1. Vitamin D Inadequacy is Highly Prevalent Among North American Women Treated for Osteoporosis MF Holick1, ES Siris2, N Binkley3, MK Beard4, AA Khan5, JT Katzer6, E Chen6, AE de Papp6 1Boston University Medical Center, Boston, MA, 2Columbia University, NY, NY, 3University of Wisconsin, Madison, WI, 4University of Utah, Salt Lake City, UT, 5McMaster University, Hamilton, ON, 6Merck & Co., Inc., West Point, PA
Table 1. BASELINE CHARACTERISTICS
INTRODUCTION
RESULTS
Characteristics
Total
N = 1536
Age (years) Mean (SD)
71.1 (9.9)
Race n (%)
Caucasian
Black
Asian
Other
1406 (91.5)
41 (2.7)
32 (2.1)
18 (1.2)
Body Mass Index (kg/m2) Mean (SD)
26.4 (5.5)
Geographic Region by Latitude n (%)
≥42º
35º - 41º
<35º
532 (34.6)
642 (41.8)
362 (23.6)
Vitamin D Supplementation n (%)
<400 IU Daily
≥400 IU Daily
622 (40.5)
914 (59.5)
T-score Mean (SD)
Lumbar Spine
Total Hip
-1.8 (1.5)
-1.7 (1.0)
SD=standard deviation. IU=international units.
Vitamin D inadequacy can lead to alterations in calcium and and phosphate homeostasis, secondary hyperparathyroidism, bone loss, osteoporosis, and an increase risk of fractures.
Vitamin D inadequacy may be overlooked by clinicians, potentially leading to a lack of adequate vitamin D supplementation in patients treated for osteoporosis.
This study was designed to evaluate the distribution of serum 25(OH)D concentrations in postmenopausal women currently receiving antiresorptive or anabolic therapies for the treatment of osteoporosis.
Vitamin D Inadequacy (<30 ng/ml)
Prevalence by Latitude
N = 259 / 532
(48.7%)
N = 342 / 642
(53.3%)
N = 198 / 362
(54.7%)
STUDY DESIGN
Cross-sectional observational study conducted from November 2003 to March 2004
1554 postmenopausal women from 61 sites in North America
Sites evenly distributed across geographic regions by latitude (>42ºN, Boston, MA, between 35-42ºN, and below 35ºN, Memphis,TN)
Informed consent and past medical history obtained
A single blood sample was collected to assess 25(OH)D, calcium, parathyroid hormone (PTH), phosphate, albumin, creatinine (Cr), magnesium, alkaline phosphatase, and total bilirubin concentrations
A 28 item questionnaire was completed by all study subjects
Sites also in Alaska and Hawaii
P = NS for test of trend
STATISTICAL METHODS
Vitamin D Inadequacy (<30 ng/ml):
Age Subgroups
1536 subjects had valid results of serum 25(OH)D
Distribution (mean, standard deviation, median, range, etc.) of serum 25(OH)D was determined, and percent of patients with serum 25(OH)D below various cutpoints was evaluated
Univariate logistic regression models used to assess association between potential risk factors and low 25(OH)D [<30 ng/mL (75 nmol/L)]
Pearson’s correlation coefficient was calculated to assess the relationship between serum 25(OH)D and serum PTH
INCLUSION CRITERIA
Postmenopausal women living in North America, currently on antiresorptive or anabolic therapies to treat or prevent osteoporosis
Subjects were >55 years of age and postmenopausal for a minimum of 2 years
Subjects were required to have taken medication to treat or prevent osteoporosis for a minimum of 3 months, including: alendronate, calcitonin, etidronate, raloxifene, risedronate, or teriparatide
ENDPOINTS
CONCLUSIONS
25(OH)D concentrations were determined using the Nichols Advantage chemiluminescent assay (normal range ng/mL)
Various cutpoints of serum 25(OH)D were used to define vitamin D inadequacy (25(OH)D <9 ng/mL, <15 ng/mL, <20 ng/mL, <25 ng/mL, or <30 ng/mL)
Demographic, dietary, environmental (sun exposure) and health-related variables assessed by subject completed questionnaire
The percent of subjects with biochemical evidence of secondary hyperparathyroidism was determined
SUMMARY
Vitamin D inadequacy is highly prevalent amongst postmenopausal women receiving therapy for osteoporosis.
There was a significantly higher prevalence of vitamin D inadequacy among subjects taking less than 400 IU of vitamin D supplementation daily (63%) compared with those who took at least 400 IU daily (45%) (Figure 2).
206 (16.5%) of subjects had biochemical evidence of secondary hyperparathyroidism.
There was a significant (p<0.001) negative correlation between serum PTH and 25(OH)D; r =-0.3.
Multiple risk factors were associated with Vitamin D inadequacy (p<0.05), including some which are easily modifiable (Table 2).
Up to 52% of North American women currently receiving treatment for osteoporosis have suboptimal 25(OH)D levels.
The prevalence rates of Vitamin D inadequacy are even higher (63%) in those reporting less than 400 IU of Vitamin D supplementation daily.
A high prevalence of Vitamin D inadequacy was seen across all age groups and geographic regions studied.
We advocate the use of Vitamin D supplementation and patient counseling regarding the importance of Vitamin D in all postmenopausal women with osteoporosis.