Vitamin D Deficiency in Elderly With Diabetes Mellitus Type 2: A Review

Diabetes mellitus type 2 (T2DM) is an emerging public health issue with high prevalence among older adults (>60 years old). Taking into consideration the great increase in the elderly population (approximately 7.5 billion worldwide), we can easily understand the impact of this chronic disease and its complications. On the other hand, vitamin D deficiency (VDD) is also a serious public health problem with significant impacts and multiple health effects. The correlation between DM and VDD has been suggested and established from many observational studies, reviews, and meta-analyses. The literature in PubMed and Google Scholar was searched for relevant articles published up to October 2020. The keywords used were the following: vitamin D deficiency, elderly, and diabetes mellitus type 2. Among the 556 articles retrieved, 90 full texts were eligible and only 34 studies (12 retrospective studies, two prospective cohorts, three meta-analyses, seven cross-sectional studies, nine randomized control trials (RCTs), and one observational study) met the inclusion criteria for the review. The author's name, year of publication, country, type of study, and the number of patients were reported. According to this review there is adequate evidence to support the correlation between VDD and T2DM in the elderly. The results from the RCTs are more conflicting and more studies are needed to confirm the impact of vitamin D deficiency (VD) supplementation on metabolic and lipid profile, oxidative stress, and the complications of T2DM in older patients. VDD is clearly related with severe retinopathy, diabetic peripheral neuropathy, and poor cognition performance, while there is consensus about the beneficial effect of VD on peripheral artery disease, foot ulceration prevention, and wound healing. On the other hand, there is controversy about the effect of VD supplementation on cardiovascular adverse events, endothelial function, and estimated glomerular filtration rate (eGFR). Finally, the association of VDD with fragility fractures and depression in the elderly with T2DM is currently insufficiently studied and remains controversial.