Vitamin D status, parathyroid function and femoral bone density in an elderly Swedish population living at home.
The aim of this study was to determine vitamin D status and bone mineral density (BMD) in elderly, independent Scandinavians. A cross-sectional examination was conducted in a sample of 104 subjects (mean age 84.5 years), for possible correlations among anthropometric data, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, intact parathyroid hormone (PTH) and femoral neck BMD. Daily dietary calcium and vitamin D intakes were below the recommended levels. Five percent of the subjects were taking calcium, and 30% vitamin D supplements. Previous fragility fracture was reported in 30% of the men, and 55% of the women. Higher mean values of serum 25-hydroxyvitamin D (p = 0.03) and femoral neck BMD (p = 0.03) were recorded in subjects spending > or = 3 hours outdoors weekly. Independently of time spent outdoors, subjects taking daily supplements of vitamin D (on average 5 micrograms) had higher 25-hydroxyvitamin D (p < 0.001) levels, without significant changes in femoral neck BMD values. Serum levels of intact PTH (reference range 8-51 ng/L) were elevated in 41%, of which 5% had mild primary hyperparathyroidism. Serum levels of 25-hydroxyvitamin D (reference range 10-65 ng/mL) and 1,25-dihydroxyvitamin D (reference range 15-55 pg/mL) were below the reference ranges in 4% and 5% of the subjects, respectively. When serum levels of 25-hydroxyvitamin D were lower than approximately 30 ng/mL, the serum intact PTH values began to increase from a level of 43 pg/mL. This threshold most probably reflected a more relevant value of vitamin D insufficiency, indicating that 45% of our subjects rather than 4% actually had hypovitaminosis. Multiple regression analysis demonstrated femoral neck BMD to be significantly and positively associated with higher body mass index, male gender, no history of fragility fracture and 25-hydroxyvitamin D (R2 = 0.39). It is concluded that in this sample of healthy elderly people who regularly spend time outdoors, vitamin D levels leading to secondary hyperparathyroidism seem to be a major cause of osteoporosis. Correcting chronic dietary calcium deficiency is likely to eliminate another factor contributing to poor bone health.
Melin
A L
AL
Department of Primary Health Care, Research and Development Unit, Serafen, Stockholm, Sweden.
Wilske
J
J
Ringertz
H
H
Sääf
M
M
D015502:Absorptiometry, Photon; D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D015992:Body Mass Index; D015519:Bone Density; D002136:Calcium, Dietary / Q000008:administration & dosage; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging; D016852:Housing for the Elderly; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010280:Parathyroid Glands / Q000502:physiology*; D013472:Sunlight; D013548:Sweden; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood
D002136:Calcium, Dietary; D014807:Vitamin D; C104450:25-hydroxyvitamin D