Body Mass Index (BMI) is a good indicator for measurements of Bone Mineral Density (BMD) which measures the density of minerals present in the bones using a special scan. This study was conducted to assess the association between BMI and status of BMD among 101 individuals who underwent Dual-Energy X-ray Absorptiometry (DEXA) scan. 39 subjects had normal and 62 had low bone mineral density. BMD was low in 82.4% of people with normal BMI, 78.1% among overweight, and 44.2% among obese. There was a statistically significant association between these two variables (
Bone mineral density (BMD) test measures the density of minerals present in the bones using a special scan. This can be used to assess the strength of bones. Bones naturally become thinner as you grow older because existing bone is broken down faster than the new bone made. As a result of this, calcium and other minerals decrease in the bones and they become light in weight, less dense, and more fragile. The bones might break if it goes thinner and weaker. Therefore, thicker bones take longer time to get osteoporosis. Although osteoporosis can occur in men, it is most common in women older than 65 years of age. Prospective studies by Ravn et al. [
The present study was conducted to assess the association between BMI and status of BMD among individuals referred to Department of Radio diagnosis for DEXA scan.
The present retrospective study was conducted in Gulf Medical University, Ajman, UAE. For the study, people who were referred to the Department of Radio diagnosis for DEXA scan were selected. People who underwent DEXA scan from January till September 2009 formed the study subjects. Those patients referred for DEXA scan had metabolic syndromes, bone diseases, and few had difficulty in walking. As it is a case record analysis “agree to participate” does not arise. DEXA Scanning was performed by two technicians, and the interpretation was done by one radiologist. For the present study, 25- to 80-year old individuals of both genders who attended various departments of Gulf Medical College Hospital and Research Centre, Ajman, and whose densitometries recovered were included. The tool used for data collection consisted of sociodemographic details like age and gender. Height and weight were measured and respondents were dressed in light clothes and did not wear shoes. BMI was calculated from the height and weight recorded while performing DEXA scan. The BMI was calculated based on the formula weight (kg)/[height (m)]2. The standard categorisation of BMI by CDC [
Dual-Energy X-ray Absorptiometry (DEXA) is the most accurate way to measure BMD. A certified technician measured BMD at the femoral neck and the lumbar spine (L2 to L4) using a DEXA densitometer. WHO criteria were used for categorizing the respondents based on DEXA results. The statistical analysis included descriptive statistics to rule out the association between sociodemographic characteristics and DEXA scan result, BMI, and status of BMD. The statistical tests used in this study were chi-square test and logistic regression. The variables considered were gender, age, and BMI. The difference between the subjects was considered significant if the
The study population consisted of 101 individuals. Distribution of gender showed that 87.1% were females and the remaining were males. The sex ratio was found to be male : female = 1 : 6.7. Age ranged from 25 to 80 years. The mean and standard deviation of age was
Distribution of respondents according to age, gender, and BMI.
Variable | Group | No. | % |
---|---|---|---|
Gender | Male | 13 | 12.9 |
Female | 88 | 87.1 | |
Age | 25–39 | 15 | 14.9 |
40–59 | 69 | 68.3 | |
60 and above | 17 | 16.8 | |
BMI | Normal | 17 | 16.8 |
Overweight | 32 | 31.7 | |
Obese | 52 | 51.5 |
The results of the DEXA scan of 101 respondents show that 35.6% were osteopaenic and 25.7% had osteoporosis. 38.6% had normal DEXA scan results. Among patients with osteopaenia and osteoporosis, about 77.4% were overweight or obese. In the present study, none of the participants in the age group 25–39 years had osteoporosis. Maximum number of osteoporosis cases was seen in the age group of 60 years and above. In the age group of 40–59 years, only 23% had osteoporosis. The details of DEXA scan results are given in Table
Distribution of bone mineral density according to independent factors.
Status of bone mineral density | ||||||||
Independent factors | Normal | Osteopaenic | Osteoporosis | Total | ||||
No. | % | No. | % | No. | % | |||
BMI | Normal | 3 | 17.6 | 7 | 41.2 | 7 | 41.2 | 17 |
Overweight | 7 | 21.9 | 12 | 37.5 | 13 | 40.6 | 32 | |
Obese | 29 | 55.8 | 17 | 32.7 | 6 | 11.5 | 52 | |
Age (in Years) | 25–39 | 10 | 66.7 | 5 | 33.3 | — | — | 15 |
40–59 | 27 | 39.1 | 26 | 37.7 | 16 | 23.2 | 69 | |
60+ | 2 | 11.8 | 5 | 29.4 | 10 | 58.8 | 17 | |
Total | 39 | 38.6 | 36 | 35.6 | 26 | 25.7 | 101 |
For further analysis, the whole group based on the DEXA scan result was divided as normal and low bone mineral density. There were 39 subjects with normal BMD and 62 with low BMD. BMD was low in 82.4% of people with normal BMI, 78.1% among overweight and 44.2% among obese. The association between BMI and BMD was found to be statistically significant (
Association between bone mineral density and independent factors.
Status of bone mineral density | |||||||
Independent factors | Normal | Low BMD | Total | ||||
No. | % | No. | % | ||||
BMI | Normal | 3 | 17.6 | 14 | 82.4 | 17 | |
Overweight | 7 | 21.9 | 25 | 78.1 | 32 | ||
Obese | 29 | 55.8 | 23 | 44.2 | 52 | ||
Age (in Years) | 25–39 | 10 | 66.7 | 5 | 33.3 | 15 | |
40–59 | 27 | 39.1 | 42 | 60.9 | 69 | ||
60+ | 2 | 11.8 | 15 | 88.2 | 17 | ||
Total | 39 | 38.6 | 62 | 61.4 | 101 |
In the present study, age and BMI were the two factors found to be statistically associated with BMD. These two variables were put into a binary logistic regression model to find the crude and adjusted Odds Ratio (OR). The results of this analysis showed that compared to normal BMI, the chances of getting low BMD in overweight persons are 50% less. This association was not statistically significant. But among obese persons, the chance of getting low bone mineral density was 89% less compared to normal, which was statistically significant. As far as age is concerned, compared to those in age group 25–39 years the chance of getting low bone mineral density in persons aged 40–59 years was 4.24 times higher, and this was statistically significant. But those with age 60 years and above, the chance of low bone mineral density is 23 times higher compared to those in the age group 25–39 years. This association was found to be statistically significant. The details are depicted in Table
Crude and adjusted odds ratio of independent variables.
Independent factors | Crude | Adjusted | |||
OR | CI | OR | CI | ||
BMI | Normal | 1 | — | 1 | — |
Overweight | 0.77 | 0.17–3.44 | 0.50 | 0.10–2.55 | |
Obese | 0.17 | 0.04–0.66 | 0.11 | 0.02–0.50 | |
Age (in Years) | 25–39 | 1 | — | 1 | — |
40–59 | 3.11 | 0.95–10.10 | 4.24 | 1.09–16.53 | |
60+ | 15.0 | 2.42–93.0 | 22.94 | 3.12–168.68 |
Osteoporosis is a major public health problem all over the world. The epidemiology of osteoporosis is, however, not well known in most of the Middle East countries. The present study was conducted in Gulf Medical University, Ajman, UAE, to identify the factors associated with the occurrence of low BMD. The three factors considered included age, gender, and BMI. DEXA scan uses two different X-ray beams to assess the bone density in the spine and hip. Although osteoporosis involves the whole body, measurements of BMD at one site can be predictive of fractures at other sites. Less X-ray beams pass through strong bones. DEXA can measure as little as 2% of bone loss per year. It is quick, and very low doses of radiation are used, but it is more costly when compared to ultrasound testing.
The correlation between BMD at the femoral neck and BMI observed was highly positive in a crosssectional study conducted among postmenopausal women by Steinschneider et al. [
The previous literature of Baheiraei et al., [
This study is an attempt to address one of the important public health problems which can be controlled if preventive measures are taken at an early stage. More about the risk factors could not be investigated as this is a retrospective case record analysis.
The results of this study suggest that advancing age and lower BMI are important risk factors for the occurrence of low BMD. Further studies are required to investigate the effect of other factors like exposure to sunlight, calcium intake, and other habits like smoking, diet, and so forth.
The authors are heartily thankful to Mrs. Jancy Joshi, Secretary to the GMU Research Division for computation of data and help in secretarial work in the preparation of this article.