Association between Vitamin D Status and Physical Function in the Severely Obese
Endocr Rev, Vol. 33 (03_MeetingAbstracts): MON-358
Copyright © 2012 by The Endocrine Society ENDO 2012: June 23-26, 2012, Houston, Texas
Aftab Khattak, MBBS1,2, Tomas Ahern, MB, BCh, BAO1,2,4, Emer O'Malley, BSc1, Dunlevy Colin, BSc, PhD1, Kilbane Mark, BSc, PhD3, Donal O'Shea, MB, BCh, BAO, MD1,2,4 and McKenna Malachi, MB, BCh, BAO, MD3,4
1 Department of Endocrinology, St Columcille's Hospital Loughlinstown, Ireland
2 Obesity Research Group, St Vincent's University Hospital Elm Park, Ireland
3 Metabolism Laboratory, St Vincent's University Hospital Elm Park, Ireland
4 Department of Endocrinology, St Vincent's University Hospital Elm Park, Ireland
Introduction Severe obesity (BMI>40kg/m2) has increased five-fold in prevalence over the past 15 years in the USA. Vitamin D deficiency is associated with physical dysfunction in the elderly. Obese people commonly have low serum 25hydroxyvitamin D (25OHD) due to sequestration in adipose tissue or reverse causation. We tested the hypothesis that poor vitamin D status is associated with physical inactivity and physical dysfunction in severely obese people.
Methods We determined 25OHD concentrations, recorded the hours per week spent exercising and measured the times taken to complete tests of physical function in 254 severely obese people. The tests consisted of ascending and descending a step 50 times and walking 500 m.
Based on the recent Institute of Medicine report we defined vitamin D status as follows: at risk of deficiency (25OHD <30 nmol/L); within range of requirement (25OHD 30-50 nmol/L); and above sufficiency limit (25OHD 50 nmol/L). Mann-Whitney U, Kruskall-Wallis and Spearman analyses were performed. Data are presented as means ±SD and correlation coefficients (r).
Results The average 25OHD and BMI for the entire cohort were 35.9±15.1 nmol/L and 51.1±8.4 kg/m2 respectively. 72.5% completed the 500m walk test and 81.0% the 50 step test. Serum 25OHD was higher in 50 step test completers (36.8±13.9 nmol/L) than in non-completers (29.7±13.0 nmol/L, p=0.003).Forty percent were at risk of being deficient, 40% were within range of requirement and 20% were above the sufficiency limit.
Weekly exercise time increased with improving vitamin D status: 1.4±2.5, 1.4±2.0 and 3.1±3.4 hours respectively (p=0.008). In test completers 500 m walk time decreased with improving vitamin D status: 7.0±1.4, 6.8±1.1 and 6.3±1.1 minutes respectively (p<0.001).
Similarly 50 step time decreased with improving vitamin D status: 124±29, 113±25 and 114±23 seconds respectively (p=0.039).
Serum 25OHD correlated significantly with exercise time (r=0.17, p=0.02), with 500 m walk time (r=-0.37, p<0.001) and with 50 step time (r=-0.16, p=0.04).
Conclusions In this cohort of severely obese people the prevalence of hypovitaminosis D was 40%. Vitamin D status had a strong relationship with physical inactivity and physical dysfunction in the severely obese. We conclude that vitamin D deficiency may contribute toward the risk of obesity related complications and suggest that studies exploring the effects of vitamin D supplementation in this cohort are warranted.
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