Reference Interval of Vitamin D of Coastal Fishermen in Cox's Bazar District of Bangladesh
Condition: Vitamin D Deficiency
MeSH terms: Vitamin D Deficiency
Study type: Observational

Summary: 
      Lack of adequate sun exposure due to urbanization is prone to hypovitaminosis D. Vitamin D
      (25-hydroxyvitamin D) deficiency is now a major health concern in the western world. Recent
      data suggest that Vitamin D level in the Bangladeshi population is also very low. However,
      the cutoff value used to determine vitamin D deficiency is not yet validated for our ethnic
      group; we also don't know the optimal vitamin D level for our population. Before coming to
      any firm conclusion regarding nationwide vitamin D deficiency, we must know the Optimal range
      of serum Vitamin D for our people of Bangladesh. As sunlight is the primary source of vitamin
      D and adequate sun exposure alone is sufficient to produce enough vitamin D to maintain the
      physiological demand without producing toxicity. According to Holick's rule, exposure to
      sunlight at the face and both arms for 25 min, 3 times a week should maintain adequate
      vitamin D status. In Indonesia, it was found that after exposure to sunlight at this specific
      time and duration for 6 weeks, the mean 25(OH)D levels of participants increased from 59
      nmol/L at the baseline to 84 nmol/L.In India, exposure to sunlight for 30 minutes, between 11
      am and 2 pm, three times a week, is sufficient to maintain adequate serum vitamin D
      concentration. Therefore it could be assumed that healthy subjects without any risk factors
      for vitamin D deficiency and having adequate sun exposure should maintain an Optimal serum
      vitamin D concentration. Here Optimal means a range where there will be no features of
      insufficiency or toxicity. In this cross-sectional study, we want to find out the serum
      vitamin D level of such a population, representing the Optimal level of vitamin D for
      Bangladeshi people.
    

Detailed description: 
      Vitamin D is the sunshine vitamin produced on this earth for more than 500 million years.
      This is produced in humans by sunlight. Sunlight is the main source of vitamin D, and
      adequate sun exposure alone is sufficient to produce enough vitamin D to maintain the
      physiological demand without producing toxicity. According to Holick's rule, exposure to
      sunlight on the face and both arms for 25 min, 3 times a week, should maintain adequate
      vitamin D status. In Indonesia, it was found that after exposure to sunlight at this specific
      time and duration for 6 weeks, the mean 25(OH)D levels of participants increased from 59
      nmol/L at the baseline to 84 nmol/L.In India, exposure to sunlight for 30 minutes, between 11
      am and 2 pm, three times a week is sufficient to maintain adequate serum vitamin D
      concentration. Lack of adequate sun exposure as a consequence of urbanization prone human
      races to a threat of hypovitaminosis D. Vitamin D (25-hydroxyvitamin D) insufficiency and its
      impending consequence on health is now the subject of important concern and controversy. The
      optimal value of vitamin D substantially differs among populations depending upon
      environmental, cultural and racial factors. However, the definition of vitamin D
      insufficiency is still not out of controversy, mostly cutoffs of <50 nmol/L of serum
      25-hydroxyvitamin D (25(OH)D) level is considered as "vitamin D deficiency" state, 50 to 74.9
      nmol/L denotes "insufficiency" and ≥75 nmol/L considered as "sufficiency".

      With the falling of serum25 (OH)D beyond a certain point, absorption of calcium from the gut
      decreases, which leads to a surge of parathyroid hormone (PTH) secretion, which in turn
      stimulates the conversion of 25(OH)D to 1,25(OH)2D to keep calcium at a normal limit. Thus, a
      higher value of PTH could be considered as a surrogate marker of vitamin D insufficiency.
      Serum 25(OH) D below the level of 75-100 nmol/L has an inverse correlation with PTH
      concentration; beyond this point, serum intact PTH concentration remains in a plateau state.

      Based on these definitions, the whole world faces a pandemic of vitamin D
      deficiency/insufficiency. According to recent studies, the prevalence of vitamin D deficiency
      has been found between 30% and 100% in different communities. This picture is similar in the
      USA, Europe, South East Asia and the Middle East. In India, the prevalence of Vitamin D
      deficiency is around 70%-100% in the general population. Baidya et al. (2012) studied 40
      healthy Indian physicians in Calcutta. Around 97.5% of subjects had low vitamin D. Mean age
      and meant 25(OH)D levels of that cohort were 52.22 ± 10 years and 13.02 ± 4.77 ng/ml
      (32.50±11.91 nmol/L). Vitamin D deficiency was found in 92.5% of participants. Though
      available data in Bangladesh are confined to female subjects only, the scenario is not
      different. More than ninety-nine percent of Bangladesh female garment workers were vitamin D
      insufficient in a study.

      This picture is alarming because, in addition to its deleterious effect on the
      musculoskeletal system, vitamin D deficiency is also linked with many other medical issues
      like cardiovascular disease, malignancy, neuromodulation, diabetes, and metabolic syndrome
      several autoimmune diseases (such as multiple sclerosis, Crohn's disease and ulcerative
      colitis) and certain infectious diseases, such as tuberculosis. Vitamin D supplementation is
      also a key component in the hierarchy of management of Chronic Kidney Disease-Mineral and
      Bone Disorder.

      However, the caveat of all of those studies done in Bangladesh and neighbouring countries
      like India and Pakistan is that the cutoff value used to determine vitamin D deficiency or
      insufficiency has not yet been validated for the corresponding population. Before reaching a
      firm conclusion about epidemics of vitamin D deficiency and planning for supplementation
      programs, the cutoff value of vitamin D deficiency/insufficiency of the Bangladeshi
      population must be validated. The optimal level of vitamin D for the Bangladeshi population
      should also find out.

      Rationale: Maintenance of adequate vitamin D levels undoubtedly is an important human health
      issue. It helps prevent many chronic diseases, which in fact are in addition to its principal
      role in maintaining appropriate blood calcium levels. To get the optimum beneficial effects
      of vitamin D, including prevention of many potential adverse health effects caused by
      deficient vitamin D, circulating 25(OH)D levels should be within the normal range. Vitamin D
      varies depending on various factors like exposure to the sun, age, race, body mass index,
      lack of exercise etc. The cutoff value for deficiency and insufficiency also varies between
      studies. Several studies using prescribed cutoff values of vitamin D deficiency reveal an
      epidemic of vitamin D deficiency in our country, despite abounded sunlight due to the
      proximity of the equator. However, no study was done previously in Bangladesh to determine
      the Optimal value of vitamin D representative of this population. The deficiency and
      insufficiency levels are ignorant and when to intervene is also not known. That is why it is
      important to conduct this exploratory study. It will help to assume the optimal reference
      range of serum vitamin D for the Bangladeshi population. That will give a clearer picture of
      the actual burden of vitamin D deficiency in Bangladesh and guide them to treat them and take
      necessary preventive measures at the national level.
    

Intervention name(s): Serum vitamin D assay
Intervention type(s): Diagnostic Test
Intervention description(s): Trained phlebotomists will collect 10 cc of a Blood sample. Specimen will be preserved at -40ºc for batch analysis.
S Vitamin D, S iPTH, S Calcium, S Alkaline Phosphatase, S PO4, S Mg, S Albumin and S Creatinine will be done in BIRDEM laboratory. Vitamin D will be assayed by The ARCHITECT 25-OH Vitamin D assay system: Vitamin D will be assayed by The ARCHITECT 25-OH Vitamin D assay system: The ARCHITECT 25-OH Vitamin D assay is a chemiluminescent micro-particle immunoassay (CMIA). This technology is used for the quantitative analysis of 25(OH) D and aid in the assessment of vitamin D sufficiency.
Other intervention name(s): Serum iPTH assay
Intervention MeSH terms: Vitamin D
Observational model: Ecologic or Community
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Adequately sun-exposed healthy population: Healthy fishermen with at least 30 minutes of
        sun exposure between 11 am and 2 pm, three times a week for the preceding 6 months.

        All male aged 18 to 65 years

        Inadequately sun-exposed healthy population: Urban, office-based workers or homemakers,
        both male and female, who will come for a routine health check-up in the BIRDEM outpatient
        department, and health care workers of selected hospitals of Dhaka. Both male and female
        aged 18 to 65 years.
      
Biospecimen description: 
      serum
    
Keywords: Vitamin D; Bangladesh; Optimal Level; Coastal fishermen; Parathyroid Hormone; Reference interval