|Year : 2020 | Volume
| Issue : 2 | Page : 135-140
Bone health and its association with vitamin D and other covariates: A community-based study among women in a rural area of West Bengal
Tania Pan1, Aparajita Dasgupta2, Bobby Paul3, Lina Bandyopadhyay4, Amal Titto V. Augustine1, Sweta Suman1
1 Junior Resident, Department of PSM, All India Institute of Hygiene and Public Health, Kolkata, West Bengal, India
2 Director Professor, Department of PSM, All India Institute of Hygiene and Public Health, Kolkata, West Bengal, India
3 Assistant Professor and Head, Department of PSM, All India Institute of Hygiene and Public Health, Kolkata, West Bengal, India
4 Equated Associate Professor and Public Health Specialist Grade I, Department of PSM, All India Institute of Hygiene and Public Health, Kolkata, West Bengal, India
|Date of Submission||26-Mar-2019|
|Date of Decision||08-Jun-2019|
|Date of Acceptance||16-Apr-2020|
|Date of Web Publication||16-Jun-2020|
Department of PSM, All India Institute of Hygiene and Public Health, 110 C R Avenue, Kolkata, West Bengal
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Low bone mineral density (BMD) is implicated in the pathogenesis of osteoporosis and osteopenia, and primarily manifest as fragile bones. This is a rapidly emerging global health problem with increasing prevalence in India. Objectives: The objective of this was to assess the status of bone health and find its determinants among women aged 40 years and above in a rural population of West Bengal. Methods: A community-based cross-sectional study was conducted from May 2017 to April 2018 among 260 women aged 40 years and above residing in the selected villages of Singur through multistage random sampling. Each respondent was interviewed using a structured schedule. Serum Vitamin D and calcium levels were investigated. BMD was assessed through calcaneal quantitative ultrasound. Osteoporosis was diagnosed among those with T-score ≤−2.5, while those with 25(OH) Vitamin D <30 ng/ml were classified to have Vitamin D insufficiency (VDI). Individuals with BMD T-score <−1 were considered to have low BMD. Inferential statistics were employed to find the associates of poor bone health. Results: Out of 260 participants, 34 (13.1%) were screened positive for osteoporosis and 77.7% had low BMD. Approximately 75% had VDI. On multivariable analysis, VDI (adjusted odds ratio [95% confidence interval] = 4.13 [2.12, 8.37]) was a significant predictor of low BMD after adjustment for poor education, decreasing diet score, menopause, presence of comorbidity, underweight, and overweight explaining 43.6% of the variance. Conclusion: Serum Vitamin D levels are implicated to play a crucial role in bone metabolism; however, its effect on the body in accordance with other important hormones should be explored.
Keywords: Calcaneal quantitative ultrasonography, community based, low bone mineral density, osteoporosis, sun index, Vitamin D insufficiency
|How to cite this article:|
Pan T, Dasgupta A, Paul B, Bandyopadhyay L, Augustine AT, Suman S. Bone health and its association with vitamin D and other covariates: A community-based study among women in a rural area of West Bengal. Indian J Public Health 2020;64:135-40
|How to cite this URL:|
Pan T, Dasgupta A, Paul B, Bandyopadhyay L, Augustine AT, Suman S. Bone health and its association with vitamin D and other covariates: A community-based study among women in a rural area of West Bengal. Indian J Public Health [serial online] 2020 [cited 2020 Sep 23];64:135-40. Available from: http://www.ijph.in/text.asp?2020/64/2/135/286809
| Introduction|| |
The importance of healthy bones is immense at every stage of life. For children, strong healthy bones assist in reaching their optimum growth level. Bones reach their peak bone mass in the age group of 20–40 years, which is when our bones are at their strongest. For adults, strong healthy bones mean that they can maintain their bone density and lead a fit and active life well into old age. Poor bone health is characterized by decrease in bone mass and reduction in bone microarchitecture and strength. This decline in bone integrity leads to an increased risk on fragility fractures, pain, and disability.
Low bone mineral density (BMD) is implicated in the pathogenesis of osteoporosis and osteopenia, and primarily manifest as fragile bones. The prevalence of low BMD varies according to age, sex, ethnicity, and type of skeletal bone. There is evidence to suggest that Indians have lower bone density as compared to their North American and European counterparts, and also osteoporotic fractures occur 10–20 years earlier. In the present scenario where noncommunicable diseases are on the rise, this health condition is another rapidly emerging global problem with a high prevalence of poor bone health in the developed countries and an increasing trend in developing countries. Owing to effect of time-bound physiological changes, women are mostly affected. The greatest bone loss occurs in women during perimenopause and is associated with estrogen insufficiency. This slowly progressing metabolic bone disease is widely prevalent in India, where an approximate figure of 30 million women has been diagnosed to suffer from osteoporosis. It is estimated that by 2050, half of the world's fractures will occur in Asia.
Osteoporosis is difficult to treat and is still incurable, and thus, prevention is critically important. Sadly, most are unaware of it till a fracture occurs. Screening of at-risk population is, therefore, essential. Dual-energy X-ray absorptiometry is the gold standard for the measurement of BMD. However, the most commonly used modality of measuring bone density still remains to be calcaneal quantitative ultrasonography (QUS), which is evolving as a promising technique., Being cost-effective and portable with no deleterious effect of ionizing radiation, it can be considered as a robust alternative method to screen for osteoporosis at the community level.
There are few studies regarding bone health status in different parts of India. The very few that were found were not community based., This study was conducted with the objectives to find the status of bone health and its causative and contextual determinants with special emphasis on Vitamin D among women aged 40 years and above in a rural population of West Bengal.
| Materials and Methods|| |
This study was a cross-sectional community-based observational study conducted over a period of 1 year from May 2017 to April 2018. Women aged 40 years and above, residing in the villages under the purview of Rural Health Unit and Training Centre (RHUTC), Singur, were included in the study. Pregnant and lactating women, those who had not given written informed consent, critically ill women, and those who had Vitamin D supplementation within the previous 6 months were excluded from the study. Ethical approval was obtained from the Institutional Ethics Committee of All India Institute of Hygiene and Public Health (AIIHPH; dated November 26, 2016).
Reference of a study done in Mumbai in 2005 among 200 women has been considered for sample size calculation where the prevalence of osteopenia and osteoporosis in women aged more than 40 years was found to be 42%. After taking confidence level of 95%, relative error of 15%, and nonresponse rate of 10%, the final sample size was calculated to be 260.
RHUTC, Singur, is the rural field practice area of AIIHPH, Kolkata, which caters to 64 villages through two union primary health centers (UPHCs). Multistage random sampling was done. In the first stage, three villages were selected randomly from each of the two UPHCs. Sampling frame of women aged 40 years and above was prepared from the voter lists of the selected villages. After calculating the number of participants from each village, a required number of samples as per population proportionate to size were drawn from the sampling frame of each village by simple random sampling. If the selected individual did not meet the selection criteria, who could not be contacted after two visits, simple random sampling without replacement was done to select another study participant.
A predesigned, pretested structured schedule was used to collect data. Face validity and content validity of the instrument were checked by experts of AIIHPH. Data were collected and analyzed on the following domains:
- Sociodemographic characteristics
- Addiction behavior
- Diet score for each participant was computed by adding the days of consumption of milk and dairy products, egg yolk, and fish in the past 7 days
- Physical activity was assessed by the Short Questionnaire to Assess Health-Enhancing Physical Activity (SQUASH) which includes self-reporting physical activity. For each individual, metabolic equivalent task (MET)-minutes per week were derived from Ainsworth's compendium of physical activity. Health-enhancing physical activity was considered for >600 MET-min/week
- Height and weight were measured following standard operating procedures. Individuals with body mass index (BMI) ≥25 kg/m2 were reported as overweight/obese and those <18.5 kg/m2 were underweight
- Morbidity score for each participant was calculated by adding the total number of self-reported chronic morbidities
- Data regarding hours of exposure to sunlight along with body parts exposed were recorded. Barger-Lux-Heaney index was calculated as per formula: Sun index = Sun exposure per week × fraction of body surface area exposed to sunlight
- Serum 25-hydroxy Vitamin D was investigated. Individuals with 25(OH) Vitamin D <30 ng/ml were classified to have Vitamin D insufficiency (VDI)
- Serum total calcium was also investigated. Serum level ranging from 8.9 to 10.1 mg/ml was considered to be normal.
The basis for selection of the independent variables is mostly based on literature review. However, certain variables which were hypothesized to have a role in bone health were invariably included by the researcher.
Dependent variable: Bone health status: Estimation of BMD was done through calcaneal QUS. Osteoporosis was diagnosed among those with T-score ≤−2.5. Individuals with T-score <−1 were considered to have low BMD.
The study participants were interviewed and clinically examined, and anthropometric measurements were taken. Then, they were informed to attend the BMD camp in prefixed spots on the specified scheduled dates. Three such camps were arranged, each camp covering two villages at a time. The participants underwent BMD estimation through calcaneal QUS (GE Mini Bone Densitometer, model no. 0402, made in Germany) and blood investigation for serum 25(OH) Vitamin D and serum total calcium level. The bone densitometer was operated by a trained technician. The result for each individual was system generated from the device immediately after the procedure. Thus, quality control for the device was ensured by the technician before each camp and in-between measurements according to the manufacturer's recommendations. Approximately 7.5 ml of blood was collected by a phlebotomist and sent to a reliable laboratory for investigation maintaining blood cold chain. The laboratory procedure employed for estimation of serum 25(OH) Vitamin D and serum total calcium was radioimmunoassay and spectrophotometry, respectively. The laboratory reports were distributed on the subsequent working day and necessary advice, and drugs were prescribed if required. Those with osteoporosis were referred to the nearest tertiary hospital.
The data entry and analysis were performed using statistical software SPSS (IBM SPSS Statistics for Windows, version 16.0). Descriptive statistics (mean ± standard deviation [SD] and median for the continuous variables and frequency in percentage for the categorical variables) were used to describe the sociodemographic, dietary pattern, sun exposure, tobacco use, menopausal status, and morbidity profile. One-way analysis of variance (ANOVA) was employed to test differences in Vitamin D level among the quartiles of sun index. Inferential statistics were used to determine the factors associated with low BMD. Results were considered significant at P ≤ 0.05 level.
| Results|| |
Background characteristics of the study population
Out of 260 participants, 103 (39.6%) belonged to the age group of 40–49 years. The mean (SD) age of the participants was 54.2 (10.2) years. Among them, only 97 (37.3%) were educated up to primary. According to the Modified B. G. Prasad 2017, 114 (43.8%) of the participants belonged to socioeconomic status Class III. Among the study participants, 184 (70.8%) had attained menopause. Approximately one-fourth of the study participants were predominantly involved in outdoor activities. Tobacco chewing was seen among one-fourth of the participants. On calculating BMI, it was observed that 13.5% were underweight and 51.2% were either overweight or obese. Furthermore, 26.2% were hypertensive and 30.4% were suffering from diabetes. Approximately 18% of the study participants had a previous history of osteoporotic fracture, while almost a similar count reported a positive family history of osteoporotic fracture.
Out of the study participants, 34 (13.1%) were screened positive for osteoporosis and 168 (64.6%) were screened positive for osteopenia. Overall, 77.7% were found to have low BMD [Table 1]. Mean (SD) BMD T-score among the study participants was −1.56 (0.61), with a median T-score value of −1.49. Kolmogorov–Smirnov and Shapiro–Wilk tests were employed which showed significance value more than 0.05 in both cases, thus implying normal distribution of T-scores.
|Table 1: Distribution of study participants according to their bone mineral density and Vitamin D level (n=260)|
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The mean (SD) Vitamin D level among the study participants was 26.49 (5.73) ng/ml. Tests for normality revealed normal distribution of data. A total of 194 (74.6%) had VDI (<30 ng/ml), including 13.5% who had deficient levels of Vitamin D (<20 ng/ml) [Table 1].
Data revealed a positive correlation of 0.67 (P < 0.05) between BMD T-score and Vitamin D levels [Figure 1].
|Figure 1: Scatter plot showing the correlation between bone mineral density T-score and Vitamin D levels among the study participants (n = 260).|
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The mean (SD) duration of daily sun exposure was 78.4 (55.1) min. There was a strong positive correlation of 0.71 (P < 0.05) between serum Vitamin D level and daily sun exposure. On calculating sun index, it was seen that there were significant differences in mean serum Vitamin D levels across the quartiles of sun index [Figure 2].
|Figure 2: Mean serum Vitamin D across various sun index levels (n = 260).|
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About 28% of the participants reported to have fish for 3 days in the past 7 days. Similarly, 89 (34.2%) stated to have egg yolk for 3 days in the past 7 days. Almost half (54.6%) of the participants did not consume milk or any of the dairy products in the past 7 days. It was seen that 148 (56.9%) participants had a diet score ranging from 6 to 10, while only 41 (15.8%) participants had a score from 11 to 16.
On multivariable analysis, it was observed that VDI (adjusted odds ratio [95% confidence interval] = 4.13 [2.12, 8.37]) was a significant predictor of low BMD after adjustment for poor education, decreasing diet score, menopause, presence of comorbidity, underweight as well as overweight [Table 2]. The calculated Nagelkerke R-square value is 0.436 and Cox and Snell R-square value is 0.402. The Hosmer–Lemeshow test (P = 0.55) is nonsignificant which indicates model fitness.
|Table 2: Binary logistic regression between low bone mineral density and some important variables (n=260)|
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| Discussion|| |
In our study, almost four-fifth of the women were found to have low BMD. An abysmal count of 13.1% had osteoporosis and 64.6% had osteopenia. The statistics are quite similar to a study by Dutta et al. conducted in Assam in 2015 among adults aged 40 years and above, where the prevalence of osteoporosis was 16% and osteopenia was 61.3%. Another study was conducted in Bangalore by Qureshi et al. from 2010 to 2013 among 1188 adults aged 40 years and above, where 11% of the females were reported to have osteoporosis and 51.6% had osteopenia. A study by Unni et al. in Pune in 2010 among women of similar age group gives a better picture of 31.4% osteopenia but is again high on the burden of osteoporosis (14.3%). Even the prevalence of osteoporosis and osteopenia is relatively higher when compared to large community-based studies conducted in other Asian countries.,, Thus, poor bone health is matter of immediate concern, and the scenario here is no better than in any part of the country.
Our study found that 74.6% of the women had VDI. This is lower than 99.7% of VDI, as reported by a study among adult women in the rural community of Ballabgarh development block in Faridabad in 2017. This may be attributed to the fact that in West Bengal, fish and egg consumption is more. Furthermore, a number of participants with overweight/obesity were low.
In our study, there was a strong positive correlation of 0.71 (P < 0.05) between serum Vitamin D level and daily sun exposure. This can be explained by the fact the sunlight is one of the important sources of Vitamin D. Exposure of the skin to sunlight initiates synthesis of Vitamin D which further helps in calcium absorption from the intestine and kidneys. A recent study conducted on Vitamin D and sun exposure among adults in a similar setting has suggested that a daily exposure of the hand including palm, neck, and feet to sunlight for 1 h would be adequate to maintain sufficient serum Vitamin D levels.
Our study found insufficient serum Vitamin D levels to be significantly associated with low BMD. Data revealed a positive correlation of 0.67 (P < 0.05) between BMD T-score and Vitamin D levels. Studies conducted across the globe showed similar associations., It is evident that Vitamin D plays a major role in acquiring and maintaining optimum bone health. However, our study failed to establish an association between low BMD and serum total calcium level. An explanation can be that poor calcium intake and resultant calcium deficiency state trigger a secondary increase in parathormone which increases bone resorption and suppression of bone formation. This mechanism is initiated to maintain a consistent level of calcium in the serum at the cost of bone health.
The presence of comorbidities, namely hypertension, diabetes, and hypothyroidism, as well as nutritional status of both underweight and overweight, has been found to have a detrimental effect on bone health. Studies have suggested that raised angiotensin II levels in hypertensive settings increase bone resorption and decrease mineralization. Metabolic alterations seen in diabetes also trigger impairments of calcium homeostasis and resultant accelerated bone resorption. Historically, obesity has been related to as a protective factor in bone health., Besides the fact that underweight individuals have thinner fragile bones, recent studies have demonstrated that adipose tissue may negatively impact bone health and thereby increase fracture risk as well.
The present study has its own strengths and limitations. It was a community-based study on bone health status among women. There is no such study in this part of the country as per researcher's knowledge because all such researches searched till now are clinic-based studies. Calcaneal QUS was employed as a screening tool for assessing the bone health status in the community. Furthermore, serum 25-hydroxy Vitamin D was investigated which is the most sensitive indicator of the individual's Vitamin D status and is an explanatory variable for BMD. However, other investigations such as serum alkaline phosphatase, parathyroid hormone, and calcitonin should be considered in further research. Another limitation is that, though data collection period was 12 months covering all the seasons of the year, analysis regarding the seasonal variation of diet was not done.
| Conclusion|| |
The findings of the study clearly indicate the existence of a high prevalence of poor bone health among women aged 40 years and above in our society. Conclusively, it may be asserted that poor bone health status is a neglected issue and stringent steps must be taken at all levels to overcome this. At the individual level, emphasis must be given on measures to maintain optimum serum Vitamin D levels. Promoting consumption of Vitamin D-rich food and daily exposure of the skin to sun are key to increase synthesis of Vitamin D in the body. Maintaining optimum body weight and prompt management of comorbidities are the other key areas which need constant advocacy. Furthermore, this calls for a prompt action at the policy level. There is a need of mass campaign to increase the awareness of our community regarding the prevention and control of poor bone health. Awareness or proper knowledge is a prerequisite for favorable practice. Provision for screening and early diagnosis of osteoporosis, framing of population-based program to provide affordable Vitamin D supplements, and Vitamin D-fortified food will health improve the situation at large. Further studies should be taken up to establish the associates of poor bone health on larger and different population groups. The role of individual morbidities on bone health needs to be addressed in future studies. Serum Vitamin D levels are implicated to play a crucial role in bone metabolism; however, its effect on the body in accordance with other important hormones such as thyroxine, parathormone, and calcitonin should be explored.
We acknowledge all the ASHAs, ANMs, and study participants for their valuable time.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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