Does routine blood bone biochemistry predict vitamin D insufficiency in elderly patients with low-velocity fractures?

An overview of the prevalence of 25-hydroxy-vitamin D inadequacy amongst elderly patients with or without fragility fracture in the United Kingdom

BACKGROUND

Many studies have investigated the prevalence of 25-hydroxy-vitamin D inadequacy throughout the world and found a high prevalence of 25-hydroxy-vitamin D inadequacy in older patients, particularly those with fragility fracture.

SCOPE

To review the findings from vitamin D audits from six units across the UK and compare with previously published data from around the world. Results from four units have been previously published (Belfast, Glasgow, London and Medway) and this paper presents new data from Southampton and Carshalton, and further sub-analysis of the data from Medway.

FINDINGS

Three audits of patients attending metabolic bone clinics (Carshalton, Medway and Southampton) identified 954 patients, of which overall 49% had a prior fragility fracture. Mean 25-hydroxy-vitamin D levels ranged from 47.7 nmol/L to 62.4 nmol/L. Of these patients 72.9-88.9% had a 25-hydroxy-vitamin D level < 80 nmol/L, 68.8-83.3% < 70 nmol/L and 37.5-59.1% < 50 nmol/L. The mean age of patients ranged from 60.0 to 67.5 years. Sub-analysis of the data by fracture status revealed that patients with fracture had lower mean levels of 25-hydroxy-vitamin D compared with patients without fracture. This was statistically significant in the sub-analysis of the Medway data (45.3 nmol/L versus 49.9 nmol/L, p < 0.005). Three audits identified 330 patients with fragility fracture. Audits from Glasgow and Belfast specifically identified patients with fragility fracture. A subgroup of patients with fracture aged over 50 years from the Medway audit was also included in this group. Mean levels of 25-hydroxy-vitamin D ranged from 40.0 nmol/L to 52.3 nmol/L. 83.7-96.4% of patients had a 25-hydroxy-vitamin D level < 80 nmol/L, 73.3-89.7% < 70 nmol/L and 55.8-73.2% < 50 nmol/L. The mean age of patients ranged from 65.3 to 68.6 years. The audits carried out in Belfast and Medway were also divided by supplementation status. Mean 25-hydroxy-vitamin D levels were 48.1 nmol/L in Belfast and 40.5 nmol/L in Medway in the patients not receiving supplements and 53.8 nmol/L and 59.9 nmol/L, respectively in the patients receiving supplements. The difference was statistically significant in the Medway audit (p < 0.0001), but not in the smaller Belfast audit (p = 0.216). As would be expected, the prevalence of 25-hydroxy-vitamin D inadequacy was higher in the patients not receiving supplements, for example at the 70 nmol/L threshold: 82.6% versus 67.1% in Belfast and 89.6% versus 72.7% in Medway. Three audits specifically identified 694 patients with hip fracture (Belfast, Glasgow and London). Mean levels of 25-hydroxy-vitamin D ranged from 24.7 nmol/L to 36.1 nmol/L. Of these patients 90.7-99.0% had a 25-hydroxy-vitamin D level < 80 nmol/L, 88.4-98.0% < 70 nmol/L and 81.6-92.7% < 50 nmol/L. The mean age of patients ranged from 73.4 to 80.5 years.

CONCLUSION

Inadequate 25-hydroxy-vitamin D levels are extremely common in the elderly and particularly so in patients with fragility fracture - specifically in those with hip fracture. Although the differing audit specifications and assay techniques used make direct comparisons difficult, the data do provide a snapshot of 25-hydroxy-vitamin D status across the UK and are consistent with those previously observed elsewhere in Europe and the rest of the world.

Prevalence of vitamin D inadequacy in Scottish adults with non-vertebral fragility fractures

BACKGROUND

It is well established that vitamin D levels are sub-optimal in the elderly and that adults with fragility fracture are more likely to have serum vitamin D levels either lower than those of control patients of similar age, or below the normal range.

OBJECTIVES

To investigate the prevalence of vitamin D inadequacy in an elderly population presenting to the South Glasgow Fracture Liaison Service with non-vertebral fragility fractures in order to assess the extent of the problem.

RESEARCH DESIGN AND METHODS

The retrospective arm of this study used data from an established database to identify patients aged over 50 years admitted to South Glasgow University Hospitals over the previous 4 years with hip fracture. The prospective arm identified the first 50 patients aged over 50 presenting with a clinical non-vertebral fragility fracture with osteoporosis as measured by axial spine and/or hip DEXA (T-score < -2.5) after November 2004.

RESULTS

In the retrospective arm, 626 patients were identified from the database: mean age 80.5 years; 94% were aged over 60 and 74% were aged over 75. Data analysis was limited to 548 patients aged over 60 years with vitamin D recordings and not receiving supplementation with calcium and vitamin D. The mean vitamin D level was 24.7 nmol/L (9.9 ng/ml) SD = 17, however, it is likely that the true mean is lower since in approximately 25% of cases vitamin D levels were reported as < 15 nmol/L (effectively unrecordable). These were transcribed as 15 nmol/L in order to permit a numerical value to be calculated. In the absence of an agreement on what should constitute a diagnostic serum level of vitamin D inadequacy, a number of thresholds were considered--97.8% had vitamin D levels below 70 nmol/L and 91.6% had vitamin D levels below 50 nmol/L. There were no significant differences by patient sex, age or season of presentation. The mean age of patients in the prospective arm was 65.8 years (range 50.6-83.8), 72% were aged over 60 and 16% were aged over 75. The mean vitamin D level was 44.1 nmol/L (18.4 ng/ml) SD = 25.3; 82% had vitamin D levels below 70 nmol/L and 72% had vitamin D levels below 50 nmol/L. Although numbers were too small to justify extensive subgroup analyses, the mean vitamin D level in the 13 patients with hip fracture (34.5 nmol/L) was lower than in the 37 with non-hip fractures (48.2 nmol/L).

CONCLUSIONS

This study confirms almost universal vitamin D inadequacy among 548 elderly patients admitted to hospital with hip fracture, regardless of whether a threshold of 50 nmol/L or 70 nmol/L was used. However, among a prospective subset of 50 patients with clinical fragility fractures, especially those with non-hip fractures, the prevalence of inadequacy was substantially lower. It may be that vitamin D represents a correctable risk factor for fragility fracture in the elderly, possibly specifically for the hip.