Objective:
This study was conducted to access the status of bone mass in females and to look for its correlation with age and vitamin D levels.
Material and Method:
This cross-sectional study was conducted at Islamabad Diagnostic Centre, Islamabad from January to April 2014. A total of 143 females with some history of pains and aches; referred for Dexa scan study and vitamin D levels were included in the study. Bone mineral density was done with Fan beam body DEXA scanner discovery from Hologic (USA) and vitamin D levels were performed on Arcitect I 1000. Results were entered on SPSS version 17. Range and mean were calculated for vitamin D level and frequencies were calculated for dexa scan results. Correlation of dexa scan with age and vitamin D level was calculated using Pearson correlation.
Results:
Total number of females included in the study was 143. Their age range was 17-82 with mean age of 52.36 + 1.137 SD and their vitamin D levels were between 1.28-83.00 with mean level of 13.42 + 0.994 SD. Results of bone mineral density showed that 50 of these had osteoporosis, 49 had osteopenia and 44 had normal bone mineral density. There is a strong negative association of age with bone mineral density with a p value <0.05 and a strong positive association with vitamin D levels with p value <0.05.
Conclusion:
Low BMD has high frequency in our females and has strong association with vitamin D levels. It is recommended that screening be done at an early age and to identify various risk factors for low BMD through large community based studies.
Key words:
BMD (Bone mineral density), DEXA (Dual-energy X-ray absorptiometry), Hypovitaminosis D Osteopenia, Osteoporosis.
Low bone mineral density (BMD) leading to fragile bones, mainly comprises of osteoporosis and osteopenia.
Osteoporosis is a progressive, age related disorder with progressive loss of bone mass and strength resulting in an increased risk of fractures.¹ In osteoporosis, the bone mineral density (BMD) is reduced, bone microarchitecture deteriorates, and the amount and variety of proteins in bone are altered. Osteoporosis is defined by the World Health Organization (WHO) as a bone mineral density of 2.5 standard deviations or more below the mean peak bone mass (average of young, healthy adults) as measured by dual-energy X-ray absorptiometry. Osteopenia is referred to as decrease in bone mineral density which if continues leads to osteoporosis. Prevalence of low BMD manifesting either as osteoporosis or osteopenia, varies according to age, sex, ethnicity and type of skeletal bone.
Osteoporosis may be classified as primary type 1, primary type 2, and secondary. The form of osteoporosis most common in women after menopause is referred to as primary type 1 or postmenopausal osteoporosis, which is attributable to the decrease in estrogen production after menopause. Primary type 2 osteoporosis or senile osteoporosis occurs after the age of 75 and is seen in both females and males at a ratio of 2:1. Secondary osteoporosis may arise at any age and affect men and women equally; this results from chronic predisposing medical problems or disease, or prolonged use of medications such as glucocorticoids (glucocorticoid-induced osteoporosis) or other drugs. Osteoporosis itself has no symptoms; its dangerous aspect is an increased risk of bone fractures. Osteoporotic fractures occur in situations where healthy people would not normally break a bone; they are therefore regarded as fragility fractures. Typical fragility fractures occur in the vertebral column, rib, hip and wrist.
The three main mechanisms by which osteoporosis develop, are inadequate peak bone mass (the skeleton develops insufficient mass and strength during growth), excessive bone resorption, and inadequate formation of new bone during remodelling. Interplay of these three mechanisms underlies the development of fragile bone tissue.² Hormonal factors strongly determine the rate of bone resorption; lack of estrogen (e.g. as a result of menopause) increases bone resorption, as well as decreasing the deposition of new bone that normally takes place in weight-bearing bones.³ In addition to estrogen, calcium metabolism plays a significant role in bone turnover, and deficiency of calcium and vitamin D leads to impaired bone deposition. The parathyroid glands react to low calcium levels by secreting PTH, which increases bone resorption to ensure sufficient calcium in the blood. The role of calcitonin, a hormone generated by the thyroid that increases bone deposition, is less clear and probably not as significant as that of PTH.³
Decreased BMD is a widely prevalent public health problem with substantial morbidity and mortality. Apart from increasing age and hormonal influence other factors such as poor nutrition, inadequate exposure to sunlight and low vitamin D status contribute significantly to severe osteoporosis. Vitamin D plays an important role in skeletal development and maintenance. One of the most important functions of serum 25-OHD is to maintain skeletal calcium balance by promoting calcium absorption in the intestines. It maintains the calcium and phosphate levels needed for bone formation, and also enables the parathyroid hormone to function properly in maintaining serum calcium levels. Chronic vitamin D inadequacy in adults can result in compensatory hyperparathyroidism, leading to increased bone turnover, enhanced bone loss, and increased risk of fragility fracture. Therefore maintaining appropriate levels of serum 25(OH)D and (iPTH) is important for bone health.⁴ Factors that have been reported to be associated with vitamin D inadequacy include skin pigmentation, sunlight exposure, dietary intake, medications, body fat content, and age.⁵⁻⁷ Certain medications have been associated with an increase in osteoporosis risk; steroids and anticonvulsant are classically associated but evidence is arising with other drugs too such as L Thyroxin, heparin, warfarin, proton pump inhibitor and chronic lithium therapy.³
The diagnosis of osteoporosis can be made using conventional radiography and by measuring the BMD.⁸ Conventional radiography is useful, both by itself and in conjunction with CT or MRI, for detecting complications of osteopenia such as fractures; for differential diagnosis of osteopenia. DEXA is considered the gold standard for the diagnosis of osteoporosis and diagnosed when the bone mineral density is less than or equal to 2.5 standard deviations below that of a young (30–40-year-old) healthy adult women reference population and translated as a T-score.⁹ BMD is labeled as normal when T-score > −1.0, osteopenic if T-score < −1.0, osteoporosis when T-score ≤ −2.5 and severe osteoporosis when T-score ≤ −2.5 with fragility fracture. As bone density decreases with age, more people become osteoporotic with increasing age.¹⁰ World Health Organization has established the diagnostic guidelines.¹¹ The U.S. Preventive Services Task Force (USPSTF) recommend that all women 65 years of age or older be screened by bone densitometry.¹² To date, the gold standard technique for diagnosing low BMD is the dual energy x-ray absorptiometry (DXA) which has high predictive validity (sensitivity and specificity). This study was conducted to see the status of BMD in females referred to the centre with some history of aches and pains.
This cross-sectional study was conducted at Islamabad Diagnostic Centre, Islamabad from January 2014 – 30th April 2014. About 143 females with history of bone pains, weakness, lethargy or body aches and pains and referred for vitamin D levels and bone mineral density were included in the study. Women with secondary causes of low BMD, such as hyperthyroidism, hyperparathyroidism or liver disease were excluded from the study.
Bone mineral density was done with Fan beam body DEXA scanner discovery from Hologic (USA). BMD was measured at lumbar spine (L1–L4), hip joint (neck) and forearm (radius and ulna). BMD is reported in terms of T score (T score means comparison of patient BMD with BMD of 30 years old subject of same sex and ethnicity). Bone mineral density is reported as:
Normal if T score is > −1.0
Osteopenia if T score is < −1.0, > −2.5
Osteoporosis if T score is < −2.5
Vitamin D levels were performed on Architect I 1000. Vitamin D level was reported as deficient if it was < 20 IU and insufficient if it was between 20–30. Desirable level is > 30 and levels > 110 are reported as toxic levels.
Results were entered on SPSS version 17. Range and mean were calculated for vitamin D level and frequencies were calculated for DEXA scan results. Correlation of DEXA scan with age and vitamin D level was calculated using Pearson correlation. P value of less than 0.05 was considered as statistically significant.
Total number of females included in the study was 143. Their age range was 17-82 with mean age of 52.36 + 1.137 SD and their vitamin D levels were between 1.28-83.00 with mean level of 13.42 + 0.994 SD. Vitamin D levels in these females are shown in table 1. As shown in the table, out of 143 females only 3.5% had their vitamin D levels in desirable range; it was less than 20 iu 79% cases and between 20-30 iu in 17.6% subjects. Results of bone mineral density showed that 50 of these had osteoporosis, 49 had osteopenia and only 44 had normal bone mineral density. Table 2 shows the bone mineral density in different age groups.
Among these 143 cases 37 are between 17-45 years, and 106 are more than 45 years. As shown in the table, 14 (38%) of females less than 45 years showed osteopenic changes. Whereas Dexa scan findings in subjects > 45 years showed that out of 106 cases (> 45 years), only 23 (22%) had normal bone mineral density, majority (83/78%) of the cases had decreased bone mineral density with 48 (45.3%) cases being diagnosed with osteoporosis and 35 (33%) with osteopenia.
Pearson correlation to look for association of vitamin D levels and age with bone mineral density has shown that among all females, there is a strong negative association of age with bone mineral density with a p value <0.05 and a strong positive association with vitamin D levels with p value <0.05 (Table 3). However in females more than 45 years of age; correlation of Dexa scan with vitamin D was not found much significant (p value 0.379) but it was quite significant with age (p value < 0.05).
| Age group | Normal | Osteopenia | Osteoporosis |
|---|---|---|---|
| < 45 years (n=37) | 21 (57) | 14 (38) | 02 (05) |
| 45–60 years (n=56) | 19 (34) | 22 (39) | 15 (27) |
| > 60 years (n=50) | 04 (08) | 13 (36) | 33 (66) |
Table 2:Vitamin D levels in Females Vitamin D level | Number (%) |
|---|---|
| < 20 | 113 (79) |
| 20-30 | 25 (17.5) |
| > 30 | 05 (3.5) |
Table 3: Association of Bone mineral density with Age and Vitamin D
| BMD and Age | p value | BMD and Vitamin D level | p value | |
|---|---|---|---|---|
| All females (n=143) | –.480 | < .05 | .229 | < .05 |
| Females > 45 years (n=106) | –.385 | < .05 | .086 | .379 |
Osteoporosis is a major public health problem and is a major risk factor for fractures which in turn have strongly effect morbidity and mortality particularly in old age. According to global estimates, about 200 million women suffer from osteoporosis worldwide. The American National Health and Nutrition Examination Survey found that 50% of women over 50 years of age were suffering from low BMD.¹³ Our study showed a strong correlation of bone mineral density with vitamin D levels and in females more than 45 years it is more correlated with age. Pathophysiology of aging in women indicates disconnection of trabecular network leading to reduction in bone mineral, structural deterioration and decrease in bone strength which may explain the increase in prevalence of low BMD by 5% for each ten-year period between 40 and 50 years and 50 to 60 years. Moreover in females the effects on bones are further aggravated by estrogen deficiency due to menopause. The National Health and Nutrition Examination Survey (NHANES) reported an increase after 50 years of age in low BMD with each decade of age,¹³ hence supporting our results. However various other factors; in particular vitamin D levels lead to low bone mineral density at an earlier age so they should be addressed from young age.
Bone health is associated with diet rich in calcium and vitamin D, such as milk, cheese and other dairy products. A study done in Saudia on females of 40 years and above has shown that 59% had low bone mineral density and has been found associated with vitamin D levels, age, education and dietary products. In this study age group of 60–70 years had the lowest bone mineral density.¹⁴ In a study done by Labronici P J et al a strong correlation has been reported between serum vitamin D levels and BMD.¹⁵ Another study reported a significant negative correlation of BMD with body fat and this has been proved in various studies. Moreover they also observed that arthritis had a strong negative correlation with BMD and disease duration.¹⁶ Vitamin D plays a significant role in calcium absorption and thus effect bone content.
A very interesting study was done by Kyoung et al in which men and women older than 50 years were stratified with daily intake of calcium, it was found that low calcium intake was significantly correlated with BMD and increased risk of osteoporosis and vitamin D levels compensate for the negative influences of low calcium intake on bone. They also reported that BMD is also affected by physical activity; however the effect of Vitamin D was greater than physical activity in their study.¹⁷
The main risk associated with osteoporosis is of fractures and osteoporotic fractures are associated with significant morbidity and mortality in the elderly. Fracture risk calculators assess the risk of fracture based upon several criteria, including BMD, age, smoking, alcohol usage, weight, and gender.⁸ The underlying mechanism in all cases of osteoporosis is an imbalance between bone resorption and bone formation and various factors may lead to this imbalance. A study done on Vitamin D Levels, Physical and Biochemical Characteristics of Patients with Osteoporotic Hip Fractures showed that 50% of patients with fractures had vitamin D levels <20ng/ml.¹⁸
Fractures occurring during adulthood on exposure to some exercise, weight lifting or falls indicate weak bones and low bone mass density and are a concern for future risk of osteoporosis. One of the studies done on children showed that vitamin D status was a key determinant of BMD. They also observed a significant difference in parathyroid (PTH) levels according to vitamin D levels and calcium intake did not affect the association between serum vitamin D level and PTH. They also reported that physical activity also enhances BMD.¹⁹ Hence fractures and low bone density follow a viscous cycle; one leading to other and aggravating the condition further.
Early screening of all such cases should be made mandatory as managing fractures in elderly is tedious and requiring meticulous and sometimes prolonged support from family as well as health personal. In addition, the mortality, morbidity, disability and financial cost associated with management of fractures make screening for low BMD imperative. Prevention of osteoporosis by change of lifestyle and dietary modification are the most important potentially modifiable risk factors. Smoking cessation and moderation of alcohol intake are commonly recommended as ways to help prevent it. Weight-bearing endurance exercise and/or exercises to strengthen muscles improve bone strength in those with osteoporosis. Aerobics, weight bearing, and resistance exercises all maintain or increase BMD in postmenopausal women.
Studies of the benefits of supplementation with calcium and vitamin D are conflicting, possibly because most studies did not have patients with low dietary intakes. Some meta-analyses have found a benefit of vitamin D supplements combined with calcium for fractures, they did not find a benefit of vitamin D supplements alone.²⁰ Bisphosphonates are useful in decreasing the risk of future fractures in those who have already sustained a fracture due to osteoporosis. Teriparatide (a recombinant parathyroid hormone) has been shown to be effective in treatment of women with postmenopausal osteoporosis. Hormone replacement therapy, while effective for osteoporosis, is only recommended in women who also have menopausal symptoms. Certain drugs like alendronate, etidronate, risedronate, raloxifene and strontium ranelate can be helpful for the prevention of osteoporotic fragility fractures in postmenopausal women with osteoporosis.
In conclusion, low BMD has high frequency in our females and has strong association with vitamin D levels. As vitamin D deficiency is prevalent in our society; significant efforts should be made by highlighting its role and national recommendations for vitamin D intake should be stressed. Moreover, it is recommended that screening be done at an early age and to identify various risk factors for low BMD through large community-based studies. Conflict of Interest: This study has no conflict of interest to declare by any author.
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