Effects of the COVID-19 pandemic on serum vitamin D concentration in Korean children

PURPOSE

Social distancing policies and school closures in South Korea induced by coronavirus disease 2019 have raised concerns about a lower chance of exposure to sunlight in children and adolescents. This study investigates changes in the vitamin D status of children and adolescents following the pandemic.

METHODS

This retrospective study includes healthy children aged 3-18 years who visited Hanyang University Hospitals in Seoul or Guri during pre-coronavirus disease 2019 (COVID-19) and post-COVID-19 pandemic periods. August 2017 to July 2019 is defined as the pre-COVID-19 pandemic period, while the period from July 2020 to July 2021 is defined as post-COVID-19 or "during the pandemic." Propensity scores were used to match the prepandemic and pandemic groups 1:1 based on age, sex, season of blood collection, and body mass index z-score to compare vitamin D status among subjects.

RESULTS

Among 786 eligible children, 506 were matched using propensity scores. There were no significant differences in mean serum 25-hydroxyvitamin D (25(OH) D) levels (20.1±6.5 ng/mL vs. 19.9±6.3 ng/mL, P>0.05) or vitamin D deficiency rates (53.0% vs. 54.9%, P>0.05) between the prepandemic and pandemic groups. Seasonal analysis revealed lower mean serum 25(OH)D levels during the pandemic in winter/spring seasons in comparison to these levels in subjects in prepandemic winter/spring seasons (19.1±3.8 ng/mL vs. 17.2±3.7 ng/mL, P=0.006).

CONCLUSION

During the COVID-19 pandemic, Korean children and adolescents showed similar serum 25(OH)D levels and vitamin D status to the prepandemic period, with a significant decrease in these measures observed in winter/spring seasons only. Prolonged confinement, such as in pandemic circumstances, underscores the need for vigilant monitoring of vitamin D status and supplementation, particularly in high-risk seasons.

Changes in Vitamin D Status in Korean Adults during the COVID-19 Pandemic

The aim of this study was to investigate changes in 25(OH)D (25-hydroxyvitamin D) levels and in the vitamin D status of Korean adults before and during the coronavirus disease (COVID-19) pandemic. This study compared serum 25(OH)D levels before and after the pandemic in 1483 adults aged 19 years and older who were screened at a university hospital. Subjects were selected only from participants tested in the same season before and after the pandemic. The pre-COVID-19 testing period was from 1 March 2018 to 31 November 2019; the testing period in the COVID-19 era was from 1 June 2020 to 31 November 2021. The mean 25(OH)D level for all participants was 21.4 ± 10.2 ng/mL prior to the outbreak of COVID-19, which increased to 23.6 ± 11.8 ng/mL during the COVID-19 lockdown period (p < 0.001). The increase was particularly dramatic in elderly females (28.8 ± 12.3 ng/mL to 37.7 ± 18.6 ng/mL, p = 0.008). The prevalence of vitamin D deficiency decreased in both males (48.4% to 44.5%, p = 0.005) and females (57.0% to 46.0%, p < 0.001). In conclusion, 25(OH)D levels in Korean adults increased during the COVID-19 era, and the prevalence of vitamin D deficiency decreased accordingly.

Association between Blood Vitamin D Levels and Regular Physical Activity in Korean Adolescents

This study aimed to investigate the relationship between vitamin D levels and physical activity in adolescents using data from the Korea National Health and Nutrition Survey (KNHANES). The serum vitamin D concentrations were measured between 2008 and 2014 and analyzed. Adolescents aged 13 to 18 years comprised 4527 of the 61,370 participants surveyed. A final dataset including 2811 adolescents was obtained after those with missing data were excluded. Those who did not participate or only participated in 1−3 days of intense physical activity (p < 0.001), moderate physical activity (p = 0.002), and muscular exercise (weight training) (p < 0.001) showed a higher level of vitamin D deficiency than those who performed the same activities 4−7 days per week. Our results showed that most of the adolescents (76%) were vitamin D-deficient, and the risk was higher among high school than middle school students (odds ratio (OR) = 1.70, 95% confidence interval (CI) = 1.40−2.06; p < 0.001) and higher in girls than boys (OR = 1.43, 95% CI = 1.18−1.72; p < 0.001). Reduced participation in physical activity was correlated with vitamin D deficiency. Furthermore, vitamin D deficiency was associated with a lower frequency of participation in all forms of physical activity, and the association increased significantly with an increase in body mass index.

[Inflammatory Bowel Disease and Vitamin D]

Vitamin D contributes to bone metabolism and acts as an immune modulator for both innate and adaptive immunity. The serum level of vitamin D has been associated with inflammatory diseases, such as inflammatory bowel disease (IBD). In epidemiologic studies, IBD patients have been shown to have low levels of vitamin D. The suboptimal circulating levels of vitamin D in IBD patients may be caused by low exposure to sunlight, dietary malabsorption, and the impaired conversion of active metabolites (1,25[OH]₂D). Recent studies have demonstrated that vitamin D deficiency in IBD can increase the chance of disease recurrence, IBD-related hospitalization or surgery, and deterioration of quality of life. Supplementation with vitamin D is therefore thought to reduce the risk of flare-ups and the improvement of the quality of life in IBD patients. This review aims to summarize the latest knowledge on the effects of vitamin D deficiency on IBD and the possible benefits of vitamin D supplementation in IBD patients.

Factors Associated with Vitamin D Status Among Korean Female Adolescents

PURPOSE

The prevalence of vitamin D deficiency among female adolescents in South Korea is the highest in East Asia. Therefore, this study aims to identify factors associated with vitamin D status among female adolescents in South Korea.

DESIGN AND METHODS

This cross-sectional descriptive study was conducted using a data set from the fifth Korean National Health and Nutrition Examination Survey (2010-2012). Participants comprised 734 female adolescents aged 12-18 years. A general linear model using a complex samples design was employed.

RESULTS

The mean vitamin D level of the participants was 14.90 ng/mL. Among these participants, 87.6% had a vitamin D deficiency. As their age increased by one year, their vitamin D level decreased by 0.47 ng/mL. Female adolescents with a low household income had vitamin D levels lower by 1.88 ng/mL than those with a high household income. Vitamin D levels in female adolescents who skipped lunch was lower by 3.41 ng/mL than those who had lunch.

CONCLUSION

The prevalence of vitamin D deficiency among female adolescents in South Korea is considerable. The findings suggest that age, socioeconomic status, and skipping a meal were associated with vitamin D status in female adolescents, but physical activity was not.

PRACTICE IMPLICATIONS

As the findings of this study indicate, older female adolescents and those from lower household incomes may be at higher risk for lower levels of Vitamin D. Counseling female adolescents as to dietary measures to avoid vitamin D deficiency is advised. Preventive health for at risk female adolescents includes provision of health education and counseling.

Association of the Vitamin D Level and Quality of School Life in Adolescents with Irritable Bowel Syndrome

There is no treatment of choice for irritable bowel syndrome, which affects up to 20% of school-aged children. This cross-sectional study evaluated the difference in the average vitamin D level between subtypes of irritable bowel syndrome, and the relationship between the vitamin D level as well as the severity of irritable bowel syndrome symptoms. We included 124 adolescents aged 10–17 years (68 boys, 56 girls; mean age 12.29 ± 1.92 years) from 2014 to 2016. Patients with irritable bowel syndrome were diagnosed by Rome III criteria and classified by clinical manifestation: irritable bowel syndrome with constipation (n = 29), irritable bowel syndrome with diarrhea (n = 63), and irritable bowel syndrome with constipation and diarrhea (n = 32). The severity of irritable bowel syndrome symptoms and school absence were evaluated. Vitamin D levels were measured by serum 25-hydroxyvitamin D. The chi-square test and analysis of variance were used. The patients’ average vitamin D level was 16.25 ± 6.58 ng/mL. There was a significant negative association of the 25-hydroxyvitamin D level with symptom severity and school absence (p = 0.022 and p < 0.001, respectively). Vitamin D supplementation could be considered as a choice of therapeutic method.

Laboratory confirmation of the effect of occupational sun exposure on serum 25-hydroxyvitamin D concentration

Vitamin D concentration is known to correlate with various parameters. A major source of vitamin D is synthesis in the skin; thus, the duration of sun exposure is known to correlate with serum vitamin D levels. We compared serum levels of vitamin D between 2 occupational groups in Korea: the fisherman group, the most sun-exposed, and the general occupation group, relatively less sun-exposed. This study was conducted on 140 healthy fishermen and 140 healthy residents with various occupations, all of whom resided in the southernmost region of Korea, from June to August 2016. We compared serum concentrations of 25-hydroxyvitamin D (25(OH)D) in both occupation groups by gender and age and suggested vitamin D reference interval for the region. Mean serum 25(OH)D concentrations in the general occupation and fisherman group were 13.60 ± 6.43 and 23.74 ± 8.88 ng/mL, respectively. Mean serum concentration of 25(OH)D was 1.7 times higher in the fisherman group compared with the general occupation group, which was statistically significant (P < .001). Approximately 98% of subjects in the general occupation group and 78% of subjects in the fisherman group demonstrated either vitamin D insufficiency or deficiency. Calculated serum 25(OH)D reference interval for all subjects in our study was 3.8 to 44.4 ng/mL. Despite exposure to a large amount of sunlight, 78% of subjects in the fisherman group presented with either vitamin D deficiency or insufficiency. By taking laboratory measurements of serum 25(OH)D concentrations in fisherman, who were expected to have the highest vitamin D concentrations in Korea, this study could be epidemiologically useful.

Relationship between vitamin D levels and intravenous immunoglobulin resistance in Kawasaki disease

Purpose

Vitamin D is associated with various pathological conditions such as cardiovascular diseases and cancer. We investigated the relationship between vitamin D and Kawasaki disease (KD).

Methods

We performed a retrospective review of the medical records of patients with KD between February 2013 and March 2016 in Daegu Fatima Hospital. Study participants were grouped according to vitamin D serum concentration. Group 1 included patients with 25(OH)-vitamin D ≥20 ng/mL. Group 2 included patients with 25(OH)-vitamin D <20 ng/mL. We analyzed the clinical characteristics and laboratory data of the 2 groups.

Results

Of the 91 patients, 52 were included in group 1, and 39 in group 2. Group 1 patients had significantly higher levels of calcium, phosphate, albumin and sodium than group 2 patients did. There were no differences in clinical characteristics, but the proportion of patients with polymorphic rash was significantly higher in group 2. Resistance to intravenous immunoglobulin was more frequent in group 2 (P=0.023). No significant difference in the incidence of coronary artery complications was observed.

Conclusion

Low vitamin D levels are associated with resistance to intravenous immunoglobulin therapy in KD. Vitamin D deficiency might be a risk factor for immunoglobulin resistance in KD.

The serum level of 25-hydroxyvitamin D for maximal suppression of parathyroid hormone in children: the relationship between 25-hydroxyvitamin D and parathyroid hormone

Purpose

Serum level of 25-hydroxyvitamin D (25-OHD) is considered as the most appropriate marker of vitamin D status. However, only a few studies have investigated the relationship between 25-OHD and parathyroid hormone (PTH) in children. To this end, this study was aimed at evaluating the lowest 25-OHD level that suppresses the production of parathyroid hormone in children.

Methods

A retrospective record review was performed for children aged 0.2 to 18 years (n=193; 106 boys and 87 girls) who underwent simultaneous measurements of serum 25-OHD and PTH levels between January 2010 and June 2014.

Results

The inflection point of serum 25-OHD level for maximal suppression of PTH was at 18.0 ng/mL (95% confidence interval, 14.3–21.7 ng/mL). The median PTH level of the children with 25-OHD levels of <18.0 ng/mL was higher than that of children with 25-OHD levels ≥ 18.0 ng/mL (P<0.0001). The median calcium level of children with 25-OHD levels<18.0 ng/mL was lower than that of children with 25-OHD levels≥18.0 ng/mL (P=0.0001). The frequency of hyperparathyroidism was higher in the children with 25-OHD levels<18.0 ng/mL than in the children with 25-OHD levels≥18.0 ng/mL (P<0.0001). Hypocalcemia was more prevalent in the children with 25-OHD levels<18.0 ng/mL than in the children with 25-OHD levels≥18.0 ng/mL (P<0.0001).

Conclusion

These data suggest that a vitamin D level of 18.0 ng/mL could be the criterion for 25-OHD deficiency in children at the inflection point of the maximal suppression of PTH.