Bone mineral density and its correlation with Vitamin D status in healthy adults of Manipur – A cross-sectional study

However, with increasing avoidance of sun exposure by the general population, they should ensure adequate dietary intake of vitamin D. The primary dietary sources of vitamin D are fortified dairy products, other dietary sources include egg yolks, fish oils and enriched cereal products. Vitamin D provided by the plant source is in the form of vitamin D2, whereas that provided by the animal source is in the form of vitamin D3, however quantities obtained from these sources are thought to be insufficient in achieving optimal serum vitamin D concentrations. [2]


Introduction
Ultraviolet radiation from the sun is the chief source of vitamin D in human, skin synthesis is limited by numerous factors, including pigmentation, time of day, the season of the year, latitude, age, and percentage of the skin surface area available for exposure. [1] However, with increasing avoidance of sun exposure by the general population, they should ensure adequate dietary intake of vitamin D. The primary dietary sources of vitamin D are fortified dairy products, other dietary sources include egg yolks, fish oils and enriched cereal products. Vitamin D provided by the plant source is in the form of vitamin D2, whereas that provided by the animal source is in the form of vitamin D3, however quantities obtained from these sources are thought to be insufficient in achieving optimal serum vitamin D concentrations. [2] Osteoporosis, the skeletal disease of bone thinning and compromised bone strength, characterized by bone fragility and increased susceptibility to fractures, especially of the spine and hip.5 Since bone loss occurs without symptoms, osteoporosis is a 'silent disease.' Osteoporosis in men is a major underestimated public Patients with chronic disorders were excluded from the study.

Methdology:
The serum 25-OH vitamin D level was estimated by using an enzyme immunoassay (EIA) kit (IDS immune diagnostic systems, United Kingdom). normal if it was ≥30 ng/mL (≥75 nmol/L), insufficient if it was between 20 and 30 ng/mL (50 and 75 nmol/L), and deficient if it was <20 ng/mL (<50 nmol/L) The BMD of the lumbar spine was determined using enCORE -based X-ray bone densitometer (Lunar Prodigy advance, GE Medical Systems, USA), which is based on the DEXA scan. AP spine measurement and analysis provides an estimation of BMD for the lumbar spine. Based on WHO classification for diagnosis of osteoporosis using BMD measurements, each group was classified into three types: normal if T-score is -1 SD and above, osteopenia if T-score is in between -1.0 SD and -2.5 SD, and osteoporosis if T-score is -2.5 SD and below.
Statistical Analysis: After collection, data were checked for consistency and competency and completeness. Then the data was entered in database Statistical Package for the Social Sciences (SPSS) software version 21. Statistical analysis of the data was done using descriptive statistics, mean and standard deviation were obtained. Pie chart diagram was used to show the status of Vitamin D and bone mineral density among both the age groups. Scattered plot graph was also used to plot the relationship between the variables. P-value < 0.05 was taken as significant.

Results
The study was conducted among 100 subjects and they were divided into two groups (18-35yrs) and ≥50yrs depending on their age with 50 subjects in each group.   Table 2 shows the levels of BMD among the subjects with 25 (OH) D insufficiency. It was found that 13 (86.7%) and 1 (6.7%) subjects were osteopenic and osteoporotic, respectively, in the younger age group (18-35 years). But, all the men in the older age group (≥50 years) were having low bone mass where 10 (45.5%) and 12 (54.5%) subjects were having osteopenia and osteoporosis, respectively. Table 3 shows that none of the men in both groups (20-35 years or ≥50 years) had normal BMD. The majority of the subjects had BMD readings consistent with osteoporosis that is 2 (66.7%) and 8(100%) subjects in age groups of 18-35 years and ≥ 50 years, respectively. Table 4 shows the status of vitamin D levels among the age group 18-35 years and ≥50 years.

Table 3: Classification of subjects with deficiency 25 (OH) D based on T-score
Among the younger age group of 18-35 years, 15 (30%) were having an insufficient level, and only 3 (6%) were deficient whereas in the older age group of ≥ 50 yrs, 22 (44%) subjects had insufficient levels, and 8(16%) subjects were having deficient levels. Table 5 shows the BMD status according to WHO T-score classification in the age group 18-35years and ≥50 years.
Karthika et al.  Bone mineral density and its correlation with Vitamin D status in healthy adults.   Fig. 3 shows the correlation between vitamin D and BMD among all the subjects as a group, which was also positively correlated with the values of correlation coefficient and R2 Linear were 0.655 and 0.429, respectively.

Discussion
The present study revealed that the majority of subjects with insufficiency of 25(OH)D had low bone mass, whereas all the subjects with 25(OH)D deficiency had BMD readings consistent with osteopenia or osteoporosis in both the age groups. This study also showed a positive correlation between BMD and 25(OH)D in most subjects, particularly in the groups with insufficiency or deficiency of 25 ( The present research demonstrated a significant strong positive correlation between 25(OH)D levels and BMD values at the studied site among both the age groups. However, no such association has been found in other studies. 8,9,10 This can be partially explained by differences in population, age group, and the difference in the sites of the body studied due to different composition of trabecular and cortical bone tissue. For example, Garnero et al. 11 and Allaliet al.12 failed to show any significant correlation between 25(OH)D levels and BMD after adjusting for age. However, Rassouliet al13 found a positive correlation with spine BMD, but not with hip BMD.
Osteoporosis in men occurs from a complex interplay of different factors, including age-related sex hormone deficiency, genetics, and lifestyle choices (e.g., physical inactivity, tobacco and excessive alcohol use), as well as specific risk factors (e.g., corticosteroid excess) that cause bone loss and microarchitectural disruption. On the basis of our findings, we emphasize that it is important to measure 25(OH)D levels in patients with low bone mass, rather than relying on BMD alone.
Limitation of the study: One limitation of the study is that only a single measurement of vitamin D was done and apart from the analysis of bone mineral density from the lumbar spine by DEXA scan no other bone markers were measured. Also, other factors such as duration of exposure to sunlight, sex hormone level, level of physical activity and lifestyle were not studied.

Conclusion
The study revealed that there was a higher prevalence of hypovitaminosis D status among older men compared to the younger age group in Manipur. This study also showed a positive correlation between vitamin D levels and bone mineral density in healthy adults and that there is a decreased risk for osteoporosis in ageing men with optimal 25(OH)D.