Objective: To study the influence of underweight, body composition and vitamin D deficiency on bone mineral density in patients with advanced pulmonary disease.
Design: Cross-sectional study with time span for inclusion set at 5 years.
Setting: The clinical work and biochemical analyses were carried out at Rikshospitalet University Hospital, Norway. Analyses for vitamin D metabolites and bone markers were carried out at Aker University Hospital, and bone measurements at Clinic of Osteoporosis.
Subjects: Seventy-one candidates for lung transplantation (63% chronic obstructive pulmonary disease, 42 underweight and 29 normal weight) were included.
Main outcome measures: Body composition, bone mineral density at lumbar spine and femur neck, serum concentration of calcidiol and vitamin D intake.
Results: Subnormal calcidiol levels were present in 52% of the underweight patients and 69% of the normal-weight patients. The resulting models of linear regression showed that for the lumbar spine T scores model, the total variation of 16.7% was explained by group (underweight/normal weight), sex and age. For the femur neck T scores model, the total variation of 20.4% was explained by the interaction of underweight and vitamin D deficiency (with borderline significance) and by arm muscle circumference percentage of standard. In patients with normal calcidiol levels, the median intake of vitamin D was 17 microg in the underweight patients and 11 microg in the normal-weight patients.
Conclusions: Vitamin D deficiency was common in both underweight and normal-weight patients, but only in the underweight patients, an association between vitamin D deficiency and reduced femur neck T scores was indicated.