Prevalence of vitamin D inadequacy in patients attending a metabolic bone clinic in Medway

ABSTRACT

Background: It is well established that vitamin D levels are sub-optimal in the elderly and that adults with fragility fracture have low levels of serum vitamin D.

Objectives:?To investigate the prevalence of vitamin D inadequacy in Medway, Kent in patients attending a metabolic bone clinic and in patients with fragility fractures and to compare levels with data previously presented from Glasgow.

Research design and methods:?Retrospective patient records audit of patients attending the metabolic bone clinic from 1998 to 2005.

Results:?There were data for 870 patients, 77.5% of the patients were women (n = 674) and 48.2% (n = 420) of patients had a fragility fracture. The mean age was 61.6 years (SD = 14.12), 56.4% were aged 60 years or over and 17.7% were aged 75 years or over. The mean vitamin D level was 47.7?nmol/L (19.1?ng/mL), SD = 25.8 (10.3). Of the patients 88.7% had a vitamin D level < 80?nmol/L, 81.4% < 70?nmol/L and 59.1% < 50?nmol/L.

Of the 420 patients with fragility fracture, 78.1% were women and the mean age was 66.6 years (SD = 12.22). The mean vitamin D level was 45.3?nmol/L (18.1?ng/mL), SD = 25.8 (10.3). In patients not receiving supplementation (n = 222) the mean vitamin D level was 40.5?nmol/L (16.2?ng/mL), SD = 20.9 (8.4) and 95.9% of patients had a vitamin D level < 80?nmol/L, 89.6% < 70?nmol/L and 71.2% < 50?nmol/L.

In order to compare data from Medway with previously published data from Glasgow, a subset of 198 patients with fragility fracture, aged over 50 years, attending the metabolic bone clinic and not receiving supplementation with calcium and/or vitamin D was analysed. There were 76.6% women and the mean age was 68.6 years (SD = 9.1). The mean vitamin D level was 40.0?nmol/L (16.0?ng/mL), SD = 21.5 (8.6). Of these patients 96.4% had a vitamin D level < 80?nmol/L,89.7% < 70?nmol/L and 73.2% < 50?nmol/L.

Data on the month of vitamin D assessment were available for 499 patients. The mean vitamin D in the summer (April–September) months (n = 217) was significantly higher than in the winter (October–March) months (n = 281): 53.2?nmol/L (SD = 29.4) versus 47.3 (SD = 24.9), p = 0.02.

Parathyroid hormone (PTH) levels were available for 289 patients. Mean vitamin D levels in the 47 patients with PTH levels above the reference range were significantly lower than vitamin D levels in the 238 patients within the reference range for PTH: mean 31.1?nmol/L, SD = 21.1 versus mean 46.5?nmol/L, SD = 24.8 (?p = 0.000092). Four patients had PTH levels below the reference range.

Conclusions:?The prevalence of vitamin D inadequacy is high in patients attending a metabolic bone clinic, in particular in those patients with fragility fractures. The prevalence of inadequacy is comparable with that seen in Glasgow.