High and low vitamin D level is associated with cardiovascular autonomic neuropathy in people with Type 1 and Type 2 diabetes

Aim To investigate the possible association between vitamin D deficiency and cardiovascular autonomic neuropathy in people with diabetes. Methods A total of 113 people with Type 1 or Type 2 diabetes [mean (interquartile range) diabetes duration 22.0 (12–31) years, mean (sd) age 56.2 (13.0) years, 58% men] underwent vitamin D (D2 and D3) assessment, and were screened for cardiovascular autonomic neuropathy using three cardiovascular reflex tests [heart rate response to deep breathing (E/I ratio), to standing (30/15 ratio) and to the Valsalva manoeuvre] and assessment of 5-min resting heart rate and heart rate variability indices. Results We found an inverse U-shaped association between serum vitamin D level and E/I ratio, 30/15 ratio and three heart rate variability indices (P