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Revista Brasileira de Ortopedia

Print version ISSN 0102-3616On-line version ISSN 1982-4378

Rev. bras. ortop. vol.51 no.5 São Paulo Sept./Oct. 2016

http://dx.doi.org/10.1016/j.rboe.2016.08.013 

ORIGINAL ARTICLES

Elderly with proximal hip fracture present significantly lower levels of 25-hydroxyvitamin D

Marcelo Teodoro Ezequiel Guerraa  b  * 

Eduardo Terra Feronb 

Roberto Deves Vianab 

Jonathan Mabonib 

Stéfany Ignêz Pastoreb 

Cyntia Cordeiro de Castrob 

aUniversidade Luterana do Brasil (Ulbra), Departamento de Ortopedia e Traumatologia, Canoas, RS, Brazil

bUniversidade Luterana do Brasil (Ulbra), Hospital Universitário Mãe de Deus, Serviço de Ortopedia e Traumatologia, Canoas, RS, Brazil

ABSTRACT

OBJECTIVE:

To compare serum 25-hydroxyvitamin D (25[OH]D) levels, a serum marker of vitamin D3, between patients with and without proximal hip fracture.

METHODS:

This was a case-control study in which serum samples of 25(OH)D were obtained from 110 proximal hip fracture inpatients and 231 control patients without fractures, all over 60 years of age. Levels of 25(OH)D lower than or equal to 20 ng/mL were considered deficient; from 21 ng/mL to 29 ng/mL, insufficient; and above 30 ng/mL, sufficient. Sex, age, and ethnicity were considered for association with the study groups and 25(OH)D levels.

RESULTS:

Patients with proximal hip fracture had significantly lower serum 25(OH)D levels (21.07 ng/mL) than controls (28.59 ng/mL; p = 0.000). Among patients with proximal hip fracture, 54.5% had deficient 25(OH)D levels, 27.2% had insufficient levels, and only 18.2% had sufficient levels. In the control group, 30.3% of patients had deficient 25(OH)D levels, 30.7% had insufficient levels, and 38.9% had sufficient levels. Female patients had decreased serum 25(OH)D levels both in the fracture group and in the control group (19.50 ng/mL vs. 26.94 ng/mL; p = 0.000) when compared with male patients with and without fracture (25.67 ng/mL vs. 33.74 ng/mL; p = 0.017). Regarding age, there was a significant association between 25(OH)D levels and risk of fracture only for the age groups 71-75 years and above 80 years.

CONCLUSION:

Patients with proximal hip fracture had significantly decreased serum 25(OH)D levels when compared with the control group. Female patients had significantly lower serum 25(OH)D levels in both groups.

Keywords: Vitamin D deficiency; Hip fractures; Osteoporotic fractures

Introduction

Proximal femoral fracture (PFF) has a high incidence in patients older than 65 years and usually results from low-energy trauma. Despite the resources of modern medicine, there is a high mortality rate, around 25-30% yearly.1,2and3 Mortality is mainly due to factors such as advanced age, comorbidities, previous cognitive impairment, and delay in the procedure.1and2 PFF also represents a major cost to public health, mainly due to prolonged hospitalization and related surgical procedures.3and4

Vitamin D plays an important role in calcium metabolism, and consequently in bone mineralization and the osteoporotic picture. Its deficiency is therefore an important risk factor for PFF in the elderly.1,5and6 The best serum marker of this vitamin is 25-hydroxyvitamin D (25(OH)D), whose metabolic product is vitamin D3; values equal to or above 30 ng/mL are considered sufficient.7 The use of vitamin D3 has been recommended to prevent fractures in elderly patients with osteoporosis. However, it is not always routinely used in public healthcare.8, 9-10

This study aimed to compare serum 25(OH)D levels among elderly patients with and without PFF, and to analyze the association of variables such as gender, age, and ethnicity with this condition.

Material and methods

This was a case-control study conducted in the Department of Orthopedics and Traumatology of this institution between January 2013 and May 2015. The study was approved by the Ethics Committee of the institution under CAAE No. 33760914.8.0000.5349.

The fracture group comprised patients over 60 years with PFF. The study included patients with femoral neck, subtrochanteric, and transtrochanteric fractures who had experienced a low-energy fall. The control group included age-matched individuals without PFF history, recruited among the patients attended to at the orthopedics clinic and other medical specialties at this hospital, as well as inpatients admitted for non-orthopedic/traumatological reasons. The exclusion criteria comprised patients outside the age range; with fractures with known history of high energy; with missing data on medical records, such as ethnicity and sex; or with unknown serum levels or without results provided by the laboratory.

Serum 25(OH)D samples were collected for all patients. In the fracture group, blood samples were collected immediately after the patient's admission, before the final surgical procedure. In the control group, samples were collected after outpatient care. Serum levels were measured in a standard laboratory for all samples, measured as nanograms per milliliter (ng/mL).

The results of the blood collection of 25(OH)D were divided in accordance with the Horlick classification, where values below 20 ng/mL are considered deficient; between 21 and 29 ng/mL, insufficient; and above 30 ng/mL, normal.7 The variables gender, age, and ethnicity were considered for purposes of association with the study groups and levels of 25(OH)D.

In order to reject the null hypothesis that serum 25(OH)D would be equal in the case and control groups, the minimum sample size calculated to obtain statistically significant results was 60 patients with PFF (fracture group) and 120 patients without PFF (control group).

Statistical analysis

The statistical program used was SPSS, version 13.0. Results were considered significant at a level of 5% (p ≤ 0.05). Data were expressed as mean and standard deviation or percentage (%). The statistical difference between the fracture and control groups and their respective variables was calculated with the chi-squared and Fisher's exact tests. The Kolmogorov-Smirnov test of normality indicated that the study variables did not present normal distribution; therefore, a nonparametric test was used in the analysis. The Mann-Whitney test was used to compare the mean serum levels of 25(OH)D between groups, and these values were stratified by age and gender. For the ethnicity variable, it was not possible to perform statistical tests due to the insufficient number of cases for the mixed and black ethnicities.

Results

The present sample comprised 341 patients. The fracture group included 110 patients, of whom 82 (74.5%) were female, and the control group consisted of 231 patients, of whom 175 (75.8%) were female. Mean age of the fracture patients was 78.76 ± 9.52 years, and mean age of the controls was 77.31 ± 7.85 years. There was no difference between groups regarding sex or age (p > 0.05). Sample characteristics are described in Table 1.

Table 1 Sample characterization. 

Variable Group p
Control (n = 231) Fracture (n = 110) Total (n = 341)
n % n % n %
Ethnicity
White 218 94.4 106 96.4 324 95.0 0.839a
Black 9 3.9 3 2.7 12 3.5
Mixed 4 1.7 1 0.9 5 1.5

Sex
Female 175 75.8 82 74.5 257 75.4 0.808b
Male 56 24.2 28 25.5 84 24.6

Age (years)
60–65 24 10.4 12 10.9 36 10.6 0.850b
66–70 16 6.9 8 7.3 24 7.0
71–75 50 21.6 21 19.1 71 20.8
76–80 51 22.1 20 18.2 71 20.8
>80 90 39.0 49 44.5 139 40.8

aChi-squared test.

bFisher's exact test.

Source: Authors

The serum levels of 25(OH)D in the control group (28.59 ± 12.31 ng/mL) were significantly higher than in the fracture group (21.07 ± 10.28 ng/mL) (p = 0.000). In the fracture group, considering the Horlick classification, 54.5% (n = 60) patients had deficient serum 25(OH)D levels, and only 18.2% (n = 20) had sufficient values. Among the controls, 38.9% (n = 90) were considered to have sufficient serum levels; 30.3% had deficient serum levels (n = 70) (Table 2).

Table 2 Serum levels of 25(OH)D in the fracture and control groups according to the Horlick classification. 

class
25(OH)D Control Fracture Total
n % n % n %
Deficient 70 30.3 60 54.5 130 38.1
Insufficient 71 30.7 30 27.2 101 29.6
Sufficient 90 38.9 20 18.2 110 32.2
Total 231 100.0 110 100.0 341 100.0

25 (OH) D, 25-hydroxyvitamin D.

Source: Authors

There were no significant differences between the groups regarding the serum levels of 25(OH)D for the age ranges of 60-65 years (p = 0.327), 66-70 (p = 0.417), and 76-80 (p = 0.095). However, significant differences were observed in the age groups 71-75 years (p = 0.003) and over 80 (p = 0.003) (Table 3).

Table 3 Comparison of serum 25(OH)D between the fracture and control groups according to age group. 

class
Age Group n Mean SD pa
60–65 years Control 24 31.5 11.52 0.327
Fracture 12 24.1 14.38
66–70 years Control 16 32.22 10.58 0.417
Fracture 8 29.19 11.79
71–75 years Control 50 28.43 11.37 0.3
Fracture 21 20.50 8.33
76–80 years Control 51 30.82 9.96 0.95
Fracture 20 25.83 9.61
>80 years Control 90 26.11 14.8 0.3
Fracture 49 17.34 8.37

SD, standard deviation.

ap = 0.01.

Source: Authors

For the ethnicity variable, statistical analysis was not possible due to insufficient number of cases for the mixed and black ethnicities. Descriptive data for this variable are shown in Table 4.

Table 4 Comparison of serum levels of 25(OH)D between the fracture and control groups according to ethnicity. 

class
Ethnicity Control Fracture
n Mean SD n Mean SD
White 218 28.73 12.30 106 20.76 10.10
Mixed 9 23.38 10.77 3 29.59 16.32
Black 4 32.83 16.24 1 28.50 0.0

SD, standard deviation.

Source: Authors

Regarding gender, a significant difference was observed in the levels of 25(OH)D between the groups. Lower serum 25(OH)D levels were observed in female patients, with a mean of 19.50 ± 10.01 ng/mL in the fracture group and 26.94 ± 11.23 ng/mL in the control group (p = 0.000). Among males, the mean was significantly higher in the control group (33.74 ± 14.08 ng/mL) when compared with the fracture group (25.67 ± 9.85 ng/mL, p = 0.017).

Discussion

This study showed that patients with PFF had significantly lower serum 25(OH)D levels than the control group. Values considered insufficient in the Horlick classification were observed in both the control group (28.59 ng/mL) and in the fracture group (21.07 ng/mL). Considering this classification, half of patients with PFF had deficient levels of this vitamin. Low levels of 25(OH)D were also found in the control sample, with 30.7% of patients with insufficient levels and 30.3% deficient.

In a meta-analysis that included 15 case-control studies among patients with and without PFF, of the 17 patients analyzed, the serum levels of 25(OH)D in patients with fracture were significantly lower than in the control group.11 Ramason et al.12 conducted a study with 485 elderly with PFF and also found low levels of 25(OH)D in these patients, with a mean value of 19.1 ng/mL, 57.5% deficient, 34.5% insufficient, and only 8% had sufficient levels. Browne et al.,13 using a different serum measuring unit (nmol/L) in a study in Ireland with 156 elderly patients with PFF, found that over 67% of their sample had insufficient or deficient 25(OH)D serum levels. Gumiero et al.,14 in a Brazilian study on gait in patients with PFF, also observed low levels of 25(OH)D, with a mean value of 27.8 ng/mL; 33.7% of the sample had deficient values, which differs from the findings of the present study.7and14 Reduced serum levels of 25(OH)D were significantly related to PFF both in the present study and in previous studies; however, specific differences in serum levels of this vitamin are recognized by various authors, due to its relation to sun exposure and the genetic characteristics of the local population.11,12and13

Considering patients without PFF, Saraiva et al.15 also found the presence of hypovitaminosis in a study in an elderly population, having subdivided the sample into two groups. In the first group, consisting of hospitalized patients, 80% had 25(OH)D deficiency or insufficiency. In the second group, consisting of outpatients, lower values - albeit still significant - were observed: around 55% insufficiency or deficiency in serum levels, which are similar to those found in the control group of the present study.

Females had significantly lower levels of 25(OH)D in both groups of the present study, demonstrating the predominance of this hypovitaminosis in women, a feature recognized by many authors. In a review study, Patton et al. reported that 25(OH)D levels were comparatively lower in women, regardless of the cut-off criteria used.6,13,14,15,16,17and18 Labronici et al.,18 when assessing post-menopausal women, found that 82% of the patients had 25(OH)D levels considered insufficient. Several studies have reported a gradual decline of this vitamin's levels after menopause, which is more significant in older patients. Cauley et al.,19 in a study of over 90,000 post-menopausal women, observed a prevalence of low levels of 25(OH)D among these patients, as well as the subsequent increase in the risk associated with PFF, suggesting serum control in post-menopausal patients as method to investigate this risk. 16,17,19,20and21

Despite the predominance in females, males from the fracture group also presented serum levels considered insufficient (25.67 ng/mL) in the present study. In a prospective study of 1,608 elderly males, Cauley et al.22 demonstrated a significant increase in the risk of hip fractures in patients with low levels of 25(OH)D. The risk of fracture was significant only in male patients with deficient serum levels, which was associated with both PFF23 and bone mineral density of the proximal femur.24

In the present study, the association between vitamin D deficiency and the age variable was significant only in patients aged between 71 and 75 years (p = 0.003) and over 80 (p = 0.003). Ensrud et al.,24 considering only the male population, found a significant association between bone loss and low levels of 25(OH)D among those aged over 75 years. Some authors consider that 25(OH)D levels could present an uneven distribution, characterized by a stable pattern after a certain age. 17,18and19 In the present study, a division according to age of the patients was made in order to discriminate the risk in certain age groups. However, no other studies with this methodology were retrieved, hindering a proper comparison. The variable ethnicity presented an insufficient sample, a limitation also found by many authors in their analysis 19and25 Nevertheless, some authors consider that greater skin pigmentation due to genetic factors may be related to lower serum levels of vitamin D. 12,19and25

Chapuy et al.,8 in a classic clinical trial conducted in England, reported that the use of vitamin D3 associated with calcium led to a significant reduction in risk of fractures in elderly women that did not involve the spine when compared with a control group. Therefore, the prophylactic use of this vitamin is recognized by many authors as an important factor in preventing fractures, especially PFF.1,2,3and4

The main strength of the present sample was its considerable size of 341 patients. In the meta-analysis performed by Lai et al.,11 of the 15 case-control studies with values of 25(OH)D considered significant in elderly PFF, only three showed a total sample higher than that of the present study. Even with a good sample, one bias of the present study was the non-seasonal characterization of the collection year, since sun exposure is known to be associated with levels of 25(OH)D, being relevant even in relation to the inadequate intake of this vitamin.11 The time of serum collection of 25(OH)D, which was made at admission by transfer from another institution and showed variations, may also be considered a limitation of the present study. Furthermore, the study did not consider the clinical and metabolic situations presented by the patient who underwent the exam, such as changes in kidney or liver function, hormonal changes in thyroid function, and medication use, among others. However, despite representing sources of bias, such situations could constitute confounding factors to the various types of variables to be considered.10and11

Conclusion

Lower levels of vitamin D3 were observed in elderly patients with PFF when compared with control patients without fracture. Significantly lower levels of this vitamin in female patients were observed in both groups. There was a significant association between the risk of this hypovitaminosis with PFF in the age ranges between 71 and 75 years and above 80 years. These findings demonstrate the important role of vitamin D3 in the outcome of PFF; its widespread use is suggested as a way to prevent this condition.

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Study conducted at the Universidade Luterana do Brasil (Ulbra), Hospital Universitário, Departamento de Ortopedia e Traumatologia, Canoas, RS, Brazil.

Received: January 14, 2016; Accepted: February 15, 2016

* Corresponding author. E-mail: mguerraz@hotmail.com(M.T. Guerra).

Conflicts of interest

The authors declare no conflicts of interest.

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