been well studied. A recent study reported that in persons who had vitamin D deficiency, the risk for all-cause dementia and Alzheimer's was doubled (3). Vitamin D receptors are located in the brain, and deficiency of vitamin D has been reported to negatively affect the development of brain and impact both growth factor signaling and neural activity (4, 5). Therefore, providing vitamin D supplementation to improve cognitive function in persons with diabetes who are at great risk for this comorbid condition is important. The investigators propose a small, randomized controlled trial to determine the effects of vitamin D3 supplementation in persons with type 2 diabetes who have symptoms of cognitive impairment. Persons will be randomized to receive either weekly vitamin D3 supplementation (50,000 IUs) or a matching comparator (5000 IUs) for a period of three months. Primary Aim: To determine the effect of vitamin D3 supplementation on cognitive function for persons with type 2 diabetes. Primary Hypothesis: Persons receiving weekly vitamin D3 supplementation (50,000 IUs) will have improved cognitive function compared to those receiving the comparator (5000 IUs) at three months. Secondary Aim: To determine the effect of vitamin D3 supplementation on diabetes self-management. Secondary Hypothesis: Persons receiving weekly vitamin D3 supplementation (50,000 IUs) will have improved self-management compared to those receiving the comparator (5000 IUs) at three months. The importance of this study is several fold. Vitamin D supplementation is a low cost intervention (6), it has minimal side effects (7), and it could have high impact for persons with type 2 diabetes who suffer from cognitive impairment which can significantly affect their diabetes self-management.