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Rickets in Mongolia - July 2013

Prevalence of classic signs and symptoms of rickets and vitamin D deficiency in Mongolian children and women

  • Nutrition Research Center, Public Health Institute, MOH, Mongolia

Abstract

In order to assess the current nutrition status of Mongolian population, including rickets and vitamin D deficiency of children and women, the Fourth National Nutrition Cross-Sectional Survey was conducted in 21 aimags (provinces) of 4 economic regions of the country and capital city Ulaanbaatar in 2010. Children of age under five years, and non-pregnant women of reproductive age were used as subjects for assessing rickets and vitamin D deficiency. A total of 400 households were randomly selected from each of 4 economic regions and Ulaanbaatar city. Clinical examinations were performed on 706 children of age under five years. Interviews were used to assess vitamin D supplement use. The serum level of 25-hydroxyvitamin D was measured in 524 children aged 6–59 months and in 867 women of reproductive age. This survey found that 21.8% of children had vitamin D deficiency, 20.6% had low vitamin D reserve, and 30.0% of women had vitamin D deficiency and 22.2% had low vitamin D reserve. The prevalence of vitamin D deficiency in children (35.0%, 95% CI, 24.7–47.0) and women (54.9%, 95% CI 45.5–64.0) in the Eastern Region was (35.0%, 95% CI, 24.7–47.0) significantly higher than in the Western, Khangai, Central Regions, and Ulaanbaatar. Further it was found that 27.4% of children under-two years had received vitamin D supplementation. The proportion of children, who did not receive vitamin D supplementation had a higher prevalence of vitamin D deficiency than that of the children of the Eastern Region. None of the women who were involved in this survey had received vitamin D supplementation; 10.2% of them had delivered in the past 12 months, and 22.5% were breastfeeding. The prevalence of classic signs and symptoms of rickets were commonly reported among children of age under five, and skeletal abnormalities more commonly reported in children aged 12–47 months.

In conclusion, there is a high prevalence of classic signs and symptoms of rickets in children of age under five years. Vitamin D supplementation in adequate doses for the prevention and treatment of rickets in children is insufficient. Thus, a trial survey is needed to assess the safe and effective doses of vitamin D supplementation necessary for the maintenance of normal serum 25-hydroxyvitamin D concentrations in Mongolian children, and women. In addition, a vitamin D food fortification program is required.

This article is part of a Special Issue entitled ‘Vitamin D Workshop’.

Highlights

► There is high prevalence of classic signs and symptoms of rickets in Mongolian children under five.

► Bone deformation of rickets is common in children above one year.

► The prevalence of vitamin D deficiency is high in children and reproductive age women, in Mongolia.

► Vitamin D supplementation in “adequate doses” is insufficient in Mongolian children.

► A trial survey is needed to assess the safe and effective doses of vitamin D supplementation in Mongolian children and women.
     A vitamin D food fortification program for children and pregnant women is required.

Keywords

  • Rickets;
  • Vitamin D;
  • Deficiency;
  • Supplementation;
  • Children;
  • Women;
  • Mongolia

1. Introduction

Vitamin D deficiency causes rickets in infants and young children, and osteomalacia in adults. The concentration of 25-hydroxyvitamin D 25(OH)D in blood is regarded as the best indicator of vitamin D status, because it is quantitatively related to the supply of vitamin D taken in over the preceding weeks 1. There is as yet no consensus about the threshold level of 25(OH)D that indicates vitamin D deficiency in children. However, researchers have suggested that severe chronic vitamin D deficiency 25(OH)D level less than 15 ng/ml can lead to overt skeletal abnormalities in children that is typically defined as rickets 2, 3, 4 and 5. However, there is a large number of infants, children, and adolescents who are vitamin D insufficient but have no apparent skeletal or calcium metabolism abnormalities 6.

Vitamin D deficiency and associated rickets are re-emerging as a major public health problem in some developed and developing countries 7 and 8. Exclusive breastfeeding, with inadequate vitamin D supplementation in the mother and baby, has been concluded to be the most important risk factor 9, 10 and 11.

Vitamin D deficiency is highly prevalent disorder in Mongolia. According to a Survey on Investigation of the Etiology of Rickets in Mongolian Children and the Development of Strategies for Prevention conducted with WHO support in 2000–2003, 37.1% of pregnant women, 30.5% of women who gave birth, and 41% of children under five had vitamin D deficiency, 25(OH)D < 18 nmol/L, 49.1% had vitamin D binding protein (DBP) deficiency, and dietary calcium intake was insufficient 12 and 13. Furthermore, the Third National Nutrition Survey in 2006 reported that 41% of children had vitamin D insufficiency 25(OH)D < 18–23 nmol/L and, 38.3% of non-pregnant women had vitamin D deficiency 25(OH)D < 18 nmol/L 14. Thus, the Government of Mongolia has been implementing a National Strategy to prevent mother and child from micronutrient deficiency since the year 2000 15. There is no vitamin D food fortification at present. Therefore, vitamin D supplementation (D2, 50,000 IU) has only been distributed to children from birth to 2 years of age once per month in cold seasons. Children with rickets have usually been treated in Mongolia with this form of vitamin D in a dose of 50,000 IU orally (5 or 6 tablets) 16.

In 1994–1996, the National vitamin D supplementation prevalence rates were between 46 and 56% in children under-three years 17. Thus, the Government of Mongolia has been expanding National vitamin D supplementation of children since 2009, and aimed to re-evaluate the prevalence of clinical signs and symptoms of rickets, and vitamin D deficiency in children and women through the Fourth National Nutrition Survey in 2010.

2. Subjects and methods

The Fourth National Nutrition Survey was a cross-sectional survey, and it was conducted in 21 aimags (provinces) of 4 economic regions of the country and capital city Ulaanbaatar between July and September 2010. A total of 400 households were randomly selected from each of the 4 economic regions and Ulaanbaatar city. Population groups most vulnerable to malnutrition, such as children under the age of five, and non-pregnant of reproductive age women were used as subjects for assessing rickets and vitamin D deficiency.

Clinical examination was performed in 706 children to tabulate the classic signs and symptoms of rickets. Interviews were used to assess vitamin D supplement use.

2.1. Serum 25-hydroxyvitamin D analysis

Serum level of 25-hydroxyvitamin D was measured in 524 children aged 6–59 months and in 867 reproductive age women with a double antibody sandwich enzyme-linked immunosorbent assay using Immuno Mini NJ-2300 micro plate reader (Japan) at 450 nm. The assay for 25(OH)D ranged from 2 to 60 nmol/L. At the laboratory of the Public Health Institute of Mongolia, the normal range for human subjects is 25–140 nmol/L 18, 19, 20 and 21. A serum value of 18–23 nmol/L indicated the presence of minimum vitamin D reserves and values below 18 nmol/L were defined as indicating vitamin D deficiency 18, 19, 20 and 21.

2.2. Data analysis

Analyses were carried out using PASW statistics 18.0 and EPI INFO 2000 software. The statistical significance of differences in prevalence and measures of central tendency between subgroups were calculated using, 95% confidence interval.

2.3. Ethical considerations

The survey methodology was discussed by the Ethical Committee under the auspices of the Ministry of Health on 4th June 2010 and was granted approval. Written and oral informed consent was obtained from heads of households and all individual participants randomly selected to participate in the survey.

3. Results

3.1. Prevalence of classic signs and symptoms of rickets in children under 5 years of age

In this survey, the classic signs and symptoms of rickets in children under-five was as follows: 31% – “sweating on their forehead during sleeping and breastfeeding”, 19.5% – “urine smelling”, 9.4% – “occipital alopecia”, 2.8% – “soft fontanel”, 0.8% – “craniatabes”, 9.4% – “Olympic forehead”, 18.3% – “cranial deformation”, 7.4% – “rosary of rickets”, 11.8% – “Harrisons groove”, 9.5% – “pigeon chest”, 3% – “symptom of bracelet”, 5.4% – “frog abdomen”, 0.2% – “spinal deformation”, 15.7% – “bowing of the legs”, 9.6% – “X leg”, 25.6% – “hard swollen joints of knee”, 0.9% – “hard swollen joints of anklebone”, and 6.6% – “unclosed fontanel”. Excessive perspiration during sleeping and breastfeeding, urine smelling, soft fontanel, occipital alopecia, and craniatabes signs were more commonly observed in infants aged less than 12 months, whereas other skeletal abnormalities were commonly reported in children aged 12–47 months.

3.2. Prevalence of vitamin D deficiency and low vitamin D reserve, and serum 25-hydroxyvitamin D level in children, and women

This survey found that 21.8% (95% CI 16.4–28.4) of children had vitamin D deficiency, and 20.6% (95% CI 16.8–25.0) had a low vitamin D reserve. Thirty-five percent of the children in the Eastern Region had vitamin D deficiency (95% CI, 24.7–47.0), and it was significantly higher than the prevalence of vitamin D deficiency in the Western, Khangai, and Central Regions. Age specific analysis showed that 30.2% (95% CI 18.9–34.5) of children aged 48–59 months had vitamin D deficiency and 33.6% (95%, CI 24.2–44.6) of children aged 36–47 months had vitamin D insufficiency. The prevalence of vitamin D deficiency and insufficiency among children of those age groups was significantly higher than the prevalence of vitamin D deficiency and insufficiency among children of other age groups.

With respect to supplementation, vitamin D deficiency was found in 23.1% (95% CI 17.1–30.5) of children who did not receive any vitamin D supplementation and 18.8% (95% CI 11.1–30.2) of the children who received supplementation. It was found that in vitamin D sufficient children, the mean serum 25(OH)D concentration was 48 ± 1.6 nmol/L {range, 19–279 nmol/L}, whereas in vitamin D deficient children, the mean serum 25(OH)D concentration was 12. ± 0.4 nmol/L {range, 1.5–18.3 nmol/L}. Also in children with low vitamin D reserve, the mean serum 25(OH)D concentration was 21 ± 0.2 nmol/L {range 17.4–24.5 nmol/L}.

In this survey, 30.0% (95% CI 24.9–35.6) of reproductive age women had vitamin D deficiency and 22.2% (95% CI 18.6–26.3) had low vitamin D reserve. It was found that, 10.2% of reproductive age women had delivered in the past 12 months, and 22.5% were breastfeeding, and all surveyed women did not receive vitamin D supplementation. With respect to Region, 54.9% (95% CI 45.5–64.0) of women in Eastern Region had vitamin D deficiency which was significantly higher compared to Khangai and Central Regions, and Ulaanbaatar. In vitamin D sufficient women, the mean serum 25(OH)D concentration was 77.9 ± 1.7 nmol/L, whereas in vitamin D deficient women, the mean serum 25(OH)Df concentration was 10.8 ± 0.6 nmol/L {range, 1.4–17.7 nmol/L}.

3.3. Relationship between vitamin D supplementation and prevalence of vitamin D deficiency

This survey found that 27.4% of children under-two years received vitamin D supplementation between October 2009 and the time of the interview. 60.2% of those children received a high-dose vitamin D2 tablets. 28.4% of them were received only one tablet (50.000 IU) of high-dose vitamin D2. According to the recommendation of Ministry of Health of Mongolia, only 8.4% of children received 7 or more tablets of vitamin D2 which would meet the dose to prevent children from rickets in cold seasons or a treatment dose for children with rickets. It was found that only 13.9% of young children received vitamin D supplementation in the Eastern Region. In addition, this survey found that the proportion of children, who did not receive vitamin D supplementation and prevalence of vitamin D deficiency, is higher in the Eastern Region.

3.4. Relationship between vitamin D deficiency and prevalence of classic signs and symptoms of rickets

It was found that 44.4% of the vitamin D deficient children have no classic signs and symptoms of rickets whereas, 55.6% of those children had 1 and 8 classic signs and symptoms of rickets. Also 42.2% of the children with low vitamin D reserves have any classic signs and symptoms of rickets whereas 57.8% of these children had 1 and 7 classic signs and symptoms of rickets.

4. Discussion

The finding of the current survey showed that rickets and vitamin D deficiency is still a public health problem in Mongolia. This survey found that, excessive perspiration during sleeping and breastfeeding, soft fontanel, occipital alopecia, and craniatabes were more commonly observed in infants aged less than 12 months, whereas other skeletal abnormalities were common reported in children aged 12–47 months. As compared to the “Third nutritional survey” result 14, prevalence of “occupational alopecia”, “cranial deformation”, “Harrison's groove”, “bowing of the legs” and “hard swollen joints of knee” signs were increased.

As compared to the “Third national nutrition survey” results, the prevalence of vitamin D insufficiency is increased among reproductive age women, whereas the proportion of children with vitamin D deficiency and low reserve of vitamin D are similar with the previous survey results 14. The third national nutrition survey results showed that there was no region specific difference in the prevalence of vitamin D deficiency among young children. But, the current survey results showed that the prevalence of vitamin D deficiency among young children in Eastern Region was significantly higher than their counterparts living in Khangai, and Central Regions.

The current survey found that, only 13.9% of young children in the Eastern Region received vitamin D supplementation. The proportion of children, who did not receive vitamin D supplementation and prevalence of vitamin D deficiency, is higher in the Eastern Region. Vitamin D deficiency was found in 23.1% of children who did not receive vitamin D supplementation and 18.8% of those who received the supplementation. Also the proportion of children with vitamin D deficiency and low vitamin D reserve was more common among children older than 2 years, which is probably related to a vitamin D supplementation for less than 2 year old children. According to the recommendation of Ministry of Health of Mongolia, only 8.4% of children received 7 or more tablets of vitamin D2 which would meet the dose to prevent children from rickets in cold seasons or a treatment dose for children with rickets. These findings suggest that rickets and vitamin D deficiency in Mongolian children might be related with the safe and effective doses of vitamin D insufficient supplementation.

Researchers have suggested that a newborn's 25-hydroxyvitamin D 25(OH)D concentration is approximately one-half that of it's mother's 25(OH)D 22. A risk factor for poor vitamin D status in early infancy is maternal vitamin D deficiency during pregnancy, results in an inadequate maternal transfer of vitamin D to the fetus and low infant stores 23, 24 and 25. Thus, our survey findings of women of reproductive age suggests that the rickets and vitamin D deficiency in early infancy might be related with maternal poor vitamin D status during pregnancy and for breastfeeding mothers. Also the poor vitamin D status in Mongolian women might be related with lack of vitamin D supplementation.

Researchers suggested that the severe chronic vitamin D deficiency 25(OH)D level less than 5 ng/ml (12 nmol/L) leads to overt skeletal abnormalities in children that is typically defined as rickets 2, 3 and 5. According to the previous survey results, vitamin D deficiency, and low vitamin D reserve in Mongolian children were significantly correlated with classical signs of rickets 12, 13 and 14. Furthermore, vitamin D deficiency and insufficiency were determined in children and mother in Iran 26, 27 and 28, Tehran 29, China 30 and 31, Egypt 32, Pakistan 33 and 34, India 35, and Turkey 36.

Vitamin D experts have suggested that a circulating level of 25-hydroxyvitamin D of >75 nM/L, or 30 ng/mL, is required to maximize vitamin D's beneficial effects for health 37. In addition, Norman and Bouillon suggested that the blood concentration of vitamin D should at the very least meet or hopefully exceed a minimum desirable serum concentration of 50 nM/L (or 20 nm/ml) 38. According to our survey finding, in vitamin D sufficient children, the mean serum 25(OH)D concentration was 48.2 ± 1.6 nM/L {range, 19.1–279 nM/L}, whereas in vitamin D deficient children, the mean serum 25(OH)D concentration was 12.7 ± 0.4 nmol/L {range, 1.5–18.3 nmol/L}. Eventually, in vitamin D sufficient women, the mean serum 25(OH)D concentration was 77.9 ± 1.7 nmol/L, whereas in vitamin D deficient women, the mean serum 25(OH)D concentration was 10.8 ± 0.6 nmol/L {range, 1.40–17.7 nmol/L}. Thus, these findings show that the blood concentration of 25(OH)D in Mongolian children and women is very low.

Acknowledgements

The 2010 Fourth National Nutrition Survey was conducted by the researchers of the Mongolian Nutrition Research Centre of the Public Health Institute with the technical assistance of Dr. Bradley A. Woodruff, who is an international consultant. Also we received financial support from the United Nations Children's Fund, World Health Organization, World Vision, and the Mongolia International NGO, and Ministry of Food, Agriculture, and Light Industry. We express our sincere appreciation to the Fourth National Survey Coordinating Committee of the Ministry of Health, the Survey team members and Laboratory analysis team.

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Corresponding author contact information

Correspondence address: Nutrition Research Center, Public Health Institute, MOH, Peace Avenue, 17 Street, Baynzyrch District, Ulaanbaatar 1381, Mongolia. Tel.: +976 11 4586 45; fax: +976 11 4586 45.

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