Study design

This cross-sectional study was conducted on the elderly with and without nursing care in Isfahan, Iran in 2017. Inclusion criteria were: non-smoking, age over 60 years, and no vitamin D supplementation. The elderly with care were selected from the elderly living in the centers and the elderly without care from the elderly referring to the center at the beginning of the entry. Overall, according to the sample size calculation with 95% confidence level, 152 elderly people were enrolled in the study, all of whom completed the consent form. This study was approved by the Ethics Committee of Isfahan University of Medical Sciences (Ir.mui.rec. 1395.1.200).