Low Vitamin D Levels Do Not Predict Hyperglycemia in Elderly Endurance Athletes (but in Controls).
OBJECTIVE
Recent studies revealed a link between hypovitaminosis D3 and the risk for hyperglycemia. Further mechanistic and interventional investigations suggested a common reason for both conditions rather than a causal relationship. Exposure to sunlight is the most relevant source of vitamin D3 (25(OH)D), whereas adipose tissue is able to store relevant amounts of the lipophilic vitamin. Since running/bicycling leads to increased out-door time and alters physiological response mechanisms, it can be hypothesized that the correlation between hypovitaminosis D3 and hyperglycemia might be disturbed in outdoor athletes.


METHODS
47 elderly marathoners/bicyclists and 47 age/sex matched controls were studied in a longitudinal setting at baseline and after three years. HbA1c as a surrogate for (pre-)diabetic states was quantified via HPLC, 25(OH)D levels were measured by means of chemiluminescent assays. Physical performance was assessed by ergometry.


RESULTS
When adjusted for seasonal variations, 25(OH)D was significantly higher in athletes than in controls. 25(OH)D levels inversely correlated with triglycerides in both groups, whereas only in controls an association between high BMI or low physical performance with hypovitaminosis D3 had been found. Likewise, the presence of hypovitaminosis D3 at baseline successfully predicted hyperglycemia at the follow up examinations within the control group (AUC = 0.85, 95% CI [0.74, 0.96], p < .001, statistically independent from BMI), but not in athletes.


CONCLUSIONS
Our data suggest that mechanisms of HbA1c elevation might differ between athletes and controls. Thus, intense physical activity must be taken into account as a potential pre-analytic confounder when it is aimed to predict metabolic risk by vitamin D3 levels.
Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria.
Helmuth
http://orcid.org/0000-0003-4605-2503
H
Haslacher
Empirical Research, Vienna, Austria.
Sonja
S
Nistler
Department of Public Health, Medical University of Vienna, Vienna, Austria.
Delgerdalai
D
Batmyagmar
Empirical Research, Vienna, Austria.
Elisabeth
E
Ponocny-Seliger
Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria.
Thomas
T
Perkmann
Health and Prevention Center, Sanatorium Hera, Vienna, Austria.
Thomas M
TM
Scherzer
Department of Public Health, Medical University of Vienna, Vienna, Austria.
Michael
M
Kundi
Gruppenpraxis Labors.at, Vienna, Austria.
Georg
G
Endler
Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria.
Franz
F
Ratzinger
Division of Occupational Medicine, Medical University of Vienna, Austria.
Alexander
A
Pilger
Department of Laboratory Medicine, Medical University of Vienna, Vienna, Austria.
Oswald F
OF
Wagner
Health and Prevention Center, Sanatorium Hera, Vienna, Austria.
Robert
R
Winker
D000368:Aged; D056352:Athletes; D001642:Bicycling / Q000502:physiology; D015992:Body Mass Index; D002762:Cholecalciferol / Q000378:metabolism*; D016552:Ergometry; D015444:Exercise / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011446:Prospective Studies; D012372:ROC Curve; D012420:Running / Q000502:physiology; D012621:Seasons; D013997:Time Factors; D014808:Vitamin D Deficiency / Q000378:metabolism* / Q000503:physiopathology
D002762:Cholecalciferol; D006442:Glycated Hemoglobin